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23 Cards in this Set
- Front
- Back
fossils |
preserved remains of living things that are buried by sediments |
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mold |
a hollow area in sediment in the shape of an organism or part of an organism |
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cast |
a solid copy of the shape of an organism |
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petrified fossils |
fossils in which minerals replace all or part of an organism |
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carbon film |
an extremely thin coating of carbon on rock |
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trace fossils |
provide evidence of activities of an organism, for example dinosaur footprints |
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preserved remains |
remains of the entire organism in tar, amber, or ice |
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paleontologists |
scientists who study fossils |
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evolution |
the change in living things over time |
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extinct |
when an organism no longer exists and will never again live on Earth |
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sediment |
small solid materials that come from rocks or living things |
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sedimentary rock |
the type of rock that is made of hardened sediment, many fossils are found here |
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fossil record |
what scientists study to learn about the history of life, past environments on Earth, and how different groups of organisms have changed over time |
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relative age of a rock |
the age of the rock compared to the ages of other rocks |
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absolute age of a rock |
the number of years since the rock formed |
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law of superposition |
in undisturbed horizontal sedimentary rock layers the oldest layer is at the bottom., Each higher layer is younger than the layers below it. |
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extrusion |
Lava that hardens on the surface and forms igneous rock. Always younger than the rocks below it. |
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intrusion |
Magma pushing from below the surface, then cools and hardens into an igneous rock. Always younger than the rock layers around and beneath it |
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fault |
A break in Earth's crust. Always younger than the rock it cuts through. |
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index fossil |
a fossil that must be widely distributed and represent an organism that existed for a geologically short period of time. Useful in telling relative age of the rock layers. |
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radioactive decay |
process by which elements break down and release particles and energy. During this the atoms of one element break down to form atoms of another element. |
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half-life |
the time it takes for half of the radioactive atoms to decay |
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radioactive dating |
used by geologists to determine the absolute ages of rocks |