The universe is full of naturally occurring radioactive elements.Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms." When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.But for the evolutionist, billions of years is the assumption.Ask an evolutionist how he knows the Earth is this old and he will probably tell you something about fossils, rocks, and dating methods.Yet in most cases, people I’ve talked to know little about how these methods actually work.No one has a time machine to go back and be an eyewitness of the origin of the universe, but a whole lot is riding on the accuracy of these claims.Chapter 12: Geologic time A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012), from the National Research Council of the National Academies. Radioactive decay lifetimes and isotopic content in rocks provide a way of dating rock formations and thereby fixing the scale of geological time.College Board Standards for College Success: Science ES.3 Earth’s History: Relative and Absolute dating.
There is a good picture of an actual unconformity in America here.
Students understand that various dating methods — relative and absolute — have been used to determine the age of Earth. Between Earth Science and Other Disciplines: Evidence of Common Ancestry and Divergence (LS.1.1); Living Systems and the Physical Environment (LS.3.1); Nuclear Chemistry (C.1.6); Nuclear Interactions and the Conservation of Mass–Energy (P.2.3) Benchmarks: American Association for the Advancement of Science.
Knowledge of radioactivity helps them understand how rocks can be dated, which helps them appreciate the scale of geologic time…
Scientific evidence indicates that some rock layers are several billion years old.
The Bible has records that show about a 6,000-year history back to the beginning.