| A | B |
|---|
| super position | oldest rock is on the bottom; |
| relative dating | a general dating technique (strategy); to determine what is older and younger; start at the bottom and proceed to the top |
| extrusion | igneous material that cuts through rock and erupts at the surface |
| intrusion | igneous material that cuts through rock without exposing itself at the surface; an internal process when magma squeezes between layers of pre-existing rock |
| fossil | remains of once living things, reveal alot about life forms |
| correlation | a way of determining which rock layers match from one place to another |
| index fossil | found in many locations but lived for a short period of time, used to date rock layers |
| unconformity | an area of erosion that creates a gap in geologic time; when a new layer of rock is laid down on a surface left by erosion, it forms a buried erosion surface |
| absolute dating | a specific dating giving numeric ages; |
| half-life | the time it takes for one half of the rock to decay |
