Geologists can measure the paleomagnetism of rocks at a site to reveal its record of ancient magnetic reversals. A particular isotope of a particular element is called a nuclide. With uranium-lead dating, for example, the process assumes the original proportion of uranium in the sample. The age of the earth. The disintegration products of uranium". The students find it quite engaging.
Other Topic Rooms Ecology.
Dating Rocks and Fossils Using Geologic Methods
There is no reason to expect that the rate of decay of a radioactive material is largely constant,  and it was almost certainly not constant near the creation or beginning of the universe. Most isotopes found on Earth are generally stable and do not change. Kramers June For example, when potassium is incorporated into a mineral that forms when lava cools, there is no argon from previous decay argon, a gas, escapes into the atmosphere while the lava is still molten. Earth Science Basics.