It is clear that the sedimentary rock was deposited and folded before the dyke was squeezed into place.By looking at other outcrops in the area, our geologist is able to draw a geological map which records how the rocks are related to each other in the field.From the mapped field relationships, it is a simple matter to work out a geological cross-section and the relative timing of the geologic events.His geological cross-section may look something like Figure 2.
It has been established through extensive experimentation that radioactive decay occurs at a constant rate. In this case, the initial condition is the amount of daughter isotope in the rock when it was formed.What I want to do in this video is kind of introduce you to the idea of, one, how carbon-14 comes about, and how it gets into all living things. They can also be alpha particles, which is the same thing as a helium nucleus. And they're going to come in, and they're going to bump into things in our atmosphere, and they're actually going to form neutrons. And we'll show a neutron with a lowercase n, and a 1 for its mass number. And what's interesting about this is this is constantly being formed in our atmosphere, not in huge quantities, but in reasonable quantities. Because as soon as you die and you get buried under the ground, there's no way for the carbon-14 to become part of your tissue anymore because you're not eating anything with new carbon-14.And then either later in this video or in future videos we'll talk about how it's actually used to date things, how we use it actually figure out that that bone is 12,000 years old, or that person died 18,000 years ago, whatever it might be. So let me just draw the surface of the Earth like that. So then you have the Earth's atmosphere right over here. And 78%, the most abundant element in our atmosphere is nitrogen. And we don't write anything, because it has no protons down here. And what's interesting here is once you die, you're not going to get any new carbon-14. You can't just say all the carbon-14's on the left are going to decay and all the carbon-14's on the right aren't going to decay in that 5,730 years.Then the computed age based on the accumulation of daughter products will be incorrect (Stasson 1998).In order to use the valuable information provided by radiometric dating, a new method had to be created that would determine an accurate date and validate the assumptions of radiometric dating. Isotope dating satisfies this requirement, as daughter products do not decay back to the original parent element.