| A | B |
|---|
| absolute age | the number of years since the rock formed. |
| fossil | The preserved remains or traces of living things. |
| cast | A fossil that is a copy of an organism's shape, formed when minerals go into a mold. |
| carbon film | A type of fossil that has a very thin coating of carbon on rock. |
| trace fossil | A type of fossil that provides evidence of the activities of ancient organisms. |
| preserved remains | Remains that have no change or little change. |
| law of superposition | In horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it. |
| extrusion | An igneous rock layer formed when lava flows out of the Earth and hardens. |
| intrusion | An igneous rock layer formed when magma hardens inside the Earth. |
| fault | A crack in Earth's lithosphere along which the rocks move. |
| unconformity | A place where an old, eroded rock surface is in contact with a newer rock layer. |
| index fossil | You can find this fossil in many places and it was an organism that lived during only one short period. |
| relative age | The age of a rock compared to the ages of other rocks. |
| petrified fossil | A fossil in which minerals replace all or part of an organism. |
| mold | A fossil formed when an organism buried in sediment dissolves, leaving a hollow area. |
| Carbon Dating | a method of estimating age on organic materials (once living). |
