What happens when a speaker gives a talk about dinosaurs but doesn’t have any training in geology or paleontology? You could get a string of distortions of both of these fields of inquiry and even problems keeping facts straight. A few weeks ago I witnessed just such a talk when I attended an Answers in Genesis conference at a local church. The final evening included a talk by Tommy Mitchell entitled: Jurassic Prank: A Dinosaur Tale. Mitchell shared with his audience clips from the movie Jurassic Park using them to illustrate how scientists have conned the public into believing that dinosaurs went extinct long ago and that they were living with humans up until “at least the last few hundred years.” Last week I wrote about this very same talk and showed that Mitchell was confused about what we can know about history (see: Historical Science: How do We Know a Fish Fossil is a Fish Fossil).
In the 52-minute mark in the video below, which was recorded more than 2 years ago but is 95% the same as the talk I heard, you can hear Tommy Mitchell talk about the asteroid impact theory for the demise of the dinosaurs. Here he explains that a giant asteroid is supposed to have thrown up a lot of dust which killed the dinosaurs. He also draws the attention of the audience to a part of the asteroid story that they are likely familiar with. He references the iridium layer by stating that “some of these layers of rock where you find dinosaur fossils you find high levels of a substance called iridium.” Mitchell then goes on to explain why this is a huge problem for the asteroid theory of extinction. He asks how a thin layer of dust with iridium could have preserved a huge T. rex. He says that huge amounts of sediment would be needed and that could only be provided by a massive worldwide flood. Then he proposes that the iridium layer is the result of volcanic eruptions during the Flood.
The problem with his story is that he is the one who has, even if inadvertently, told a dinosaur tale. If Tommy Mitchell had any experience with dinosaur paleontology he would have know that there are NO known dinosaur fossils in the iridium-spiked sediment layer of the geological column. But he tells his audience about these fossils as if their existence were common knowledge and then proceeds to talk about how these fossils are a huge problem. His audience, and possibly Mitchell himself, is completely unaware that he has created and answered a problem – dinosaur fossils in a thin layer of dust – that doesn’t exist.
What is the iridium layer and what does it tell us?
It is true that there is a geological mystery surrounding dinosaurs. That mystery involves explaining why dinosaur fossils have only ever been found in sedimentary rocks of three geological periods of the Mesozoic Era. Suddenly at the end of the Cretaceous Period dinosaurs disappear from the fossil record. But Mitchell probably doesn’t want to acknowledge this very obvious feature of the fossil record because he believes dinosaurs survived the Flood on Noah’s ark and roamed with man until very recently and thus the lack of fossils in the upper portion of the fossil record is an unsolved mystery for young earth creationists.
The sudden cessation of dinosaur fossils is marked by a very distinct feature in the geological column where Cretaceous and Paleogene rocks are found next to each other: a thin layer of sediment characterized by the presence of a high amount of low-abundance element, Iridium. The discovery of what is called the iridium anomaly led physicist Luis Alvarez and colleagues to propose that this was caused by a large asteroid impact. Because this impact deposit is found globally above the last dinosaur fossils it has become a leading proposal (see footnote 1) to explain the mystery of why the dinosaurs went extinct.
What Tommy Mitchell didn’t mention is the presence of iridium isn’t the only evidence that provides such a compelling case for a massive impact event. In most of the northern hemisphere just below the iridium layer is a layer of tektites which are a distinct form of glass sphericals. These are formed in high impact collections when rocks are melted quickly and thrown up in the air and then almost instantly “freeze” again in small glass spheres. These spheres then rained down on the Earth before the finer iridium dust from the vaporized asteroid fell out of the sky. In the image below there is a picture of such spheres from Italy at the Cretaceous/Paleogene boundary and off the east coast of Florida. In the later core section, the tektites stand our very clearly from the typical fine particles that rain down on the bottom of the ocean. The thickness of these tektite deposits generally increases the closer one gets to the Yucatan Peninsula in Mexico which has since been identified as the point of impact.
Did the asteroid impact create the dinosaur fossils we see today?
As I mentioned above, what may surprise many of you is that to-date no dinosaur fossils has ever been found in the iridium layer. In 2011 a dinosaur fossil was reported from 5 inches below the Iridium layer making it the closest dinosaur fossil to be found thus far. (http://news.yale.edu/2011/07/12/last-dinosaur-mass-extinction-discovered) So, the event that may have resulted in the extinction of dinosaurs is not what created all the dinosaur fossils.
As surprising as this may be to you this is not a particular shock to paleontologists. Even if hundreds of thousands of dinosaurs had been killed in North America as a result of an asteroid blast and following environmental damage the lack of fossils in sediments deposited by that blast would not be shocking. Most dinosaurs would simply have decayed where they died just as they would have done when they died in the years before the asteroid impact. Hence, just like any other time in history, only a very small fraction of those dinosaurs that died would have found themselves in conditions favorable for long-term preservation. And of that small number only an astonishingly small number would be expected to be found in the very few places we find the iridium layer exposed at the surface for us to investigate. So it is not surprising that we have yet to find a dinosaur fossil at the very moment implicated in their final extinction (see footnote 2).
All dinosaur bones that have been discovered, such as those I have seen at Dinosaur National Monument, were deposited long before the asteroid event and their preservation were due to other natural causes such as local river floods or large volcanic explosions. These represent more favorable conditions for fossilization.
Could the iridium layer have been deposited in a Global Flood as Mitchell proposes?
Once again, Mitchell is misleading his audience. Iridium is sometimes found at elevated levels in volcanic ash but even when there is more iridium it doesn’t reach the concentrations seen in the iridium anomaly at the K-Pg boundary. But most telling is that Mitchell doesn’t tell his audience that the concentrated iridium layer is quite thin and so represents a very distinct spike in iridium concentration in the geological column. The iridium appears very suddenly all over the northern hemisphere and then gradually is reduced in concentration in the sediments above the spike. This is consistent with a sudden dramatic event followed by gradually diminishing amounts of iridium in the atmosphere and reworked sediments deposited on top of the main iridium deposits.
But it isn’t just the iridium that doesn’t fit Mitchell’s volcanism explanation. As I mentioned before, this iridium either sits right above or mixed in with a layer of glass spherules (tektites) which are distinctive features of a cosmic impact not of volcanic eruptions. The one-two punch of increased iridium and glass spherules found at the same locations is the smoking gun of a massive impact. These tell-tale signs of impact sit right at the boundary that separates dinosaur-bearing rock and all rock above that contains no dinosaurs. This correlation of factors makes no sense if the sediments were all deposited at one time in a global flood. Flood waters would not be able to be concentrate iridium in sediments in a water column, nor could dinosaur bones be sorted in this fashion.
Just to add one more bit to the story, the iridium layer also contains a high amount of soot which are particles resulting from the burning of plant matter. It is proposed that this is evidence that huge forest fires were set off by the asteroid impact. A layer of sooty particles makes no sense in sediments laid down during a global flood.
So what’s the problem?
The problem is that Tommy Mitchell lack of specific knowledge of the fossil record has resulted in his presenting a false understanding of fossils to his audience. He hasn’t provided any real answers at all. He trivializes the facts by either not mentioning important ones or by simply getting his facts wrong.
It is not surprising that someone not familiar with the fossil record of dinosaurs might believe that many dinosaur fossils are the direct result of the asteroid impact. But, Tommy Mitchell is an expert in the eyes of the audience and as such he has a responsibility to be better informed than his audience rather than subject to the same misconceptions. He has a responsibility to get his facts right and present his opponents views accurately. Unfortunately, the many errors in his talk can’t be dismissed as just the result of hasty production. Mitchell has been giving this same talk for at least 2 years. Every word in this talk has been carefully constructed to influence they audience toward a particular view of dinosaurs.
Mitchell even makes a plea to his audience to become informed about dinosaurs because he says it is critical that Christians have answers to dinosaur questions. He is worried that our kids will learn answers about dinosaurs from the world rather than the Bible and thus parents need to educate themselves about dinosaurs and teach our kids these answers. He even pulls out a piece of 1 Peter 3:15 to emphasize the importance of understanding dinosaurs, “… be ready always to give an answer….” That is the Answers in Genesis motto. Always have an answer and AiG will provide you with answers to all your dinosaur questions in their books and videos. But what good are answers if they are based on misconception and poor scholarship?
1. The asteroid-impact theory isn’t the only popular theory that might explain the extinction of dinosaurs. Some geologists have proposed that massive volcanism might have been the real culprit. Recent evidence suggests that it could have been a one-two punch. Even if the asteroid didn’t cause their complete extinction, this event does coincide with end of the dinosaurs.
Renne, Sprain, et al. 2015. State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact. Science 350 (6256): 76-78.
2. There have been few reports of possible dinosaur bones found in layers of rock in the Paleogene just above the end of the Cretaceous. It is certainly possible that some dinosaurs managed to survive for some period into the Paleogene but many of these fossil finds are not conclusive because the bones could represent erosion of bones from sediments deposited before the impact layers and then deposited on top of impact layers. For example a dinosaur was buried in a stream bank in the Cretaceous period but then a fossil bone was eroded out of that stream bank and the bone transported downriver and re-deposited in new sediments which then turned to rock later. The fossil then is actually much older than the rock it is found in.
Alvarez L.W., Alvarez W., Asaro F., Michel H.V. (1980) Extraterrestrial Cause for the Cretaceous-Tertiary Extinction, Science 208, 1095-1108. E-Text (PDF; 1,0 MB)