Re: [asa] radiometric question

If you go back 200-300 years obvious erupting volcanoes were well known eg Vesuvius Etna etc. In the Auvergne there are a series of volcanoes going back several million years. To the north by Clermont Ferrand there are the Puys. Before 1750 these were not thought to be volcanic but then by comparison with Vesuvius their volcanic nature was recognised and then the large older volcanoes of Puy Sancy and Puy St Mary ( We had a holiday there this May-June in abysmal weather but even so I climbed Puy St Mary and cycled over some of the passes up to 5000ft). Once this was recognised then other volcanic rocks could be recognised eg Arthurs Seat in Edinburgh and volcanics in Wales and Lake District and so on throughout the world. So be 1850 geologists could tell whether a volcano was new or ancient.

Now one can give a good guess from stratigraphic grounds .

So it is not so difficult

Michael
  ----- Original Message -----
  From: Dehler, Bernie
  To: asa@calvin.edu
  Sent: Tuesday, November 04, 2008 10:00 PM
  Subject: RE: [asa] radiometric question

  "The NAiG site mentions that the testing lab used by ICR is no longer doing K-Ar and, apparently, were clear that the tests were only accurate if the samples were not younger than 2 million years."

  Yes- but if you come across a volcanoe, how do you know if it is 300 or 300 million years old? If under 6,000 years old, then the test is no good, according to the link. I'm thinking there are other radiometric tests to use, but the article didn't seem to mention that. What would be nice to see is if they said "We took a sample from Mt. St. Helens and used a variety of tests and could determine the age correctly. The K-Ar test was out-of-bounds as we expected."

  .Bernie

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  From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of George Cooper
  Sent: Tuesday, November 04, 2008 12:42 PM
  To: asa@calvin.edu
  Subject: RE: [asa] radiometric question

  Hi Bernie,

  The site, keep in mind, is on the opposite end of the theological spectrum, which is one reason I thought it might be of interest since it digs a little deeper into the possible role of the ICR players. They do a fair job of pointing out why there is error in assuming that K-Ar (1.26 billion year half-life) would work at all with the Mt. St. Helen's samples, but you'll have to do better than me to get an accurate view of this. Admittedly, the test does appear to be a common one for igneous rock tests, which is obviously important for volcanic sampling.

  The NAiG site mentions that the testing lab used by ICR is no longer doing K-Ar and, apparently, were clear that the tests were only accurate if the samples were not younger than 2 million years. K-Ar is for dating the oldest things, not the youngest.

  I'm just no qualified to give a fair answer to your question, but others here can, I'm confident.

  Coope

  From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of Dehler, Bernie
  Sent: Tuesday, November 04, 2008 2:03 PM
  To: asa@calvin.edu
  Subject: RE: [asa] radiometric question

  Hi Coope- that was an interesting link. I read something in that link that wasn't clear to me, though. I could see a YEC saying that we weren't there when many volcanoes erupted, so let's pretend we didn't know when Mt. St. Helens erupted and see what the radiometric results reveal. Your link said this:

  Without properly referencing Bartelt et al.'s report, Swenson comments on one of the many criticisms of Austin's 'research':

  'One critic said that Dr Austin should not have sent young samples to the dating laboratory because it potentially puts "large error-bars on the data." By this reasoning, the method could not be used on any rocks, since, if we did not see the rocks form, how would we know whether they are young?'

   This is the old YEC 'only eyewitnesses can provide accurate histories' scam. Obviously, Swenson, like many YECs, fails to realize that scientists can successfully unravel past events without witnessing them. Forensic scientists frequently send criminals to prison without eyewitness testimony. To be exact, the recent hideous actions of the Washington DC area (USA) sniper(s) illustrate how unreliable eyewitnesses can be and how important forensic science is in solving crimes and stopping killers.

  I don't think the answer was very good. or the analogy of forensic science. For example, I guess if Mt. St. Helens had erupted 300 years ago- before our written history, we would get back very wrong old dates, correct? So in this case, we only know it is incorrect because we actually know when Mt. St. Helens erupted?

  In another post response Dr. Campbell said:

  "For example I know exactly what living mollusks would be very likely to give very old shells and modern bodies or vice versa with 14C. If a land snail lives on old limestone rocks, it's going to get a significant amount of the carbonate for the shell from the rock, and it will be old relative to the body. Mollusks that feed on chemosynthetic bacteria that use old hydrocarbons as an energy source are going to have old carbon in their bodies, but form the shell from reasonably modern carbonate in seawater."

  If you are trying to date the shells from animals that lived a few hundred or thousand years ago, how would you know their environment? There's no way to know what they fed on way back then, correct?

  .Bernie

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  From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of George Cooper
  Sent: Tuesday, November 04, 2008 10:27 AM
  To: asa@calvin.edu
  Subject: RE: [asa] radiometric question

  Bernie,

  You might enjoy this site regarding the K-Ar testing of Mt. St. Helens.

  http://www.noanswersingenesis.org.au/mt_st_helens_dacite_kh.htm

  Coope

  From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of Dehler, Bernie
  Sent: Tuesday, November 04, 2008 11:36 AM
  To: asa@calvin.edu
  Subject: [asa] radiometric question

  I went to talk origins to learn about radiometric dating, and was happy to see it referred to this ASA article:

  "Radiometric Dating - A Christian Perspective"
  http://www.asa3.org/ASA/resources/Wiens.html

  I have a question. It says:

  14. A young-Earth research group reported that they sent a rock erupted in 1980 from Mount Saint Helens volcano to a dating lab and got back a potassium-argon age of several million years. This shows we should not trust radiometric dating.

  There are indeed ways to "trick" radiometric dating if a single dating method is improperly used on a sample. Anyone can move the hands on a clock and get the wrong time. Likewise, people actively looking for incorrect radiometric dates can in fact get them. Geologists have known for over forty years that the potassium-argon method cannot be used on rocks only twenty to thirty years old. Publicizing this incorrect age as a completely new finding was inappropriate. The reasons are discussed in the Potassium-Argon Dating section above. Be assured that multiple dating methods used together on igneous rocks are almost always correct unless the sample is too difficult to date due to factors such as metamorphism or a large fraction of xenoliths.

  Let me ask a clarifying question. Suppose a YEC takes a rock from Mt. St. Helen's and asks for a date due to radiometric dating. I assume various dating methods will be used. will they get the correct recent date? I didn't see a clear, blunt, answer.

  .Bernie

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Received on Tue Nov 4 18:13:55 2008