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Earth History
A Trip through Geologic Time
Term | Definition |
---|---|
Fossil | the preserved remains or traces of living things in different types of rocks or other mediums. |
Mold | Type of fossil that is a hollow area in sediment the shape of an organism or part of an organism. |
Cast | Type of fossil that is a solid copy of the shape of an organism. |
Trace fossils | Type of fossil that provides evidence of the ancient organisms like foot prints. |
Relative Age | Age of a fossil or rock compared to the ages of other rocks or fossils. |
Absolut Age | The age of rock in number of years since formation. |
Law of Superposition | In horizontal rock layers, the rock layer that is on the bottom will be the oldest layer. |
Unconformity | The surface where new rock layers meet a much older rock surface beneath them. |
Index Fossil | A fossil that tell the relative ages of the rock layers in which they occur. |