What do a.m. and p.m. stand for?


[met-uh-mawr-fiz-uh m] /ˌmɛt əˈmɔr fɪz əm/
Geology. a change in the structure or constitution of a rock due to natural agencies, as pressure and heat, especially when the rock becomes harder and more completely crystalline.
Archaic. metamorphosis.
Origin of metamorphism
1835-45; meta- + -morphism Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for metamorphism
  • metamorphism is a complex process with a number of simultaneously interacting and related components.
  • Another type of metamorphism, contact metamorphism, occurs when hot igneous rock intrudes into some pre-existing rock.
  • Two of the common types are: regional metamorphism and contact metamorphism.
  • Low-temperature scanning electron microscopy of snow crystal metamorphism in winter snow covers.
  • metamorphism generally demolishes fossils beyond recognition.
  • metamorphism will change the rock's mineralogic or textural features.
  • The process of metamorphism does not melt the rocks, but instead transforms them into denser, more compact rocks.
  • Volcanic eruptions and metamorphism release gases into the atmosphere.
British Dictionary definitions for metamorphism


the process by which metamorphic rocks are formed
a variant of metamorphosis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for metamorphism

1837, from metamorphic + -ism.

Online Etymology Dictionary, © 2010 Douglas Harper
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metamorphism in Science
The process by which rocks are changed in composition, texture, or structure by extreme heat and pressure. ◇ In prograde metamorphism metamorphic rocks that were formed under low pressure and temperature conditions undergo a second metamorphic event in which they are exposed to higher pressures and temperatures. ◇ In retrograde metamorphism metamorphic rocks that were formed under high pressure and temperature conditions undergo a second metamorphic event in which they are exposed to lower pressures and temperatures. See more at contact metamorphism, regional metamorphism.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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