Radiometric dating of sedimentary rocks recently dating valentines day
As the rock cools, there comes a point, called the closing temperature, when parent and daughter isotopes can no longer diffuse into or out of the rock system—at that point, the clock is set.(It’s worth mentioning that this temperature varies by rock type and by isotope!It’s just that I kept adding and adding to make it all make more sense and before I knew it, I had 3000 words on dating fossils! So, last time, we discussed the basics of radiometric dating and ended with a quick and dirty example of how a parent:daughter isotope ratio can be used to find the age of a sample.I skipped some details on purpose, but the foundational principles to these methods are really as easy as I explained.I asked in the caption to this figure, “How do you know C happened before D? If you’re familiar with the colors and patterns used in geologic diagrams like this, you probably know that D is an igneous intrusion and C is a layer of sedimentary rock.So we know that C came before D—but because D is igneous, we can put a date on it (now I have a Beyoncé song in my head, great…).
So maybe somewhere else, a correlated bed of this sedimentary rock sits on top of a layer of igneous rock that is 160 million years old—then our temporal window for C has shrunk to 10 million years. but with a few more localities thrown into the mix, geologists can narrow it down further. Unless you teach high school or college Earth science or perhaps chemistry, most of this information may fall outside your curriculum.
However, that doesn’t mean that you can’t help to push against the misconception that all fossils are dated directly.
Most obviously, you yourself can be careful not to suggest that fossils are dated directly.
So it’s not like there is one magic temperature that locks these things in. Carbon-14 is a radioactive form of carbon that is widely used in radiometric dating.
It’s all a bit mathy, but the good thing is, people have figured it out and can account for it no matter the rock type or the radiometric method being used.) But, when it comes to fossils, we’re primarily interested in sedimentary rock layers, which, you’ll recall, form from pre-existing rock material. Very occasionally, there may be some remaining organic material in a fossil that could, hypothetically, be dated using carbon-14.See some good or bad examples of science communication lately?