Geology is the study of the composition and physical properties of rocks, minerals, gems and other related earth materials, including diamonds and crystals.
Scientists gain an understanding of the Earth's history by studying its composition.
("87" is the atomic mass number = protons + neutrons.
Numerical ages have been added to the Geologic Time Scale since the advent of radioactive age-dating techniques. In theory, the age of any of these minerals can be determined by: 1) counting the number of daughter isotopes in the mineral, and 2) using the known decay rate to calculate the length of time required to produce that number of daughters.
Geologic Processes Geological processes have helped to create many iconic features on Earth.
Processes, such as plate tectonics, are what shapes the face of the Earth.