fossil - the preserved remains of once living things, mold - a hollow area in sediment in the shape of an organism or part of an organism, cast - solid copy of the shape of an organism, petrified fossil - fossil in which minerals replace all or part of the organism, carbon film - a fossil formed from an extremely thin coating of carbon on rock, trace fossils - fossilized evidence of organisms, extinct - an organism that no longer exists, relative age - the age of rock compared to the ages of other rock, absolute age - the number of years that have passed since a rock formed, extrusion - lava that hardens at the surface, intrusion - magma pushing through existing rock layers and hardening, fault - a break in the Earth's crust, index fossil - a fossil that can help determine the relative age of the rock, radioactive decay - the atoms of one element break down into the atoms of other elements, helping age rocks, half-life - the time it takes for half of the radioactive atoms in rock to decay, geologic time scale - a record of the geological events in Earth's history, mass extinction - a time when many types of living things become extinct at the same time.,

Fossils and Rock Dating

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