78331
Description
Flashcards by siobhan.quirk, updated more than 1 year ago
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Created by siobhan.quirk
over 12 years ago
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| Question | Answer |
| Define continents | situated on crust with an average thickness of 33km and a mean composition close to that of granite |
| Define seismic tomography | is a computer imaging technique based on seismic wave velocities |
| Define diapir | low density, buoyant material rising upwards in the same way as hot wax does in a lava lamp |
| Define mantle plume | a stationary area of high heat flow in the mantle, which rises from great depths and produces magma that feeds hot spot volcanoes |
| Define hot spot | a volcano within a plate, which is the surface expression of a mantle plume |
| Define oceanic plate | has no continental material |
| Define continental plate | carries a continent but will also have oceanic crust |
| Define lithosphere | divided into plates, carried by the moving underlying asthenosphere. |
| Define lithosphere plate | a layer of thecrust and upper mantle in which the rocks are rigid and brittle |
| Define depth of focus | earthquakes are classified by their depth at which the stress acts (see 1.3.5) |
| Define ocean basins | are situated on crust with an average thickness of only 7km, formed maninly of rocks with a basaltic composition |
| Define continental drift | the large sclae horizontal movement of continents during geological time |
| Define clastics | sediments made up of fragments of pre-existing rock |
| Define planktonic | organisms that float in sea water |
| Define pelagic | is applied to organisms living in, and sediment deposited from, the main body of sea water |
| Define mafic | igneous rocks with 45-52% silica, such as basalt |
| Define gravimeter | can be towed behind a ship to measure changes in gravity. (see notes - 1.3.2) |
| Define magnetometer | is towed behind a ship to measure changes is magnetism. It can detect the strength and direction of the magentic field |
| Define apparent polar wandering curve | is depicted by a line on a map, which joins up the apparent positions of the magentic north pole over time |
| Define evaporites | minerals fomed by the evaporation of saline water for example: calcite, halite, gypsum, k-salts |
| Define tillites | ancient glacial deposits preserved within a rock sequence |
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