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Trap rock
Trap rock, also known as either trapp or trap, is any dark-colored, fine-grained, non-granitic intrusive or extrusive igneous rock. Types of trap rock include basalt, peridotite, diabase, and gabbro.[1] Trap is also used to refer to flood (plateau) basalts, such as the Deccan Traps and Siberian Traps.[2] The erosion of trap rock created by the stacking of successive lava flows often creates a distinct stairstep landscape from which the term trap was derived from the Swedish word trappa, which means "stairs".[1]
The slow cooling of magma either as a sill or as a thick lava flow sometimes creates systematic vertical fractures within the resulting layer of trap rock. These fractures often form rock columns that are typically hexagonal, but also four- to eight-sided.[3][4]
- ^ a b Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.) American Geological Institute, Alexandria, Virginia. 779 pp. ISBN 978-0-922152-76-6
- ^ Le Maitre, R. W., ed. (2002) Igneous Rocks: A Classification and Glossary of Terminology. Cambridge University Press, New York. 236 pp. ISBN 978-0-521-66215-4
- ^ Muller, G. (1998) "Experimental simulation of basalt columns". Journal of Volcanology and Geothermal Research. vol. 86, no. 1–4, pp. 93–96
- ^ Spry, A. (1962). "The origin of columnar jointing, particularly in basalt flows". Journal of the Geological Society of Australia. Vol. 5, pp. 191–216.
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