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6th Grade Chapter 10
A Trip through Geologic Time
| Question | Answer |
|---|---|
| fossil | the preserved remains or traces of an organism |
| petrified fossil | a fossil formed when minerals replace all or part of an organism |
| carbon film | plant leaves may form this fossil by leaving a thin layer of carbon on rock |
| trace fossils | a type of fossil that can provide clues about the activities of ancient organisms |
| paleontologist | scientist who studies fossils |
| extinct | a type of organism that no longer exists on Earth |
| relative age of a rock | its age compared to the ages of other rocks |
| 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 |
| unconformity | a gap in the geologic record where some rock layers have been lost because of erosion |
| index fossils | the fossils of organisms that were widely distributed but only lived during a short period of time |
| radioactive decay | occurs when atoms of an unstable element break down to form atoms of another element |
| half-life | the time it takes for half of the radioactive atoms in a sample of a radioactive element to decay |
| geologic time scale | a record of the life forms and geologic evewnts in Earth's history |
| vertebrates | animals with backbones |
| Pangaea | a supercontinent formed about 260 million years ago |
| fossil in amber | a type of fossil where you might find the remains of an insect preserved with little or no change |
| evolution | the process by which all the different kinds of living things have changed over long periods of time |
| absolute age of rocks | can be determined by radioactive dating |
| eras | the divisions of the geologic time scale of Paleozoic, Mesozoic, and Cenozoic |
| Cenozoic Era | Age of Mammals includes present day |
| Mesozoic Era | Age of Reptiles includes the dinosaurs |
| mammals | warm-blooded vertebrates |
| Quarternary Period | a series of ice ages occurred when Earth's climate cooled |
| carbon-14 | a radioactive element used by geologists to determine the age of organic remains |
| age of Earth | 4.6 billion years old |
| igneous rocks | rocks that radioactive dating works best with |
| amphibian | an animal that lives part of its life on land and part of its life in water |
| Precambrian Time | began with Earth forming from a mass of dust and gas |
| fossils form | when living things die adn their remains are buried by sediments |
Created by:
Mrs. Gordon
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