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31 True/False questions

  1. vesicleOpen holes in igneous rock formed by the preservation of bubbles in magma as the magma cools into solid rock.

          

  2. volcanoMolten rock that has flowed out onto the EarthÕs surface.

          

  3. igneous rockRock that forms when hot molten rock (magma or lava) cools and freezes solid.

          

  4. LaccolithA shallow igneous intrusion that has a blister-like shape.

          

  5. glassy igneous rockIgneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix.

          

  6. obsidianA tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

          

  7. batholithA shallow igneous intrusion that has a blister-like shape.

          

  8. fragmental igneous rockIgneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix.

          

  9. GeothermA pyroclastic igneous rock composed of volcanic ash and fragmented pumice, formed when accumulations of the debris cement together.

          

  10. StopingA glassy mafic igneous rock containing abundant air-filled holes.

          

  11. pumiceA tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

          

  12. pyroclastic rockRock made from fragments blown out of a volcano during an explosion that were then packed or welded together.

          

  13. sillA tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

          

  14. PegmatiteA glassy igneous rock that forms from felsic frothy lava and contains abundant (over 50%) pore space.

          

  15. scoriaA glassy mafic igneous rock containing abundant air-filled holes.

          

  16. fractional crystallizationThe process by which magma becomes progressively more silicic as it cools, because early-formed crystals settle out.

          

  17. plutonAn irregular or blob-shaped intrusion; can range in size from tens of meters across to tens of kilometers across.

          

  18. TuffA tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

          

  19. crystalline igneous rockA rock that solidifies from a melt and consists of interlocking crystals.

          

  20. extrusive igneous rockRock formed by the freezing of magma underground.

          

  21. intrusive igneous rockRock that forms by the freezing of lava above ground, after it flows or explodes out (extrudes) onto the surface and comes into contact with the atmosphere or ocean.

          

  22. xenolithA vast composite, intrusive, igneous rock body up to several hundred kilometers long and 100 km wide, formed by the intrusion of numerous plutons in the same region.

          

  23. lavaMolten rock that has flowed out onto the EarthÕs surface.

          

  24. assimilationAn igneous rock consisting of a solid mass of volcanic glass.

          

  25. partial meltingThe process of magma contamination in which blocks of wall rock fall into a magma chamber and dissolve.

          

  26. MagmaMolten rock beneath the EarthÕs surface.

          

  27. volcanic ashTiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.

          

  28. volcanic brecciasTiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.

          

  29. dikeA nearly horizontal table-top-shaped tabular intrusion that occurs between the layers of country rock.

          

  30. lava flowSheets or mounds of lava that flow onto the ground surface or sea floor in molten form and then solidify.

          

  31. Bowen's reaction seriesA rock composed of angular chunks of volcanic debris that have been cemented together.