Category Archives: Age of Earth

100 Reasons the Earth is Old (reblogged from Age Of Rocks)

I am posting this page from Jonathan Baker’s Age of Rocks here for several reasons. It is an extremely useful resource, well researched and well-written; the author addresses creationists with humanity and respect, even as he demolishes their position; and the author himself is a committed Christian (why that should matter to me, a free-thinking atheist, is something I explain below).

Edinburgh to Siccar Point June-Jly 2012 048

Siccar Point. Horizontal Devonian sandstone over uptilted Silurian greywacke. Click and re-click to enlarge

The evidence presented ranges from tree rings to topography to sedimentology to physical geography to archaeology and anthropology to geochemistry to the fossil record to radiometric dating to astrophysics. Many of these are topics I have touched on, for example in my discussions of the unconformity at Siccar Point, and the slowly cooled multiple lava flows and palaeosols of the Giants’ Causeway.

In each case, the reasoning is briefly described, with links to more detailed discussions, many framed specifically to refute creationist claims. By relegating those claims to second place, the author avoids the common mistake of teaching the very error that he is warning against. At the same time, he pays a respectful attention to his opponents, for reasons that he explains elsewhere in his blog, even as he dismantles their arguments.

Like the authors of EvoAnth  and Leaving Fundamentalism, the author is at present a graduate student; welcome examples of how the web is democratising discourse, and how young scientists and educators are using the opportunity.

I commend this piece to all those who have to deal with creationism in schools and elsewhere, alongside such classics as 29+ Evidences for Macroevolution and Index to Creationist Claims, and hope that the author will continue to update and add to it as his own career progresses.


Giants’ Causeway: interbasaltic laterite palaeosol between lava flows at The Chimneys. Click and reclick to enlarge

Like Dennis Venema at Biologos and Robert Wiens at Radiometric Dating – A Christian Perspective, the author is a committed Christian, thus helping to give the lie to the claim that Christian belief requires biblical literalism and the rejection of established science. This matters, since as I have argued before inviting creationists to abandon their deepest convictions is not likely to be the best way to change their minds. Research at Glasgow  agrees with me on this. Life science entry classes there contain a sprinkling of creationists, most of whom abandon their creationism during the course, but without necessarily renouncing their religion. I should for completeness state my own view on religion, which is that believers face major problems in accepting reality. But they are their problems, not mine, and it is not my place to tell them how to deal with them.

I have one small technical quibble. Paragraphs 73 and 74 seem, for reasons of brevity, to run together separate things under the heading “argon-argon dating”. These are: Ar-36/Ar-40 comparisons, used to subtract out the contribution of any argon initially present; Ar-39/Ar-40 that uses Ar-39, produced from K-39 by irradiating the sample, as a proxy for K-39 and hence for K-40 (this is what is usually meant by “argon-argon dating”); and finally, Ar-39/Ar-40 combined with controlled heating to distinguish endogenous Ar-40 (which will be released at the same temperature as the Ar-39) from so-called “parentless” Ar-40 that has diffused in from other rocks, which will be released more readily.

But I digress, and it is time to let Jon speak for himself:

100 Reasons the Earth is Old

How do we know the Earth is older than literalistic readings of the Bible seem to imply?

Nicolas Steno, pioneer in sedimentology and stratigraphy

Nicolas Steno (1638–1686), the Catholic bishop who formulated foundational principles in stratigraphy, paleontology, and even crystallography.

Geologists have been wrestling with this question for centuries, especially those pioneers in the Earth sciences (e.g. Nicolas Steno, William Buckland, Hugh Miller, Thomas Chalmers, and even Charles Darwin) who were also devout clergymen or at least trained in natural theology. The 19th century in particular may be characterized by the massive, interdisciplinary effort that sought to answer the question scientifically: how old is the Earth? But it was not until the mid 20th century that all efforts began to converge on the value we accept today: 4.56 billion years.

Today, a resurgence of young-Earth creationism has many persuaded that science, when applied faithfully, still supports a much smaller age—close to only 6,000 years. While the arguments behind this movement are not convincing to professional geologists, as I’ve sought to elucidate on this blog, their popularity highlights the need to summarize coherently the positive evidences in favor of ‘deep time’. Below, I have compiled what I deem the 100 most convincing reasons—in no particular order—that the Earth is not less than 10,000 years old.

Those readers from a young-Earth background might be quick to point out that many of the evidences listed below have been refuted by creation ministries in their article databases. But that’s no coincidence. Those article databases are primarily built to rationalize to what are indeed strong evidences against the young-Earth position. So please note, I am keenly aware of those counter-arguments, and therefore I encourage you either to follow the links to in-depth discussions of each evidence or to contact me directly about why I find such counter-arguments unsatisfactory.

How do we know from geology that the Earth is greater than 10,000 years old?

  1. Tree-ring “long counts” from California, Central Europe, New Zealand, and Scandinavia extend up to ~13,000 years. These chronologies are constructed from hundreds of individual trees that overlap, so that even if a tree did produce multiple rings during a growth season, the ‘extra years’ would disappear in the correlation process. Even John Woodmorappe has written that these tree-ring chronologies cannot be explained by multiple rings being produced in a single year or the mismatch of individual tree records.
  2. treering

    Annual bands in the cross section of a temperate tree (original image here).

    The oldest individual bristlecone pine trees date to ~5,000 years old by dendrochronology (ring counting), which is older than the traditional date for Noah’s flood. Since we have no reason to suspect that these trees could have formed multiple rings in any given year, these trees provide two constraints: 1) the flood, if it were global, occurred more than 5,064 years ago, and 2) the Earth’s surface, where the trees were growing, has been identical to modern day over the last 5,000 years. The latter point is important, because flood geologists must assume that catastrophic geological processes continued for centuries after the flood to explain Quaternary deposits and erosional features like Grand Canyon or the Channeled Scablands.

  3. Long-term records of glacial ice can be dated by counting annual layers beyond 10,000 years. These annual layers can be recognized not only by appearance, but variations in chemistry, which removes any assumptions about growth rate during these intervals and precludes the possibility that multiple rings formed each year.
  4. Varved sediments with more than 10,000 layers, such as Lake Sugietsu, Lake Van, and the Cariaco Basin, to name a few. Geologists don’t just assume that these layers are annual, but must demonstrate rigorously that each layer exhibits some kind of seasonal signal (characteristic isotopes, organic matter, or mineral content).
  5. From Figure 4 in Reimer et al. (2013): example of radiocarbon calibration, plotting the radiocarbon age of samples against their known age (between 34–45 ka).

    From Figure 4 in Reimer et al. (2013): example of radiocarbon calibration, plotting the radiocarbon age of samples against their known age (between 34–45 ka).

    Radiocarbon calibration curves confirm that annual layers in trees and varved sediments are indeed annual. The radiocarbon age of annual layers within these deposits are always within ~10% of the age predicted by layer counting, back to nearly 50,000 years. If these layers accumulated catastrophically, or if the radiocarbon method were fundamentally flawed, we should not expect such a match. Additionally, since YEC’s suppose that radiocarbon ages are only apparently old (due to low 14C concentrations during and after the Flood), every marine, tree-ring, and varved lake chronology must be compressed down to ~4,000 years. In other words, the YEC paradigm would predict that trees, glaciers, corals, and seasonally active lakes regularly form 4-10 ‘annual’ bands every year. But they don’t.

  6. There is no radiocarbon in old samples, despite claims to the contrary. Geologically old samples of coal, diamonds, and graphite, for example, yield finite radiocarbon ages that are consistent with the expected level of contamination invariably introduced during sample collection and preparation.
  7. Continuous coral chronologies from modern communities (i.e. not buried in sediments) extend throughout the Holocene. Corals contain annual bands and may be combined like tree rings to construct long-term chronologies, or dated by the radiocarbon and/or U-Th method. Applying these tools, geologists use corals to reconstruct sea level over the last few tens of thousands of years (or more!).
  8. stalagmiteTauriusCave

    Cross section of a stalagmite prepared for stable-isotope analysis. Drill pits are from powders collected for U-Th dating. Image from UT-Austin media release.

    Secondary cave formations, such as stalagmites, can form relatively quickly (1–2 mm/yr) in tropical climates or where summer monsoons bring large volumes of precipitation to the cave system. For caves found in temperate or arid climates, however, the growth rate of stalagmites can be incredibly slow (<0.1 mm/yr). Advanced techniques in U-Th disequilibrium dating confirm what geologists long suspected: these iconic formations took tens of thousands of years to reach heights of half a meter or more.

  9. Large subterranean caverns do not form overnight, especially outside of tropical climates. The dissolution of caves is a rather slow process, due to the limited solubility of calcite in very slightly acidic rainwater. Although the process can be accelerated in the presence of active soils or even hydrogen sulfide (a microbial byproduct of petroleum degradation), the sheer size of natural monuments like Mammoth Cave and Carlsbad Caverns cannot be explained in a young-Earth timeline, especially given that these caves are lavishly decorated by secondary formations, which themselves take thousands of years to form.
  10. Large terrestrial lakes and inland seas have accumulated more than 10,000 years worth of deposition. Examples include the Black Sea, Dead Sea, Caspian Sea, Lake Baikal, Great Salt Lake, Lake Van, Lake Ammersee, Lake Sugietsu, and Lake El’gygytgyn, to name a few. These lakes are dated by combinations of radiocarbon, annual band counts, and isotopic records that correspond to climatic trends from ice cores. Some contain evaporite layers, indicating that the lakes dried up in the past. In the cases of Dead Sea and Great Salt Lake, this happened many times in the past on glacial-interglacial scales.
  11. Lake Baikal in Siberia has collected sediments that are inconsistent with any catastrophic inflow from the surrounding region. The sediments at the lake bottom are rather fine-grained, free of terrestrial plant debris (aside from microscopic pollen near the shoreline), and contain abundant diatoms. These diatoms flourish in the summer months but settle very slowly to the lake bottom, so their presence throughout the sediment column confirms that sediments accumulated under normal conditions, similar to today. Therefore, we can confidently say that the lake basin is potentially millions of years old, given the sheer thickness of lake-bottom sediments.
  12. Well developed river flood plains span large areas of temperate and tropical regions of Earth. These flood plains develop over long intervals of time as periodic flooding and migration of the river channel slowly erode the bedrock down to a flat surface. Attempts to describe vast planation surfaces by the retreat of flood waters do not work, because during floods, erosion is localized in channels that form along ‘weak points’ in the underlying rock and sediment. If this erosion took place soon after the Flood, the sediment would still be soft, exacerbating the localization of erosion in deep channels.
  13. Slithering stone in Death Valley. Photo by Momatiuk - Eastcott/Corbis photography.

    Slithering stone in Death Valley. Photo by Momatiuk – Eastcott/Corbis photography.

    Painfully slow erosional processes in modern deserts, involving wind, ground tremors, or even ice, are the best explanation for some rather bizarre boulders scattered across the dunes. Slow tumbling boulders in South American deserts, for example, had to be weathered slowly by wind in the arid highlands, and cosmogenic dating confirms their old age. Slithering stones of Death Valley, on the other hand, were proven to move only by seasonal ice. These findings imply that the modern landscape has changed little in thousands of years (if not millions!).

  14. Evidence for numerous glacial cycles during the Quaternary (i.e. the past 2.6 million years) is particularly abundant in the northern hemispheric continents of North America and Eurasia. These evidences include glacial tills and terminal moraines, which are buried within layers of Quaternary aged sediments. Between these glacially derived layers, relatively warm-weather plants populate the sediments of old river valleys, indicating that climate rebounded after each ice age to one similar to what we find today.
  15. Quaternary deposits and landscapes are far too complicated to have accumulated in the ~4,500 years following the Flood. Everywhere we look on Earth, we truly find evidence for ~2 million years worth of processes, whether at high latitudes (where we find evidence for repeated glaciations and deglaciations, separated by warm intervals) or in the tropics (where we find thick desert dune sequences alternating with humid intervals) or in the oceans (where 2 million+ years of Milankovitch cycles are recorded in only a few meters of silt and clay) or in the high mountains (where alpine valleys have been carved out by rivers or glaciers, then infilled by coarse sediment, then eroded again, etc.). Flood geologists unanimously assert that the Quaternary period represents the ‘post-Flood’ era, but there is good reason that conventional geologists ascribe a much longer age: 2.6 million years.
  16. Glacial tills from ancient glaciations, such as the ‘Snowball Earth’ episodes in the Late Proterozoic
    Dropstones in a glacial diamictite from Death Valley, California.

    Dropstones in a glacial diamictite from Death Valley, California. Image credit.

    and cold intervals beginning the Late Ordovician and Late Pennsylvanian periods, are found within the geological record and so must be reinterpreted by Flood geologists as submarine deposits of boulders and mud during Noah’s flood. Though ancient tills do occasionally resemble submarine flows, ancient glaciations are not inferred by these sedimentary deposits alone. Instead, a suite of geological data, from fossils to paleoceanographic data to rock chemistry, all support the idea that the whole Earth was much cooler when these tills were deposited.

  17. Continental ice sheets do not form in a matter of centuries, especially those that were more than a mile thick and extended in some cases to southern Siberia and the central Great Plains, USA. Flood geologists must maintain, however, that massive ice sheets nearly half the size of Russia not only grew, but melted entirely, then regrew, melted entirely, and regrew more than a dozen times in less than 200-700 years (the timeline depends on which YEC you ask!).
  18. Human occupations of nearly every continent can be demonstrated beyond 10,000 years, e.g. in South Africa, ruling out the possibility that humans repopulated the Earth after being obliterated only ~4,500 years ago.
  19. Ötzi the Iceman has frequently made headlines in creationist writings, because they accurately perceive this unique find as a challenge to the young-Earth timeline. The remains of this murdered Alpine farmer date to ~5,300 years old, which YEC’s arbitrarily dismiss as “inflated”. Regardless, they do admit that he lived sometime in the beginnings of human civilization (i.e. very soon after the Flood), and so they attempt to turn the argument on ‘evolutionists’ by emphasizing the level of technology (tools, agriculture) carried by Ötzi and his village—”How can this ‘primitive’ man be so advanced?” This response is a non sequitur, because the artifacts found with Ötzi are entirely compatible with reconstructed histories of European peoples. What YEC’s overlook is the geological context of the body: it was preserved in undisturbed ice near the top of a mountain range. This tells us that the morphology of the Alps has changed very littlesinceÖtzi was alive. So when did theAlpshave a chance to shed the kilometers of sediment that once covered their peaks? ThemountainsinwhichÖtzi wasfoundare indeed very ancient, far older than the body of this 5,300-year-old village outcast.

    Ötzi the Iceman, trapped in ice ~5,300 years before present and nearly perfectly preserved (stomach contents and all!).

  20. Human settlements that are now submerged due to sea-level rise have been documented beneath the English Channel, North and Baltic seas, off the coast of Israel, Florida, and beneath the Black Sea, to name a few. For much of human history, global sea level was up to ~130 meters lower than today, exposing far more of the continental shelves and pushing ancient coastlines far away from their modern locations. This allowed for human settlements to develop in sites that are now completely submerged. Following the ice age, however, sea level rose sharply and reached near modern levels at ~8,000 years ago. Whatever the absolute timeline, the young-Earth view allows too little time for human populations to develop, migrate across the globe, and construct large settlements prior to the sea-level rise following the ice age (which they assert happened only a few centuries after Noah’s flood).
  21. Fossils record long histories of migration of animals from Eurasia to the “New World”, which cannot be accounted for in the young-Earth timeline. Large mammals such as mammoth, mastodon, and giant sloth reproduce far too slowly to account for the population sizes indicated by fossil graveyards between Siberia and the Americas.
  22. There is no record of migration from Central Asia to Australia for many species unique to the land down under. Their ancestors, however, are found in the fossil record and imply that modern populations derived from species that arrived to the island well in the distant past, not after the Flood only ~4,000 years ago.
  23. Modern oceans are too salty to have been formed only ~6,000 years ago. We know this salt was delivered slowly to the oceans mainly via rivers (i.e. as opposed to being created in situ), because the relative abundance of salts in the ocean is related to their relative solubilities and abundance in the Earth’s surface.
  24. Cenozoic aged marine sediments in the Gulf of Mexico or along the west African and east South American coastlines, for example, are far too thick to be explained by ‘post-Flood’ processes. This fact has caused some YEC’s, such as Michael Oard, to push the ‘post-Flood’ boundary later and later into the Cenozoic and consider these marine sediments as Flood deposits. However, the structure of marine sediments in the Gulf of Mexico and the equatorial Atlantic is clearly related to the modern topography, where large rivers like the Mississippi, Amazon, Congo, and Cross have dumped tons of sediment into the seas, causing massive deltas to form over long periods of time. Due to the economic reward for exploring these sites (which contain abundant oil), geologists have thoroughly mapped out the evolution of ancient deltas through miles of sediment. Their result ubiquitously inform us that the modern landscape is very old and rather stable, and that these late Cenozoic marine sediments were not deposited through catastrophic processes, but by everyday rivers at rates observed today.
  25. Deep ocean sediments take far too long to settle to have accumulated in less than 5,000 years. Today, the entire seafloor is covered with microscopic species of plankton, diatoms, radiolaria, etc., in addition to tiny bits of clay and calcite. These particles are so small, that they would remain in suspension under flowing water, so their presence on the seafloor must be explained by a long-time in which they could settle through miles of seawater. The history of seafloor sediments is further amplified by the fact that marine tephra (volcanic ash layers) occur throughout marine cores around the world, but volcanic ash also needs time and calm water to settle out.
  26. santorinideposit

    A 3,500-year-old volcanic ash deposit from Santorini volcano, in three stages: an air fall pumice (bottom), followed by laminated ash that formed underwater (middle tan layer), covered by a pyroclastic flow (top white layer). Photo by Lee Siebert found here with full description.

    Volcanic ash beds (sedimentary tuff), frequently used to date sedimentary rock layers, were mainly deposited in dry conditions. Geologists can distinguish between ash layers that settled in ocean basins (marine tephra) and those that fell over dry land (air fall deposits). When volcanic ash is deposited in flowing water, it produces yet different features identifiable in outcrops, such as grain sorting and lamination. Therefore, not a few volcanic ashes in sedimentary strata contradict the Flood geology scenario, especially because these ash falls take time to accumulate from the air and harden to the point that water-lain sediments can be deposited on top without compromising the structure of the soft ash.

  27. The geologic column is no remnant of an ancient flood deposit, global or not. Fine details, in the form of thin layers of alternating clay and limestone, or irregular sand deposits that resemble modern river channels, defy catastrophic explanation, which explains why catastrophism has long been abandoned by research geologists.
  28. There are simply too many sediments buried in the crust to be explained in a young Earth. Contrary to the claims of Andrew Snelling, the ocean floor contains about as much sediment as we might expect after ~160 million years. In addition to ocean sediments still underwater, however, YEC’s must also explain the origin of the trillions of trillions of tons of limestone, sandstone, and mudstone now buried on the continents. These sediments, comprised of broken down minerals, must have originally weathered from igneous or metamorphic material, after which it was sorted by size through surface processes (like rivers, winds, and gravity). But this is not a rapid process, inviting the question: even if a global flood could have buried this much sediment (it can’t), what is the origin of the sediment in the first place?
  29. The distribution of sedimentary rocks is weighted too heavily over the continents, which is the opposite of what we’d expect in a global flood. Floods move sediments from high elevation to low elevation, depositing them in sedimentary basins. During the Flood, the oceans would have constituted the largest and deepest basins, but most sediments remainedonelevated continents. How did this happen? Did the laws of physics stop working?


    The “Great Unconformity” in Grand Canyon. Photo by Marli Miller.

  30. Angular unconformities became one of the principal evidences against catastrophism in the 19th century, and for good reason. For an angular unconformity to develop, a sequence of sedimentary layers must be deposited horizontally, then tilted or folded above horizontal, then eroded along a flat (or nearly flat) surface, after which new layers are deposited horizontally on top of the erosional surface. We can explain all these steps through modern geological processes. Flood geologists, on the other hand, must explain 1) how these horizontal strata became angled amid the flood, 2) had time to erode to relatively flat surfaces, and 3) why we do not find deep canyons associated with unconformity surfaces, since deep, rapid flowing water would tend to carve into the unconsolidated sediment.
  31. This buried landscape, for which little explanation is needed, absolutely defies Flood geology. It is rather a testament to deep time, in which an ancient river valley cut its way though thick sequences of sedimentary rock, only to be buried suddenly and preserved in subtle disconformities between the overlying layers. But these disconformities make for excellent acoustic reflectors, and so the ancient landscape is visible through seismic imaging—a way of treating the Earth to a million-dollar ultrasound.buriedlandscape
  32. Sedimentary features in limestone are similar to those forming today in shallow marine environments. Everything from ooids (tiny spheres that build up like snowballs under wave action) to cross bedding to mudcracks to karst dissolution in ancient limestones falsifies the young-Earth timeline, because these limestone formations were deposited in calm, shallow seas—not a deep, worldwide flood.
  33. Exposure surfaces in limestone are recognizable through features like mudcracks, hardgrounds, and karst dissolution. Karst erosion takes place when relatively acidic waters (like fresh rainfall) dissolve cavities in exposed layers of hardened lime mud. Since karstic surfaces are found throughout the geologic column (including in the Redwall Limestone of Grand Canyon), we can rule out the possibility that limestone layers accumulated under a global flood.
  34. Carbonate rocks (limestone and dolostone) comprise more than 20% of all sedimentary rocks, but Flood geologists cannot explain extensive formations of dolostone—(Mg,Ca)CO3—which forms only under unique conditions not seen today in the oceans. To avoid the problem, they speculate that enhanced delivery of magnesium to the ocean (via deep-ocean vents, or the “fountains of the deep”) would havedriventhe formationofdolostone during the Flood. But in fact, dolomite does not form under these conditions, and so the Flood geology model predicts rather that mostcarbonatesshouldbecomprised of aragonite, the high-magnesium variant of calcite. Every piece of dolomite in the geologic record is firm evidence against the Flood model.

    Areal extent of some major evaporite deposits. Image from Paleobabbler.

  35. Flood geology cannot explain the size and presence of massive evaporite deposits in basins like the Gulf of Mexico or the Mediterranean Sea (a small sampling of the world’s sedimentary salt). Halite (NaCl; same as the salt on your food) is extremely soluble in water, especially at higher temperatures. Therefore, Flood waters would have had to evaporate within individual basins until <10% of the original water mass remained (meaning millions of cubic kilometers were evaporated!). Again, this would imply that the ground was exposed at numerous points during the Flood (contrary to scripture). But it also requires that extreme evaporation could persist over significant intervals of the Flood (during which no water flooded the basins?), which is not physically possible. Evaporation stops when relative humidity in the atmosphere reaches ~100%, but the more water is evaporated, the greater the relative humidity becomes. At 100%, the humidity returns to the ocean as rain. Thus the hydrological cycle would have prevented any large basin from evaporating enough water to deposit halite over its base.
  36. The size and thickness of chalk deposits has frequently been cited as solid evidence against the flood. Young-Earth geologists (esp. Andrew Snelling) have responded by offering pseudo-scientific calculations that supposedly account for the global mass of chalk. These calculations are scientifically meaningless, however, because 1) they assume that coccolithophores (which form chalk in the surface ocean) sustained unreasonably high productivity rates over a significant portion of years leading up to the Flood, 2) that the “fountains of the deep” provided nutrients to the surface ocean (instead of poisoning them, as discussed above), and 3) that all chalk produced prior to and during the Flood could have settled in a coherent deposit at the bottom of the sea (rather than remaining in suspension and mixing with other particles in the surface ocean—a more likely scenario if the Flood was accompanied by strong currents).
  37. Syntectonic deposits are abundant throughout the sedimentary record. As the name implies, syntectonic deposits form simultaneously with tectonic deformation of the local geology. If you’ve ever seen an alluvial fan collecting sediments from the side of a mountain, especially near a large fault, then you can visualize the painfully slow process in action. As the mountainside is exposed little by little, due to adjacent valley dropping in elevation every time an earthquake hits, pebbles and boulders are episodically washed into the valley. Because syntectonic deposits contain eroded pebbles and boulders of underlying sedimentary rocks, their presence in the geologic column makes no sense within a ‘Flood geology’ interpretation. Those underlying sediments must have been solid before they could be broken off and polished into smooth boulders found inmostsyntectonic layers.

    Syntectonic deposits in Echo Canyon Utah. Original photo by Matt Kuchta.

  38. Large extensional basins, such as Death Valley and the Great Basin in the US, contain thousands of meters of coarse sediments that were eroded from the adjacent ranges. These basins only deepen when infrequent, large earthquakes cause the valley to drop 1–2 meters at a time. Even if we allow that earthquakes were more frequent in the past, there is a limit to how fast semi-arid valleys can collect millions of tons of boulders in their center, because major flooding events are required to move these sediments several miles over a shallow slope.
  39. The total offset in large transform faults, such as the San Andreas fault, points to a very long history of slow deformation. Since its inception, the San Andreas fault has separated sedimentary deposits that appear on both sides by 150 miles, but the average slip rate today is only ~5 cm/yr. One could argue that the rate was higher in the past, but there is no direct evidence for this, and large episodic earthquakes can shift the fault blocks locally by only a few meters. On the other hand, there is evidence from the offset of modern gullies and streams that movement has been just as slow in the past.

    Offset of a small creek along the San Andreas fault. Image from Zielke et al. (2012).

    Offset of a small creek along the San Andreas fault. Image from Zielke et al. (2012).

  40. Radiometric dating confirms that modern slip rates of tectonic plates, as estimated by GPS data, remained relatively constant over millions of years. The ability to predict radiometric dates by uniformitarian ‘assumptions’ strongly corroborates plate tectonic theory and removes the assumption of uniformity of process.
  41. The abundance of oil in sedimentary rocks completely contradicts the young-Earth timeline, because oil cannot form within ~5,000 years at temperatures less than ~300°C—far greater than is found in every oil and gas field today. At best, the young-Earth scenario might predict sparse fields of natural gas, being produced by decaying organic matter, but instead we find hundreds of reservoirs containing billions of barrels of oil.
  42. There is too much organic matter in Earth’s crust to have been buried in a single flood event. Flood geologists must contend that most (if not all) of this organic matter—called the biomass—was alive or only recently deadjustprior to the flood. Coal and oil reserves are the most obvious examples of ancient biomass, but nearly every sedimentaryrockcontains a little (up to 1%) by weight. When allsourcesare taken into account, we find that the biomass buried in Earth’s crust is 3,000 times larger than what is found today—far more than could have been present on Earth at any given time.

    Early Cretaceous plant fossil in coal. Photo from Wikipedia commons.

    Early Cretaceous plant fossil in coal. Photo from Wikipedia commons.

  43. Coal beds defy rapid deposition, because the high concentration of organic matter begins with the slow accumulation of plant material in oxygen-poor swamps (and not by rapid burial of floating forests). The occasional preservation of leaves and woody material in coal seams would not be possible if all the buried plant material were fresh to begin with (as with rapid burial of existing forests), but requires that organic remains be at varying stages of decomposition.
  44. Coalification (turning plant matter into high-grade coal) is a slow process, which cannot be compressed to the young-Earth timeline. Experimental attempts to make artificial coal (cited by Snelling here) have only produced very low-grade lignite and coalified wood. Furthermore, these experimental setups (which do require high pressure/temperature and up to several months) rarely reflect natural settings and have yet to produce coal that closely resembles natural samples.
  45. If the majority of the Earth’s sedimentary rocks were deposited within a single flood, then those sediments should all be at approximately the same temperature today, and that temperature should be similar to the average water temperature during the Flood. It would take millions of years for a smooth temperature gradient to form (cool at the surface, hotter nearer the mantle), which is what we find today in deep wells.
  46. Remnants of soft tissue are extreme rarities in sediments older than Quaternary, possibly preserved in a handful of samples around the globe. Paleontologists continue to debate, for example, whether soft tissue in dinosaur bones derived from actual dinosaurs or microbial biofilms. But whatever the answer, we can all be confident that soft tissues are not regularly recoverable from Paleozoic and Mesozoic fossils. If these organisms were buried less than 5,000 years ago, however, soft tissues should be the rule, not the exception. According to the YEC timeline, mammoths and other megafauna died only years to centuries after the dinosaurs, yet we find hair, collagen, and even DNA in these animals all the time. So why not in dinosaurs and trilobites?
  47. Contrary to what we might expect from a Flood geology scenario, deep reservoirs of groundwater are not remnants of ancient oceans, but were accumulated by infiltrating rain and snow. Whenever oil companies drill deep into sediments, they always encounter very salty water (called connate water), whichhasto be pumped before oil is accessible. It was originally thoughtthatthe salinity of these waters derived from the oceans in which thesedimentswere deposited, but their chemical and stable-isotope signatures contradicted this hypothesis. Flood geology has no room in its
    Polystrate tree fossil. Note the base of the stump is rooted in a more organic-rich deposit, while the top of the tree is truncated sharply. Photo from Wikipedia commons.

    Polystrate tree fossil. Note the base of the stump is rooted in a more organic-rich deposit, while the top of the tree is truncated sharply. Photo from Wikipedia commons.

    timeline for sedimentary rocks to have been ‘flushed out’ by infiltrating precipitation, because deposition would have to occur too rapidly. If the geologic column were deposited in a global flood, therefore, we should expect the groundwater trapped in deep sedimentary layers to be the very ocean water that once covered the Earth.

  48. Contrary to YEC claims, polystrate fossils are better interpreted by conventional geology and contradict the Flood geology paradigm. Most polystrate trees are rooted in organic-rich layers such as coal seams or paleosol beds. In other words, the trees were growing in place when covered abruptly by rising floodwaters, and were not uprooted and transported long distances. This means that after the formation of the coal/paleosol, there had to be time for a forest of trees to grow several meters, after which a large flood (not global, just the kind that would engage our National Guard today) buried whole stumps up to a couple meters with sand and mud. In all occurrences of polystrate trees, the tops of the trees are missing (truncated), having rotted off after they were exposed above the sediments for a long time.
  49. Fossilized burrows and marine trackways reflect everyday conditions in ancient ecosystems, where worms, trilobites, or molluscs dug calmly through soft mud on the seafloor in search of food. The claim that paleontologists have unanimously mistaken these trackways for escape efforts during a catastrophic flood is not only presumptuous, but it ignores the bulk evidence.

    Trilobite trackway in Cambrian sandstone. Image from PaleoSearch.

  50. Mudcracks are common features in layers of sand, silt, and clay that are interpreted to have formed in floodplains or shallow lakes and tidal flats. Despite decades of being aware of the problem, Flood geologists have not satisfactorily been able to explain why mudcracks cover thousands of individual layers throughout the rock record. These features do not form under water, but require an exposed, drying surface of semi-cohesive sediment.
  51. Ripples readily form in sandstone under flowing water, but not at speeds required by the Flood. Therefore, the common preservation of small ripples cannot be reconciled with the Flood model, but rather tells us that the sand must have been buried in calm seas with gentle waves.
  52. Raindrops on the surface of sedimentary layers—these are relatively self-explanatory. If we take Genesis as our guide, sedimentary layers could not be exposed during the course of the Flood, and so we should never expect to find raindrops imprinting their surface. Even if we do allow forthisunbiblical possibility, however, raindrops imprints cannot be preserved if they are swiftly covered by a new layer of sediment. For raindrops to become ‘fossilized’, theimprintmust be made in a semi-cohesive layer (i.e. one that is not saturated with water, but not completely hard), which needs time to
    A 15-million-year old piece of poop, called a coprolite. Image credit.

    A 15-million-year old piece of poop, called a coprolite. Image credit.

    harden slightly in the absence of flowing water before another layer is deposited on top. Raindrops in sediments contradict flood geology outright.

  53. Fossilized poop, called coprolite, is found throughout the fossil record alongside the animals that produced them. These paleontological oddities are indicative of normal ecological conditions and contradict any scenario in which the ‘poopers’ were catastrophically buried.
  54. The nature of the fossil record contradicts the expectation of ‘rapid burial’ for most land-dwelling organisms. By and large, terrestrial fossils are the weathered remains of animals, which were long exposed to the elements before disarticulating and washing into a river channel, lake, or floodplain. Vertebrate skeletons are almost never found intact, and more weather-resistant pieces (like tooth enamel) are preferentially preserved, suggesting that rapid (live) burial was an extreme rarity in geologic history.
  55. Fine sorting of marine microfossils is inconsistent with the Flood scenario, because specimens of foraminifera, radiolarians, and coccolithophores are approximately the same size. Therefore, these tiny shells should be scattered stochastically throughout the sedimentary record, if they were subject to the same hydrodynamic forces of a single global flood. Instead, individual species are commonly confined to narrow zones in the fossil record and used as index fossils for dating layers of marine sediments.
  56. Cast replica of footprints made by a mammal-like reptile in the Coconino Sandstone near Ash Fork, Arizona. Photo credit: PaleoScene.

    Fossilized tracks in eolian (desert dune) deposits, such as the Coconino and Navajo sandstones, are inconsistent with the young-Earth proposition that these sediments accumulated under water. Extremely high sustained flow rates (>2 m/s) of very deep waters (up to 100 m or more) are required to form dunes of comparable size to those in the Coconino and Navajo sandstones. At these flow rates, it would be impossible for any submerged animals (especially small reptiles) even to make contact with the sediment surface, let alone for any prints to be preserved.

  57. The occurrence of widespread, eolian sandstone formations negates any model that cites a worldwide flood to explain their deposition. Of course, Flood geologists attempt to argue that eolian sandstones must have been laid down by water (more than 100 meters deep, flowing more than 2 m/s), but ignore the preponderance of evidence, which is more consistent with dry dune deposition.
  58. Paleosols are sedimentary layers that show evidence of soil formation by plants and microorganisms. Typically they can be recognized by distinct mineral compositions or chemical signatures, but direct reworking of sediment through biological agents may also be observed (for example, in situ roots and carbonate nodules). Not all paleosols show the same degree of soil development, but all are indicative of a long-lasting stable surface. YEC’s are forced to reinterpret paleosols as artifacts of chemical modification after rapid burial during the Flood, but geologists have become acutely aware of how to distinguish between these processes and true soil horizons.
  59. Animal tracks in general are evidence of an exposed surface, on which sediments were somewhat coherent (i.e. not too soft, not too hard; imagine trying to preserve your own handprint in cement). Nonetheless, YEC’s have deemed trackways consistent with their paradigm, because they insist that the floodwaters receded and covered the land numerous times. Besides the fact that Genesis 8 tells us the surface was not exposed until very late in the flood (and so their model contradicts scripture), it is very unlikely that any tracks could be preserved in those conditions. Once the floodwaters returned, they would tend toward erosional processes (removal of the entire surface layer, tracks included). The Flood model firmly predicts the absence of trackways in the sedimentary record, but in fact they are abundant.
  60. Fossilized nests, e.g. from dinosaurs, are indicative of stable, everyday ecosystems, and not catastrophic flooding of the continents. Both nests and eggs are fragile, which explains their rarity in the rock record. But abrupt burial in a high-energy flood cannot possibly explain their occasional preservation.
  61. The Grand Canyon was eroded and widened slowly by annual precipitation, as evidenced by the fact that the North Rim lies further from the main course of the Colorado River. A very gentle slope causes more runoff to enter the canyon from the north side, which, as Wayne Ranney (2012) explains, allows “for more erosion in the side streams on the north side of the river. For this reason, the North Rim is eroded away from the river about twice as far as the South Rim.”
  62. The Grand Canyon itself is only deepened episodically during extremely high floods, which do not regularly occur in the modern climate of northern Arizona. Therefore, it must have taken numerous glacial cycles, during which the jet streams migrate southward and bring more rain/snow to the American southwest, to account for the great depth of the canyon today.
  63. The walls of the Grand Canyon contain numerous caves with speleothems, implying that the water table once stood high above its present position for extended periods of time. Catastrophic carving of the Grand Canyon cannot possibly explain these features, because it allows no time for caves to form and no mechanism by which they could be decorated with stalagmites and stalactites.
  64. Figure 1 from Noffke and Awramik (2013). Modern and ancient examples of stromatolites and microbially laminated structures.

    Figure 1 from Noffke and Awramik (2013). Modern and ancient examples of stromatolites and microbially laminated structures.

    Stromatolites and thrombolites are fine-laminated mounds built by algae and other microorganisms. These features not only take long periods of time to form, but their occurrence in repeated sedimentary layers argues strongly against catastrophic burial. They do not appear randomly in the geologic column, but are always positioned upright (in situ growth position) over wide areas within single layers of limestone—precisely what we’d expect if they grew in ancient oceans that slowly amassed limestone mud. Finally, these laminated mounds are frequently surrounded by fragmented shells of shallow-marine organisms typical of the same environment.

  65. Consistent patterns in magnetic reversals recorded on the seafloor strongly support the conventional model of plate tectonics, in which slowly forming oceanic basalts record the dominant magnetic signature at the time they were formed. YEC’s contend that these magnetic reversals occurred rapidly during the flood, but this proposal is easily falsified. If the entire Atlantic and Pacific basins formed during and/or shortly after the Flood, then Earth’s polarity would have reversed multiple times before oceanic basalts even had a chance to cool and preserve the signature! Flood geology thus predicts that either a single polarity signature should persist across ocean basins or the signature should be stochastic, with no striped pattern.
  66. Magnetic reversals recorded on the seafloor correlate to magnetic patterns in land sediments (e.g. Heller and Tung-Sheng, 1982; Cunningham et al., 1994; Ding et al., 1999), vastly improving the dating of continental deposits that lack datable layers of volcanic ash. Where ash layers do exist, they allow for independent dating of magnetic reversals on land by the Ar-Ar method. This independent corroboration of dates improves the strength of magnetic ‘stripes’ on the ocean floor as evidence for an ancient Earth.
  67. Earth’s magnetic field is not decaying exponentially, but has varied much less over the past 7–9,000 years (e.g. Korte et al., 2011; Nilsson et al., 2014). Magnetic field strength was weaker, not exponentially stronger, for much of this interval. Attempts to suggest that the Earth cannot be older than 10,000 years due to an exponential decay of Earth’s magneticfieldare based on a blind extrapolation of historical measurements (which span no more than 150 years) into the past. This approachignoresthe abundance of paleomagnetic data from human artifacts, sediments, and recent lava flows.


    Figure 6c-d from Nilsson et al., 2014. Modeled history of the dipole moment of Earth’s magnetic field over the past 9,000 years, based on magnetic field intensities recorded by archaeological and geological samples.

  68. The entire field of chemostratigraphy makes no sense within Flood geology. First, the stratigraphic shifts in chemistry—meaning, as we analyze rock chemistry from the bottom of the geologic column to the top—are too large to have occurred during a single year. This is true particularly of isotopes of carbon, sulfur, and strontium, because the amount of these elements dissolved in the ocean is too large to be greatly affected within a short period of time. It would be like trying to change the water color of a swimming pool by dumping in a few cups of coffee!
  69. Event stratigraphy, which utilizes abrupt shifts in rock chemistry as time markers, helps geologists to correlate sedimentary rocks from very different parts of the world. When we examine sequences of sedimentary rocks that are rich in fossils, the order and timing of chemical events just happens to correspond to the order and timing of fossil events (e.g. the disappearance or first appearance of certain fossil species). This correspondence is not possible in the flood geology model, however, since the ordering of fossils in various parts of the world could not have been a matter of timing (i.e. it couldn’t depend on which day of the Flood they were buried).
  70. The mere existence of isotopes is not predicted by the young-Earth paradigm, but makes sense only in conventional astrophysics. Nearly all elements of the periodic table exist in various isotopes, due to their being formed in the process of stellar evolution. As stars grow larger, heavier elements are produced through nuclear synthesis. Outside of this mechanism, we should not expect isotopes to be a common feature in basic chemistry.
  71. Short-lived isotopes are detectable only from distant supernovas. These are unstable elements that decay relatively rapidly after formation and so should be absent in a 4.5-billion-year Earth. This discrepancy provides unambiguous support for the conventional age of our solar system and models of stellar evolution.
  72. Radiometric dating of chondritic meteorites is consistent between methods and yields ages of 4.56 billion years for our solar system. It is currently inconceivable how this date could be wrong by a factor of 1 million.
  73. Potassium-argon dating is well known for its potential problems, but still provides one of the best methods for dating ancient volcanic flows. Even when excess argon is originally present, as is evident in the dating of certain historical eruptions, the date is only apparently too old by a few million years at most. Therefore, K-Ar dates in excess of tens or hundreds of millions of years tell us clearly that the Earth is not young, because otherwise, we could not explain such high concentrations of argon in these volcanic rocks.
  74. The Argon-Argon technique removes most uncertainties about the original presence of excess argon in samples, confirming that K-Ar dates are both real and generally accurate. Corroboration of Ar-Ar dates by other methods—e.g. when applied to the Cardenas Basalts of the Grand Canyon—further improves our confidence in the respective techniques.
  75. Uranium-Lead dating techniques consider the decay of multiple isotopes (238U, 235U, and 232Th) into stable forms of lead. If the respective half-lives of these elements changed significantly in the past, then the technique simply wouldn’t work, because each half-life is vastly different. Accelerated nuclear decay, in other words, would result in massive discordance between age estimates from each decay chain. However, the U-Th-Pb method, especially when applied to pristine zircons, provides one of the most precise geochronometers for the bulk of Earth history.
  76. Flood geologists cannot account for the abundance of 230Th in secondary calcite deposits, such as speleothems, carbonate lake sediments, and corals. Since thorium is not soluble in oxidized water, these formations originally contained none. Therefore, present concentrations can only be accounted for by radioactive decay of 234U into 230Th, which has a half-life of 245,000 years. If modern corals, lakes, and cave deposits formed only after a global flood, some 5,000 years ago, then none should yield dates older than this.
  77. Cosmogenic dating utilizes short-lived isotopes that are created in situ by incoming solar radiation or high-energy particles from space. When rocks are exposed to the atmosphere, such as large boulders on the side of a mountain, they accumulate short-lived isotopes. When rocks and minerals are hidden, through burial under sediments or ice, short-lived isotopes decay at a known rate. Through a variety of methods, geologists have used cosmogenic dating methods to constrain the buildup and retreat of large ice sheets, development of alluvial fans, river plains, deserts, and other surface features across Earth. Of course, these dates invariably suggest that the most recent deposits on Earth are not less than 10,000 years.
  78. There is too much helium in zircons, contrary to what Russell Humphreys has conjectured in his unscientific analysis. Geologists regularly use the amount of helium in certain minerals to constrain rates of tectonic uplift, because it accumulates at a known rate (dependingonthe concentration of Uranium/Thorium), so long as the mineral stays below a threshold temperature. This method (U-Th-Hethermochronology) regularly yields ages of tens of millions of years, which is to say that many millions ofyearswere required to account for modern concentrations of helium.


    Cartoon illustration to explain formation of a particular type of ophilolite. From Rolland et al. (2010).

  79. Ophiolites are remnants of ancient oceanic crust, which have been thrust onto the continent. Geologists were originally confused by the large bodies of ultramafic (super rich in Fe and Mg) rocks on land. But by studying the chemistry and mineral composition of ophiolites, geologists recognized their oceanic origin and could identify the processes responsible for their formation. As it turns out, most ophiolites were formed near subduction zones (e.g. like we find around the Phillipines), and not in mid-ocean ridges. We know this because subduction of ocean sediments and crust influences the chemistry of newly formed lavas in a very specific way. And so, ophiolites tell a much longer story than the YEC could allow, in which 1) ancient (pre-Flood?) oceanic crust began to buckle until one plate subducted beneath another, 2) forming an island chain like Japan, which 3) began to stretch away from the continent, 4) allowing new oceanic crust to form, until 5) the entire suite was crumpled up as the island chain collided with the main continent, 6) ultimately preserving portions of the ocean crust and overlying sediments on land. Each of these steps requires more than a few thousand years.
  80. Cosmogenic beryllium (10Be) is present in volcanic emissions above young subduction zones, but absent in older ocean sediments. This radioactive isotope is formed continuously in the atmosphere, much like radiocarbon, but has a much longer half life. It is useful in dating certain marine cores, since the concentration of 10Be decreases with depth—as expected if the ocean sediments accumulated over millions of years. The fact that 10Be is present in younger subduction zones, such as the Lesser Antilles, indicates that ocean sediments were subducted and then recycled back into recent volcanic flows within a few million years. Since 10Be is absent, however, from the majority of volcanic emissions and from ocean sediments that are older than Pliocene in age, we can be confident in their conventional ages (>5 million years).
  81. Large igneous bodies take time to cool, such as those that comprise the core of the Sierra Nevadas, Andes, Rocky Mountains, and other large mountain belts around the world. Even in the presence of circulating waters, the sheer amount of heat originally present in magmatic intrusions requires hundreds of thousands to millions of years to dissipate, before the magma may crystallize completely into solid rock. This process is slowed significantly by overlying sediments, which act as insulators.
  82. Coarse-grained granite from the Town Mountain Granite.

    Coarse-grained granite from the Town Mountain Granite.

    Coarse grains in igneous intrusions confirm that they indeed cooled very slowly, and not by rapid dissipation of heat via water or any other process. Only slow cooling allows for large, distinct minerals to form (called phaneritic texture), as is common in granite and diorite. Whenever you find a rock that resembles the image to the right, you have met a witness against the young-Earth paradigm.

  83. The intrusive igneous rocks exposed today were formed at great depths, indicating that miles of solid rock had to be weathered and eroded in the past. Even under catastrophic conditions, this process alone could take tens of millions of years. Today, granite exposures such as in the iconic Yosemite Valley continue to uplift in response to the removal of the overlying rock.
  84. Volcanic sills, which are intruded between sedimentary strata, require that the layers be hardened first. Otherwise, these lava injections have no physical guide that would confine their shape to lateral sheets of basalt. It is the brittle break between solid sedimentary rocks that causes volcanic sills to parallel the direction of bedding. Where is there time in Flood geology for sediments to harden completely, then to fracture and allow injection to form a sill, and finally time for cooling of the lava itself into solid rock? Volcanic dykes similarly require brittle fractures in the rock layers to explain their shape.
  85. Volcanic island chains, such as Hawaii, elucidate the multimillion-year effects of plate tectonic theory. Migrating lithospheric plates (and/or ‘hot spots’) cause the center of volcanic activity to migrate in a roughly linear pattern, resulting in a long chain of individual islands (which themselves are large volcanoes). Radiometric dating of volcanoes, from recently active to long extinct, confirms the predicted rate of plate motion based on modern observed values.
  86. Even if one rejects these dates, we must still account for the sheer size of the subaqueous mountain belts, which form gradually by periodic eruptions. It takes time for one deposit to cool and solidify, before another can be laid on top. Otherwise, a 33,500-foot shield volcano could not form, but only a relatively flat plateau of flood basalts on the seafloor.
  87. Extent of the Siberian Traps. Image from Wikimedia Commons.

    Extent of the Siberian Traps (blue line). Documented lava deposits shown in red; tuff in purple. Image from Wikimedia Commons.

    Volcanoes would have destroyed all life on Earth, assuming that volcanic deposits now preserved in the geologic column had to have formed during a single year. Massive eruptions have been well preserved, for example, in the Deccan traps (Siberia) or in flood basalts of the Snake River basin (northwestern U.S.). Geologists have modeled the impact of these individual lava flows on terrestrial and ocean life, and consistently conclude that each could have contributed to dramatic climate change and major extinction events. But these models assume that lava of the Deccan traps, for example, erupted over hundreds of thousands of years. Cumulatively—and if we require that all eruptions took place during the Flood year—these volcanic flows would have poisoned the oceans with heavy metals and saturated the atmosphere with carbon dioxide and sulfur gases. The sheer amount of carbon dioxide would have driven the oceans toward acidic conditions too vile for any surface life.

  88. Carbon dioxide emissions from volcanic events would have driven atmospheric concentrations to ~50,000 ppm or more. That’s more than 1,000 times what we find today! There is no evidence, however, for the extreme heating of Earth’s surface that inevitably would have ensued (on the contrary, YEC’s believe an ice age followed the Flood). Additionally, not enough time has passed since the Flood for such high levels to have equilibrated to those observed prior to the modern industrial age. The mass of volcanic deposits within the geologic column precludes the Flood geology model entirely.
  89. Large metamorphic bodies do not form rapidly, but require hundreds of thousands to millions of years worth of circulating waters under intense heat and pressure. The notion that catastrophic plate tectonics can explain the metamorphism of extensive mountain belts has no basis in physical science.
  90. Large sphalerite (zinc sulfide) crystals forming in ore body. Image from MGG&MS.

    Large sphalerite (zinc sulfide) crystals forming in ore body. Image from MGG&MS.

    Gemstones and other rare minerals form by slow accumulation of rare elements in magma or in water circulating through rocks. The greater the size, purity, and quality of gemstones, the longer it would have taken to form them. Gemstones are thus a testament to the antiquity of the Earth.

  91. Radiogenic isotopes in rocks from the crust to the deep mantle indicate a long history of chemical evolution deep within the Earth. As large igneous bodies cooled at the surface to create continental and oceanic crusts, some elements preferentially were incorporated into solid minerals, while others remained preferentially in the liquid mass in the mantle. This chemical differentiation explains very well the difference in isotope ratios between the crust and deep mantle rocks, assuming that it occurred over several billion years. Young-Earth geologists, on the other hand, cannot explain the most basic geochemical features of the Earth’s crust and mantle.
  92. Catastrophic plate tectonics is the only way to explain the bulk evidence for plate tectonic theory in a young-Earth timeline. But two major problems arise: excess heat and lack of a viable mechanism. Though YEC’s feel they have been able to model rapid subduction of the Earth’s crust (accounting for the mechanism), they certainly cannot explain how this process did not destroy the Earth’s surface in a giant heat death. Excess heat must have transferred to the oceans and the crust, which would destroyed all life on Earth.
  93. There is no evidence of excess heating from catastrophic plate tectonics. According to John Baumgardner, the excess heat diffused by evaporating a ~1.5-km-thick column of water over the oceans. He claims this is a answer to the ‘heat problem’ above, which he believes is physically “comprehensible”. But the geologic record shows no evidence of large scale heating of the oceans, such as might be expected in stable-isotope proxies that work as paleothermometers (such as δ18O and Mg/Ca in carbonates or δD in clay minerals).
  94. Cross section of oceanic crust at a mid-ocean ridge. Image from a lecture slide here.

    Cross section of oceanic crust at a mid-ocean ridge. Image from a lecture slide found here.

    Catastrophic plate tectonics cannot explain detailed formation of new oceanic crust, as is observed today at mid-ocean ridges. Oceanic crust is not a homogenous mass of basalt, but develops distinct textures from top to bottom, due to different cooling rates and chemical composition. If the ocean floor had to form rapidly (in a matter of years), we should not find these textures in older sections of oceanic crust, far away from modern spreading ridges.

  95. Seafloor basalt is modified geochemically by hydrothermal vents that form in fissures near mid-ocean ridges. These vents are powered by hot, upwelling seawater that originally infiltrated far away from the ridge, where temperatures are much cooler. However, the catastrophic plate tectonic model allows no time for this process and would have created a seafloor that was entirely too hot for effective hydrothermal circulation. Therefore, the catastrophic model is falsified by the thousands of studies of the ocean floor, which find evidence of alteration of seafloor basalts in very old parts of the crust (such as the western Pacific).
  96. Radiometric dating of seafloor basalt has produced a famously coherent pattern of increasing age away from mid-ocean ridges. The mapbelowis constructed by compiling thousands of analyses from dozensofindividual studies across the globe. Though young-Earth geologists will argueagainstthe validity of absolute ages, they still must explain the overall pattern, which makes no sense intheirparadigm (even invoking accelerated nuclear decay).

    Age distribution of the ocean floor; image and data compilation from NOAA.

    Age distribution of the ocean floor; image and data compilation from NOAA.

  97. The relative abundance of elements in the cosmos shows distinct patterns that make little sense in the young-Earth paradigm. For example, hydrogen and helium are super abundant compared to lithium, beryllium, and boron. Furthermore, elements of even atomic number are ~10 times more abundant than elements of odd atomic number. These relationships make sense in conventional astrophysics, because elements are produced over millions of years in dense stars through a process called nuclear synthesis. But YEC’s must explain them ad hoc:God simply created them like this.

    Relative abundance (on a logarithmic scale) of elements in our universe.

    Relative abundance (on a logarithmic scale) of elements in our universe.

  98. Components of our solar system, including the sun, meteorites, and planets, have approximately the same chemical composition (if volatile elements are excluded). This coincidence is shocking, unless we allow that each was drawn from a primordial mass, as described by the nebular hypothesis.
  99. Even the RATE team, a YEC think-tank seeking to undermine geochronology, has found no meaningful objection to the validity of radiometric dating techniques. Their proposal that radioactive decay rates increased by as much as a million times in the recent past is essentially a concession that geochronology works (they just refuse to accept the results), because…
  100. Accelerated nuclear decay is science fiction. Neither the physics nor the math produces a result in which radiometric dates yield consistently large ages for rocks and minerals in our solar system. One cannot tweak the physical properties of atoms, so as to increase the rate of radioactive decay, without all hell breaking loose—literally. Rates of decay depend on the stability of individual atoms, so if unstable atoms became more unstable, we’d expect stable atoms also to become very unstable, which would be the undoing of the physical universe as we know it. These are not conditions through which an Ark of humans and animals ever could have survived.

Scotland’s Verbose Expounditor of Geological Logorrhea

One of the pleasures of blogging is finding like-minded people. Recently, I wrote about a fossil discovery in Calgary, and the piece was picked up by Miksha, who lives there. Now Miksha has provided some extra insights about the greatest of Scots geologists, Hutton, whom I, an adoptive Scot, have discussed before, and I am happy to be able to return the compliment. But I think Hutton would have said “expositor”, and for my money, Lyell is a close competitor for longwindedness.

The Mountain Mystery

Pretty: along with The Flood, beauty was the principle concern of most pre-Hutton. geologistsPretty: Along with The Flood, beauty was the principle concern of most 17th century geologists.

James Hutton (1726-1797), Scotland’s most celebrated geologist, had a way with words. A rather awful way with words. But his scientific brilliance is uncontested. He is credited with moving geology away from the La-Z-Boy recliners of seventeenth century drawing rooms and onto the craggy cliffs where rocks are actually found. Until Hutton, gentleman-geologists were often preachers with parishes and parsonages to tend. They seldom ventured into the hills to study geology. If they collected rocks at all, it was the pretty ones they displayed in their cabinets. Such men philosophized about geology, Creation, and The Flood. They kept their fingernails clean. After Hutton, geology became the stuff of adventurers, travelers, experimenters, and above all, men and women with picks and hammers. Hutton was the founder of modern geology. He spurned divine intervention as the…

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The Deep Roots of Intelligent Design Creationism (Pt II of Kelvin, Rutherford, and the Age of the Earth )

Conservative politician caught lying. Learning from creationists. And the origins of plate tectonics. Last November, creationist objectors in Texas tried yet again to sabotage the state’s textbook adoption process. One of the objections concerned the age of the Earth, using the long refuted cooling argument that goes back to Kelvin in the 1860s. An online conversation about the matter directed me to the real flaw in Kelvin’s reasoning, which is different from what I had believed (see my earlier posting). Further digging led me to the oldest formulation I know of Intelligent Design (ID) creationism (of course, it was not called that, but “Unsolved Problems of Science”. Now over a century old, it already shows the key features of “modern” ID, even down to the link with conservative politics, and the despicable misuse of fraudulently edited quotations. Kelvin’s reasoning was based on a very simple physical model, heat flow from a solid sphere initially at uniform high temperature. This model, and estimates of the rate of heat flow and temperature gradient, led him to assign a maximum age of a mere hundred million years, with the most probable age around a quarter of that. And yet the argument from radiometric dating, something with which Kelvin himself was never happy, gives overwhelming evidence to the contrary. Rutherford, and everyone else for decades afterwards, thought that Kelvin’s error lay in the neglect of the heat generated within the earth by radioactive decay itself. Actually, it is a mistake to imagine that radioactive heating has all that much to do with it, and I must confess to having repeated this mistake many times in my own teaching and writing. The real error (details here and in Pt I)had been pointed out a decade before Rutherford confronted Kelvin at the Royal Institution, and three years before radioactivity had even been discovered. Kelvin’s calculation only considered heat transfer by conduction, whereas convection from depth is far more important. Convection can efficiently transport heat over long distances. It would have brought far more to the surface than Kelvin’s model allowed for, meaning that it must have taken far longer to get rid of it. John Perry, one of Kelvin’s own former students, was sure that Kelvin’s estimate of the earth’s age was far too low, suggested that Kelvin could have drastically underestimated the efficiency of heat transfer, and even suggested that the Earth’s interior could be in a partly molten state, making convection possible. In this piece, I want to talk about two things, how I learned the error of my ways, and exactly what it was that goaded Perry into an uncharacteristic public quarrel with his former mentor. I will also very briefly discuss the enormous importance of mantle convection for the present-day science of geology. First, the question of John Perry’s timing. If Kelvin had been promoting his cooling argument since 1862, why did no one query his physical assumptions until Perry did so in 1894? The answer, according to the historian Brian Shipley (now Canadian consul in Minneapolis), lies more in the domain of politics than of science.

The hall of Christ Church, Oxford, where Salisbury was awarded an honorary 4th class degree in mathematics (Public domain, through Wikipedia)

In the late 19th century, the annual meeting of the British Association for the Advancement of Science was an event of major importance. Presidential addresses had been given by Kelvin, by T. H. Huxley, and in 1892 by Sir Archibald Geikie, the most eminent British geologist of the time. In his address, Geikie tactfully thanked Kelvin for bringing physics to bear on the problems of geology, and for pointing out that thismeant that the earth could not be indefintley old as the geologists of half a century earlier had imagined. Nonetheless, he insisted that the Earth had to be much older than Kelvin would admit, and that therefore there must be some flaw, yet to be discovered, in Kelvin’s reasoning. In 1894, the Association met in Oxford. The Presidential Address was in part a response to Geikie. It was given by Lord Salisbury, a senior Conservative politician, who would be responsible for the Boer War among other things, and was the last Prime Minister to run his administrations from the House of Lords. Salisbury was extremely pessimistic by temperament, believing that “Whatever happens will be for the worse, and therefore it is in our interest that as little should happen as possible.” It is not surprising, then, that he was unsympathetic to the idea of evolution. Some of Salisbury’s remarks make one nostalgic for an earlier age, before the mid–20th century phenomenon of “scientific creationism”. “Few men”, he says, “are now influenced by the strange idea that questions of religious belief depend on the issues of physical research. Few men, whatever their creed, would now seek their geology in the books of their religion…”. Alas, this is exactly the way proponents of “creation science” would have us proceed, rejecting all evidence that cannot be fitted into a biblical framework. Salisbury also praises Darwin, and refers to the “lasting and unquestioned effect” of his work in disposing of the doctrine of the immutability of species, so that “Few are now found to doubt that animals separated by differences far exceeding those that distinguished what we know as species have yet descended from common ancestors.” But it is all downhill from there. File:Robert Arthur Talbot Gascoyne-Cecil, Vanity Fair, 1900-12-20.jpg

Salisbury, caricatured by Spy for Vanity Fair, 1900

 Salisbury accepts Kelvin’s estimates for the rate at which the Earth is cooling, asserts that according to these estimates organic life could not have existed on the Earth as it was 100 million years ago, and contrasts this with the requirements of the geologists and biologists, and “the prodigality of ciphers [zeroes] which they put at the end of the earth’s hypothetical life.” Natural selection demands well over a hundred million years; but according to the physicists, if the Earth even existed that far back in time it would have been so hot that all living things would have been vaporized. Faced with this disagreement, Salisbury proclaims himself neutral, but there is no doubt who he is neutral for. He puts forward various arguments from ignorance, which had more weight then than when creationists repeat them now. He also puts forward plausible arguments based on the improbability of matings between animals carrying favoured new variations. Those arguments were wrong, but this was not shown convincingly until the 1920s, with the development of statistical genetics, so we can forgive him. He also links the popularity of evolutionary thinking to Darwin’s own personality, and to disputes outside the domain of science itself, and predicts its decline. These themes, also, continue to resonate in the ID and other creationist literature. But, to be fair, they may have had more force at the time than they do now, more than a century later. What cannot be forgiven, however, is Salisbury’s editing, truncating, and reassembling quotations in such a way as to completely distort the meaning. This is a serious charge, and therefore requires detailed evidence. I can only apologise for the amount of space necessary for this. Distortion provides the basis for Salisbury’s most seemingly conclusive argument, which is philosophical, and hinges on an alleged quotation from a paper by the evolutionary scientist Weismann. The same Weismann to whom we owe our clear distinction between inheritance and development, genotype and phenotype. The relevant article, Contemporary Review, 1893, 64, 309-338, is titled “The All-Sufficiency of Natural Selection”, and Salisbury quotes from it as follows:

We accept natural selection, not because we are able to demonstrate the process in detail, not even because we can read more or less easily imagine it, but simply because we must – because it is the only possible explanation that we can conceive. We must assume natural selection to be the principle of the explanation of the metamorphoses, because all other apparent principles of explanation fail us, and it is inconceivable that there could yet be another capable of explaining the adaptation of organisms without assuming the help of a principle of design.

This, Salisbury would have us believe, demonstrates the ultimate bankruptcy of evolutionary theory. Invoking a principle of design is simply declared illegitimate, by arbitrary decree, so that natural selection can be accepted on faith. Wrenched from their context, Weismann’s words are paraded as evidence that evolution rests on assumptions as arbitrary as those of any religion. We are in the quote mine, territory all too familiar to students of creationism. Weismann is rebuked for dismissing “the help of a principle of design,” and thereby excluding the mood of explanation that now goes by the name of “Intelligent Design theory.” But that has absolutely nothing to do with what Weismann is actually talking about. Salisbury is neglecting context. Weismann is arguing, very specifically, with Herbert Spencer. What is at stake is not whether evolution occurs buthow it occurs, whether adaptations emerge within individuals through usage as organisms develop and live out their lives, or whether it occurs, as Weismann is correctly arguing, through selection between individuals. Actually, it’s worse. The two sentences that Salisbury runs together do not even belong together. Both sentences in the purported quotation come from Weismann’s article. The text of the second sentence, slightly longer than Salisbury’s version, is on p. 328. The first comes from considerably later on in the article, p.336, and the passage reads in full:

We accept it [natural selection], not because we are able to demonstrate the process in detail, not even because we can read more or less easily imagine it, but simply because we must – because it is the only possible explanation that we can conceive. For there are only two possible a priori explanations of adaptations for the naturalist – namely, the transmission of functional adaptations [as Weismann termed acquired characters] and natural selection; but as the first of these can be excluded, only the second remains.

In other words, Weismann and Spencer are already agreed on seeking naturalistic explanations, so that the question of a “principle of design” is not even under active consideration. Weismann, in the course of some 30 densely argued pages, is considering the competing explanations of evolved adaptedness, and makes his point by discussing how sterile worker insects come to be adapted to their way of life. He argues that only two such explanations are possible, namely the inheritance of acquired characters, and natural selection. But sterile workers cannot transmit acquired characters to their offspring, because they have none. Therefore the correct explanation must be natural selection; in this case selection for the ability to give rise to effective worker offspring. Weismann is not invoking extra-scientific arguments to exclude design; he is talking about something different altogether. Salisbury’s reading of Weismann is a contrived and unnatural distortion, made possible only by juxtaposing sentences that do not even belong on the same page, and in the wrong order to boot. Having misrepresented Weismann as an unwitting ally, Salisbury concludes his attack on evolution by natural selection with a quotation from Kelvin’s presidential address of 1871:

I have always felt that the hypothesis of natural selection does not contain the true theory of evolution, if evolution has been in biology…. I feel profoundly convinced that the argument of design has been greatly too much lost sight of in recent zoological speculations. Overpoweringly strong proofs of intelligent and benevolent design lie around us, and if ever perplexities, whether metaphysical or scientific, turn us away from them for a time, they come back upon us with irresistible force, showing us through Nature the influence of a free will, and teaching us that all living things depend on one everlasting [ever-acting?] Creator and Ruler.

I very much doubt if Perry had been following the lengthy and complex debate between Spencer and Weismann on the mechanism of evolution, but he would certainly have known of the various methods, such as the thickness of sediments, that geologists at that time were using to estimate the age of the Earth. To him, Kelvin’s much less generous estimate was the anomaly, and, when this estimate was invoked by someone of Salisbury’s eminence for semi-religious or even political purposes, that was enough to goad him into action. I found out about this all rather indirectly. As I admitted in my last post, one of my many vices is commenting in online forums. So when Jerry Coyne’s website, Why Evolution Is True, asked what cooling had to do with last November’s Texas textbook adoption drama, I wrote a comment that mentioned Kelvin and Rutherford. I also gave there, as an example of creationist absurdity, an alleged repudiation of Rutherford in a 1978 Institute for Creation Research pamphlet by Harold Slusher and T. P. Gamwell, cited by Bob Jones University. Just to be safe, I did a Google search on Slusher and Gamwell, and the only appraisal I could find dismissed their work, on the grounds that it had considered diffusion of heat across a plane surface, rather than the surface of a sphere. Reality, as always, is more interesting. My comment got a rejoinder from one Robert Seidel, who pointed out to me the paper by Englander and colleagues that I discussed on my last post. This, based on current estimates of radioactive heating, actually confirms Slusher and Gamwell’s conclusion, and in correspondence Englander told me that the difference between a plane and a sphere is quite unimportant in this context, since conductive cooling would only have penetrated in 5 billion years to one tenth of the Earth’s radius. But none of this really matters in the great scheme of things, because Kelvin’s argument, as we saw before, is swept aside by mantle convection. Conclusions: never take a quotation from a real scientist in a creationist text at face value. Strange things happen in the quote mine, as we have seen. But on the other hand, just because an argument refutes creationism, that doesn’t always mean it’s right. Just because an argument is used to support creationism, that doesn’t necessarily mean it’s wrong; quite probably, as in the Slusher and Gamwell case, it’s simply irrelevant. And just because something is said by creationists, that doesn’t mean there’s nothing to be learned from it. “Learn even from your enemies”, said Ovid, and he was right.

HolmesCropped2r A quick afterword (a complete afterword would invoke a large part of all geological studies for the past 40 years): by around 1930 it had become clear, from how the shockwaves caused by earthquakes travel, that the solid crust of the Earth floats on a viscous fluid, the mantle. Arthur Holmes, the most farsighted physical geologist of his generation, realised that this would imply mantle convection. He spelt out some of the implications of this in a remarkable paper in Transactions of the Geological Society of Glasgow. Heat would build up (see thumbnail) beneath over-large continents, attracting upward convective flow which would eventually tear them apart. New basaltic crust would appear at such separation zones, while old crust would disappear in regions of downward flow. Thus for the continents to move it it would not be necessary for them to force their way through basement rock, an obvious physical impossibility, but merely to ride on that moving basement like luggage on a conveyor belt. To use the language adopted a full generation later, when these ideas at last gained general acceptance, Holmes was describing rifting, subduction, and plate tectonics.  An earlier version of this post appeared in 3 Quarks Daily. I thank Philip England, Philip Kitcher, Peter Molnar, Brian Shipley, and one Robert Seidel (if you see this, Robert, please identify yourself so I’ll know just who to thank) for helpful discussions. I wrote to Prof Dan Olinger of Bob Jones University regarding his University’s portrayal of the Earth’s age in December 2013. He assured me that his colleagues would reply to my questions, but they have not yet done so.

Kelvin, Rutherford, and the Age of the Earth: I, The Myth

File:Lord Kelvin photograph.jpg

Lord Kelvin (Smithsoinian Instituion Libraries collection)

Kelvin calculated that the Earth was probably around 24 million years old, from how fast it is cooling. Rutherford believed that Kelvin’s calculation was wrong because of the heat generated by radioactivity. Kelvin was wrong, but so was Rutherford. The Earth is indeed many times older than Kelvin had calculated, but for completely different reasons, and the heat generated by radioactive decay has nothing to do with it.

Disclosure: in my introduction to the Scientific American Classic, Determining the Age of the Earth, and elsewhere, I have like many other authors repeated Rutherford’s argument with approval, without paying attention to Rutherford’s own warning that qualitative is but poor quantitative, and without bothering to check whether the amount of heat generated by radioactivity is enough to do the job. He thought it was but we now know it isn’t. It was only when chatting online (about one of the few claims in the creationist literature that is even worth discussing) that I discovered the error of my ways.

On the face of it, things could not be plainer. Kelvin had calculated the age of the Earth from how fast heat was flowing through its surface layers. An initially red hot body would have started losing heat very quickly, but over geological time the process would have slowed, as a relatively cool outer crust formed. His latest and most confident answer, reached in 1897 after more than 50 years of study, was in the range of around 24 million years.[1]

Yet on May 20, 1904, there was Rutherford, at the lectern of the Royal institution, talking about a piece of Cambrian rock, and announcing, on the basis of how much of its uranium had decayed to give lead and helium, that its age was some 500 million years. We even have Rutherford’s much quoted account of what happened next:

I came into the room which was half-dark and presently spotted Lord Kelvin in the audience, and realised that I was in for trouble at the last part of my speech dealing with the age of the Earth, where my views conflicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye and cock a baleful glance at me.

Then a sudden inspiration came, and I said Lord Kelvin had limited the age of the Earth, provided no new source [of heat] was discovered. That prophetic utterance referred to what we are now considering tonight, radium! Behold! The old boy beamed upon me.

This all seems clear enough. Rutherford is referring to Kelvin’s cooling argument. But this argument is invalid, because it assumes no new source of heat, and such a source exists, namely radioactivity.

The process that was overlooked in Kelvin’s calculations was also, indirectly, responsible for producing these folds.

Or so says the popular myth. The truth is more complex, and more interesting. For a start, Kelvin’s “prophetic utterance” did not refer to the Earth at all, but to a separate calculation of the age of the Sun. We know how brightly the Sun shines, and hence how rapidly it emits energy. If we knew how much energy it had to start with, and assumed that it wasn’t being added to, we could simply divide the initial amount by the rate of depletion, to estimate how long it would be able to shine. Kelvin performed such a calculation many times. As source of energy, he invoked the most intense source known to him, namely the gravitational energy released when the Sun collapsed from a diffuse cloud of gas to its present size. This led him to conclude in 1862 that the age of the Sun was in the range of 10 million to 100 million years (subsequently refined to around 20 million), and that “inhabitants of the earth can not continue to enjoy the light and heat essential to their life for many million years longer unless sources now unknown to us are prepared in the great storehouse of creation [emphasis added].” These are the prophetic words that Rutherford was referring to.

If Rutherford thought that the energy of radioactive decay was fuelling the Sun, he was greatly mistaken. The philosopher Auguste Comte had written in 1835 that we would never know the internal composition of the heavenly bodies.[2] He was wrong. Pass electricity through a gas or vapour, and it will emit light at specific frequencies that depend on the elements present (one familiar example is the sodium yellow of street lights). There are dark lines in the solar spectrum, and by 1860 the German chemist Kirchoff had shown that their frequencies match these characteristic emission lines.[3] So the chemical composition of the Sun’s outer layers was already well-known, and the fractional abundances of the heaviest elements, including almost all those that exhibit radioactivity, are quite negligible. And we now know, as Rutherford could not, that radioactive decay does not generate enough energy. Even if abundant supplies of the radioactive elements were concealed within the Sun’s interior, they would not suffice to fuel the Sun for Rutherford’s 500 million years, let alone the 4,500 million years, with as much still to come, required by current estimates.[4] It was not until 1920 that the source of the Sun’s energy was correctly identified as the fusion of hydrogen to helium, and while this was soon generally accepted, quantitative confirmation by measurements on the neutrinos produced had to wait until 2001. Using Einstein’s famous mass/energy equation and the masses of the isotopes involved, it is easy for us to calculate that the fusion of hydrogen to helium is some thirty times more productive of energy than the decay of the same mass of uranium to helium and lead; but Rutherford in 1904 could not have known of the relationship between mass and energy, or the precise masses of the relevant isotopes, or even that such things as isotopes existed.

But what about the age of the Earth itself, and Kelvin’s cooling calculation? This is what I had for many years assumed that Rutherford was talking about, and it turns out that radioactive decay is no real help here either. Measurements on granite in the early years of the 20th century suggested that radioactivity could fully account for the amount of heat being radiated out to space, and that the Earth might even be heating up. But we now know that granite is not representative of the Earth as a whole. The total rate of heat production by radioactive decay is currently estimated at around half the amount that the Earth emits to space, so simplemindedly we might imagine that this extends Kelvin’s calculation by a factor of two. Maybe a bit more, since by their nature radioactive materials would have been more abundant in the remote past, but this will not make much difference over the few tens or even hundreds of millions of years then under discussion. And even this grossly exaggerates the potential significance of radioactive heating, since all we need to consider is the heat generated in the outermost layers, from which heat has had time to diffuse the surface.

So how could Kelvin’s cooling argument be refuted? The correct argument had been put forward a decade earlier, before radioactivity had even been discovered, by John Perry, one of Kelvin’s own former pupils, and Kelvin had partly accepted the principle of Perry’s reasoning.

To understand what is really happening, we need to consider the different ways in which heat can be transferred. You may remember from school that there are three processes available; radiation, conduction, and convection. Radiation is the process by which the Sun, or the filament of an incandescent light bulb, glows yellow hot; or at lower temperatures the embers of a fire or the coals of a barbecue glow red hot; or, at yet lower temperatures, the Earth loses energy to the coldness of outer space by glowing in the infrared. It is not really relevant to the transmission of energy through opaque material such as rock. Conduction is simply the diffusion of heat through material, as the faster moving atoms of the hotter region jostle against, and share their energy with, their cooler neighbours. The third, and most efficient, heat transfer mechanism is convection. This is the physical movement of hotter material, carrying its heat with it, as in the roiling that takes place in the water when you boil an egg on a stove, or the pattern that forms in the film of oil in the pan if you prefer your eggs fried. Hotter material expands, making it less dense, so it rises to the surface, bringing cold material closer to the heat source.


Convection in a pan over a heat source. Warm (red) material is less dense and rises, allowing cold (blue) material to sink. Image by Eyrian through

Radiation is only relevant when we are talking about the transfer of heat through empty space, or through some transparent medium. Diffusion is simply the statistical spreading out of the extra heat in the hotter material, and is an inefficient process over long distances. By far the most efficient heat transfer mechanism is convection, but this can only take place in a fluid, where hotter and colder material can physically change places.

Back to Kelvin’s cooling rate calculation. This depended, among other things, on assuming heat transfer by conduction, and the rate of conduction was determined by actual measurements on rocks. Now imagine what would happen to Kelvin’s calculation if the actual heat transfer process were more efficient than this. The effect is the opposite of what you would at first imagine. Commonsense suggests that more rapid heat transfer would imply more rapid cooling. Not so. If heat transfer is limited, only a relatively shallow layer near the surface will have had time to contribute. If heat transfer turns out to be more efficient, the cooled layer will be correspondingly thicker, heat will have been conveyed from greater depths, and the total amount of heat conducted through the surface and lost to space will be correspondingly greater. But we know the total rate at which heat is being transferred, from the conductivity experiments and the rate at which temperature increases when we go down a mine, and this acts as a constraint on the calculation. Fixed rate, but a greater total amount because of more efficient heat transfer, implies a longer time. The cooling calculation can therefore be brought into line with Rutherford’s results, and indeed with the even longer times that we now know to be involved, if heat at depth is sufficiently more mobile than Kelvin had imagined.

In 1894, Kelvin’s former pupil and protégé, John Perry, had suggested higher heat transfer as a way of reconciling Kelvin’s age estimates with the hundred million years or so then required by the geologists. Kelvin, rather grudgingly, agreed in principle, and undertook to examine whether the thermal conductivity of rocks did increase as required at high temperature. [5] Within a few months, Kelvin reported a colleague’s response to this question; they did not. Indeed, Kelvin took the opportunity to review the entire question in the most extreme possible light, triumphantly lowering his best estimate of the age of the Earth to around 24 million years, noting that this was in good record with his estimates for the age of the Sun, and claiming that the burden of proof was now back with the geologists. Perry, in reply, drew attention to the fact that Kelvin had totally ignored the possibility that the Earth’s interior was or had been fluid enough to support convection, but Kelvin seems to have passed over this suggestion in silence.

A pity. Convection in the mantle, as we now call the region between the solid crust and Earth’s metallic core, is a cornerstone concept of modern geology. The implications of this, together with an explanation of why Perry waited until 1894 to challenge Kelvin’s calculations (which went back, as we have seen, to 1862 and earlier), and how I belatedly stumbled upon this story as a result of chatting online about the creationist literature, will be the subject of further posts.

An earlier version of this post was published in 3 Quarks Daily

[1] Detailed (and sometimes mildly discordant) scholarly studies hereherehere and here, and references therein.

[2] Comte, Positive Philosophy, Bk II Ch 1

[3] Annalen der Physik 185, 148–150, 275-301 (1860).

[4] Some radioactive elements, such as the newly discovered radium that Rutherford was referring to, do generate heat quickly, but that is because of their rapid decay rate, which implies short half-lives and rules them out as candidates.

[5] Perry, Nature 51, 224-227 (1895); Kelvin’s acknowledgement is at p. 227, his dismissive rebuttal at p. 438, and Perry’s final attempt at persuasion at p. 582.

The age of the Earth – how real science happens

If you want to teach about biology, or about the Bible, at Patrick Henry College for the evangelically home-schooled in Virginia, you will have to agree with the College’s view that “that God’s creative work, as described in Genesis 1:1-31, was completed in six twenty-four hour days.” Alternative views are to be presented, but should, “in the end, teach creation as both biblically true and as the best fit to observed data.”

Faculty teaching such courses might want to shield their eyes from the new Scientific American Classic, Determining the Age of the Earth, to which I wrote the introduction, for fear of having to change their minds and lose their jobs. For there they would find copies of articles, from 1857 to 1989, explaining in great detail just how, and after what exhaustive scrutiny, the scientific community was driven, much against its will, to conclude that “the best fit to observe data” requires a time of over 4.5 billion years.

Six days, of course, had long since ceased to be taken seriously as an estimate. The Scientific American account begins with Kelvin using arguments based on the then-new science of thermodynamics to challenge the geologists’ view that the earth was indefinitely old, and describes how he lowered his estimate from up to 100 million years to an upper limit of around 20 million. Meantime the geologists were developing what are sometimes called “hourglass” methods, based on observation of the Earth as it now is, and estimates of the rates of the processes that had brought it there. For instance, they  compared the total amount of salt in the oceans with the amount carried down in rivers annually. They added up the known thicknesses of sediments, and divided that by an estimated rate of deposition. This led them to estimates of around 100 million, enough (perhaps) for Darwinian evolution, but still longer than Kelvin was by the end willing to grant them.

When Rutherford’s group, followed in short order by Strutt, Arthur Holmes, and Bertram Boltwood, introduced radiometric dating, the geological community was initially sceptical. And with good reason. They were told that their careful estimates were wrong by a factor of five, then 10, and 20 or more. All this on the basis of a very poorly understood phenomenon. Remember that there was as yet no knowledge of the existence and nature of isotopes, the fact that there are three separate major decay sequences, or ways of distinguishing radiogenic from non-radiogenic lead. It was not until 1926, in fact, two decades after Rutherford’s initial work, that the method was generally accepted. And with our present knowledge, we can easily identify the flaws in the earlier reasoning, such as the inability to include the energy generated by nuclear processes, or the recycling of sediments back into the mantle. [Added edit: And, much more importantly, the role of convection in increasing the amount of heat to be disposed of; see here]

I had already written about this subject, mainly from the point of view of the conflict between Kelvin and the geologists. Nonetheless, I found it both enjoyable and instructive to retrace the thoughts of some of the scientists I had already met, and others whose names were new to me, in their own words and from the perspective of their own time. This was, for me, no mere antiquarian exercise, but an opportunity to experience for myself this wonderful story of discovery, not just from the point of view of the eventual winners, but as a journey over difficult terrain, where even concepts that we now recognize as misguided functioned, in their time, as signposts.

So what should we say about an institution of higher learning like PatrickHenryCollege? I would have preferred to say nothing at all, if it were not for the fact that it has an influence far beyond its numbers, that Professor John Lennox, whom I have discussed earlier, is speaking there next week, and that its 240-strong student body had by 2004 supplied seven out of the 100 interns in George W Bush’s White House, and support staff for 22 other politicians.


History of the plate tectonics concept

Interesting history of the plate tectonics concept, with a very prescient quote from Benjamin Franklin:

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