USGS site misleads teachers and school children about dating

posted in: Dating | 8

I was fascinated by the material provided for school teachers by the US Geological Society about dating rocks.

For a classroom activity they suggest:

Have your students look for evidence of date stamps and cornerstones on their walk home. Depending upon your area, there may be quite a few.

Duh!  Building stones may have date stamps but rocks do not. This suggested activity makes the point, if anyone is alert to see it, that the only reliable way of knowing the age of anything is by the historical method, which relies on eyewitnesses and a written record. That is what the Bible is and why the Bible is the only reliable way of knowing the age of the earth.

More intriguing, they state the key concepts of the lesson as:

  • Most rocks have tiny amounts of radioactive material in them.
  • Radioactive elements decay (they change into a completely different element — for example, Uranium which is used in nuclear reactors changes into Lead, a very dense metal).
  • Scientists use precise laboratory equipment to measure the amount of the new material that was created by radioactive decay.
  • By knowing how fast certain elements decay, we can calculate the age of rocks (the number of years since the rock formed).

It all sounds very precise and technical but they leave out a key fact.  It is impossible to calculate the age of a rock from such information because we need to know the radioactive content of the rock when it formed as well as the entire history of the rock until the sample was collected. In order to calculate a date the geologist first has to assume the geological history of the rock. In other words, all radioactive ages quoted are “guesses”, in that they are based on assumptions about the past.

The article is also wrong about its description of the dating of Grand Canyon.

Grand Canyon National Park, Arizona … In order to determine the age of an individual layer, a geologist must collect a sample of that layer and take it back to the lab. The geologist uses precise laboratory machines to analyze the relative abundance of radioactive atoms and atoms that form as a result of radioactive decay. Finally, the geologist can calculate the rock’s age. This calculation requires knowledge of math, physics, and chemistry! Note how the oldest rocks in the Grand Canyon are on the bottom and the youngest rocks are on the top.

Once again it all sounds very precise, technical and complicated. It seems designed to impress teachers and school children.  But it is not true. The layers in the wall of Grand Canyon are sedimentary layers and sedimentary layers are not dated by radioactive methods, which are applied to igneous rocks. Rather, the sedimentary layers in Grand Canyon were “dated” using their contained fossil assemblages.

Check this article to see how radioactive dating works. This USGS item omits discussion on the fundamental problem facing every dating method—their fatal flaw.  All radioactive dates are based on assumptions.

The USGS should fix this piece so it does not mislead teachers and school children.

8 Responses

  1. Winston Broad

    Thanks again Tas for the info. I sure wish we could get the truth through to all teachers and kids, but I CAN book Grandad Days with each of my 7 grandkids as they get into upper primary school to share personally with them about the living God revealed in His Word. I’ll make a timeline of human history with each of them and share how the facts of real science beautifully verify and fill out God’s account — not that He needs our verification, but it sure helps open up wide eyes of dawning and understanding!
    Would it be OK to drop in to see you with them sometime soon in Eight Mile Plains (if you’re in town) — maybe you’d do Macdonald’s with us and share with us personally some more of those truths you explain so well?
    I thank God for your continuing work to show how the evidence keeps pointing to God as our Creator and therefore our Lord and Saviour! Right on bro Tas!
    Winston Broad – Coomera

  2. Isaac

    I have something to admit, up front: I am a Jew.
    While your reasoning makes sense, it is wrong in some points. Radioactive decay can be measured precisely, using potassium 40 -argon decay. As argon is a gas, it can only be inside a rock if it formed there by radioactive breakdown. Therefore, if you measure the amount of argon and the amount of potassium 40 in a rock, you can find its age precisely. If there are equal amounts of both, it is one half-life old, or 1.248 billion years old. this is how we know, absolutely, how old the earth is.

  3. Tas Walker

    Hi Isaac:

    You have a great heritage in the Scriptures and I am a reader and believer in the writings of Moses and the Prophets. I am also indebted to your blood brothers, the Apostles, who recorded the events in Israel some 2,000 years ago.

    Yes, radioactive decay rates can be measured—in the present—but we can only assume they were the same in the past. This is not a scientific observation but a philosophic assumption and may not have been the case (Geologist Andrew Snelling discusses this possibility here).

    Argon gas is commonly trapped in rocks when they crystallize, so common that it is given a name—”excess argon”. (Some examples: Mt St Helens and Mt Ngauruhoe).

    The age of the earth was not determined by K-Ar dating (See The dating game.)

  4. Joe Meert

    Radiometric dating is not perfect. The rocks are not perfect recorders of Earth history, but these imperfections can be dissected out of the analyses on the rocks. You cite ‘excess argon’ as a problem, but fail to document how ‘excess argon’ is determined. The very fact that excess argon can be discovered tells us something about how well geochronological analyses are able to handle the complications of nature. Furthermore, I find it interesting in a philosophical sense that you discuss the possibility that rates of decay may be variable. If true, then you must also admit that rates could have been much slower in the past meaning that our estimates for the age of the earth are way TOO young! In short, you engage in the type of wishful and close-minded thought that is modus operandi for young earth creationist apologists. Please take me off your e-mail list.


    Joe Meert

  5. Tas Walker

    Hi Joe, I love your sense of humor: “you engage in … close-minded thought. Please take me off your e-mail list.”

    The only way that excess argon can be identified is when the age turns out to be too old. You can’t identify the 40Ar isotopes that were generated by the radioactive decay of K from those that were not.

    The Ar-Ar method was supposed to be able to identify excess argon from the shape of the spectra. But even when the plateau is satisfactory, if the calculated age is too old then some story will be concocted to explain how the excess argon was incorporated into the sample.

  6. David

    What happens if the rock that one is trying to date get reheated or remelted? Does the percentage of both Potassium and Argon stay the same or does it change? Would this then alter the dates that come from the sample?

  7. Tas Walker

    Hi David: If the region is reheated or remelted it violates one of the essential assumptions that the system has remained closed. If the date turns out to be younger than expected geologists routinely invoke a heating event to explain loss of argon.

  8. Peter Frageorgia

    Hi Taz,

    There are several other assumptions about this kind of radioactive dating:
    1) The decay are fixed. This has been recently disproved. Radioactive decay rates vary according to the neutrino emissions of the sun. With a higher neutrino exposure there will be corresponding increase of the rate of decay.
    2) The ignoring of isotopes that don’t fit into the dating scheme. For example, the decay of O18 into O16. Using the same methodology that is used for K->Ar will date rocks older than the supposed data of the ‘Big Bang’.