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Rock Cycle
definitions and processes
Term | Definition |
---|---|
Sedimentary Rock | Rock formed from compacted sediment or dirt |
Igneous Rock | Rocks formed by the cooling and solidifying of molten materials. |
Metamorphic Rock | Rock that has changed due to heat and pressure over long periods of time |
Fossils | Evidence of past earth life |
Index fossils | Fossils that date to a specific era of geologic time. Used to help relatively date rocks |
Trace fossils | a fossil of a footprint, trail, burrow, or other trace of an animal rather than of the animal itself. |
Relative Dating | A method of dating rock layers or fossils based on the Law of Superposition. Does not give an actual age of a rock or fossil, but rather the order of events compared to other rock layers. |
Absolute Dating | A method of dating rock layers or fossils based on analysis of the radioactive materials found in them. Age is measured in half lives. |
Cenozoic Era | Period of geologic time in which mammals were dominant and humans begin to appear. |
Mesozoic Era | Period of geologic time in which large reptiles and dinosaurs were prevalent. |
Paleozoic Era | Period of geologic time in which most life was found in the oceans. |
Pre-Cambrian Era | Period of geologic time in which mountain, oceans and the atmosphere was forming. Life on earth was believed to be microscopic organisms. |