| A | B |
|---|
| beta decay | the process in which one of an isotope's neutrons breaks down into a proton and an electron and the electron leaves the atom as a beta particle |
| carbonaceous film | fossil formed when an outline of the original organism is formed from left-over carbon |
| cast | made when sediments fill in a cavity made when an object decayed and the sediments harden into rock |
| half-life | the time it takes for half of the atoms in an isotope to decay |
| index fossils | fossils of species that lived on Earth for short periods of time and were abundant and were widespread geographically |
| principle of superposition | states that for undisturbed rocks, the oldest rocks are on the bottom and the rocks become younger and younger toward the top |
| mold | hollow pace in rock made when an organism died and was buried and holes in the rock let air or water reach it and dissolve the organism |
| radiometric dating | the process of calculating the absolute age of a rock by measuring the amounts of parent and daughter materials in a rock and knowing the half-life of the parent |
| radioactive decay | a process that uses the properties of atoms in rocks and other objects to find their ages |
| relative dating | the order of events and the relative age of rocks is determined by examine the position of rocks in a sequence |
| unconformities | gaps in rock layers that develop when agents of erosion remove existing rock layers |
| uniformitarianism | states that Earth processes today are similar to those that took place in the past |
