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Unit 07 24-25
Geologic History
| Term | Definition |
|---|---|
| absolute dating | the process of measuring the specific age of an object or event in terms of years, a time range, or actual date |
| catastrophism | The idea that Earth's history has been characterized by a series of extreme, rapid, worldwide events. |
| continental drift | the theory that the earth's continents shift their positions because of currents in the molten magma of the earth's mantle. |
| eon | the longest division of time in the geologic time scale |
| era | the second-longest division in the geologic time scale, measured in tens- to hundreds-of-millions of years |
| index fossils | fossils of organisms belonging to species that existed in large numbers for a relatively short amount of geologic time; used to date the rocks in which they are found |
| mid-ocean ridge | an oceanic rift zone that consists of long mountain chains with a central rift valley; divergent boundary |
| period | a unit or division of geologic time that is part of an era |
| relative dating | the process of comparing objects or events to determine which are younger or older, without knowing their specific ages |
| seafloor spreading | the process by which new oceanic lithosphere forms at mid-ocean ridges as tectonic plates pull away from each other |
| superposition | the ordering of sedimentary layers of rock with the oldest on the bottom and the youngest on top |
| uniformitarianism | the principle that throughout Earth's history, slow geologic processes (such as weathering and erosion) have been occurring in the same manner and at the same rates, and that these processes have been primarily responsible for shaping Earth's surface |
| fossil | the remains or trace of a living animal or plant from a long time ago. Fossils are found embedded in earth or rock. |
| strata | a horizontal layer, esp. one of several parallel layers in a pile. Seen in a cross section of rock. |
| Pangaea | in plate tectonics, the single land mass that was composed of all the land on Earth until it began breaking into smaller continents 300 million years ago. |
| plate tectonics | theory that scientists use to explain the movement of continents, eruption of volcanoes, and changes or events in the earth's geology. Says that the earth's crust is made up of sections that move around constantly because they float on melted rock. |
| ocean trench | a long, narrow part of the ocean floor that is much deeper than the area on either side of it. A trench is like a deep dent or cut in the floor of the ocean. |
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LMS 7 Sci
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