Radiometric dating lab
These were then eroded and Sedimentary Rocks B were deposited.The geologist may have found some fossils in Sedimentary Rocks A and discovered that they are similar to fossils found in some other rocks in the region.Here he can see that some curved sedimentary rocks have been cut vertically by a sheet of volcanic rock called a dyke.It is clear that the sedimentary rock was deposited and folded before the dyke was squeezed into place.Creationists would generally agree with the above methods and use them in their geological work.From his research, our evolutionary geologist may have discovered that other geologists believe that Sedimentary Rocks A are 200 million years old and Sedimentary Rocks B are 30 million years old.Such an interpretation fits nicely into the range of what he already believes the age to be.In fact, he would have been equally happy with any date a bit less than 200 million years or a bit more than 30 million years.
Should we use carbon 14 to date the fossil, or uranium 238 to date the volcanic ash layer, and why? We find samples of an igneous rock demonstrate it has been through 3 half-lives. If the parent isotope starts with 100 grams, but your samples yield only 6.25 grams of the parent isotope, how many half-lives have passed? What unstable isotope would be best to refine the date of bones found in a cave hearth built by humans between 20,000 and 40,000 years ago? Argue with the following: A stone tool fashioned from a chunk of obsidian yields a date of 3,000,000 years old, therefore, the tool was made by a human 3,000,000 years ago.The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.Thus, he already ‘knows’ that the igneous dyke must be younger than 200 million years and older than 30 million years.(Creationists do not agree with these ages of millions of years because of the assumptions they are based on.) Because of his interest in the volcanic dyke, he collects a sample, being careful to select rock that looks fresh and unaltered.
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Very small samples (less than 300 mg) are analyzed by accelerator mass spectrometry (AMS).