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18weekassessment
| Term | Definition |
|---|---|
| igneous rock | formed when magma cools and hardens |
| magma | magma forms when rock melts |
| crystalline | full of crystals |
| intrusive | magma cools below ground; larger crystals |
| extrusive | magma cools above ground |
| coarse-grained | generally light colored with dark crystals spread throughout |
| fine-grained | small grains invisible to the human eye |
| porphyritic | rock with a mix of large and small crystals; granite is an example |
| glassy | few or no crystals; obsidian is an example |
| vesicular | many holes inside and outside; pumice is an example |
| felsic | rich in minerals that form feldspar and quartz |
| mafic | contains a group of dark colored minerals |
| compaction | sediment progressively loses its porosity due to the effects of loading |
| chemical sedimentary rock | formed when minerals, dissolved in water, begin to precipitate out of solution and deposit at the base of the water body |
| organic sedimentary rock | contains significant amounts of organic carbon |
| clastic sedimentary rock | form by weathering processes which break down rocks into pebble, sand, or clay particles by exposure to wind, ice, and water |
| sorting | the tendency for currents of air or water to separate sediments according to size |
| cementation | hardening and welding of clastic sediments by the precipitation of mineral in the pore spaces |
| angularity | used to describe the shape of the corners on a particle of sediment |
| stratification | the layering of rocks |
| cross-bedding | horizontal units that are internally composed of inclined layers |
| ripple marks | sedimentary structures and indicate agitation by water or wind |
| mud cracks | when muddy deposits dry and shrink |
| concretions | lumps of rock that have a composition that is different from that of the main body |