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[lah-hahr] /ˈlɑ hɑr/
noun, Geology
a landslide of wet volcanic debris on the side of a volcano.
the deposit left by such a landslide.
1925-30; < Javanese: lahar, lava Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for lahar
  • The lahar was terrifyingly high and steaming hot, they reported.
  • Wood fragments in two channel-fill deposits gave ages similar to lahar deposits upstream.
  • Dark streaks on pyroclastic-flow deposits are lahar deposits generated by rains.
  • It is already mixed with rock debris eroded from the crater walls, and this debris would augment the formation of a lahar.
  • The lahar and flood destroyed six mostly not-yet-occupied summer ranch houses.
  • Deposits described herein are part of a dynamic system involving large ignimbrite sheets and lahar conveyance channels.
British Dictionary definitions for lahar


a landslide of volcanic debris mixed with water down the sides of a volcano, usually precipitated by heavy rainfall
Word Origin
C20: from Javanese: lava
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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lahar in Science
  1. A wet mass of volcanic fragments flowing rapidly downhill. Lahars usually contain ash, breccia, and boulders mixed with rainwater or with river or lake water displaced by the lava flow associated with the volcano.

  2. The deposit produced by such a flowing mass.

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

mudflow of volcanic material. Lahars may carry all sizes of material from ash to large boulders and produce deposits of volcanic conglomerate. Lahars may be the result of heavy rain on loose ash material such as deposits of nuees ardentes (dense clouds of gases charged with incandescent dust, discharging volcanic sand in avalanche fashion); or they may result from the mixing of debris with river water, the flooding of ash by snow or ice melted by an eruption, or the emptying of crater lakes onto loose material. A variation is the hot lahar ordinarily produced by the heating of the crater lake water by the quiet upwelling of lava or an explosion. Lahars move downslope at very high speeds and may extend for tens of miles. A lahar deposit usually has a hummocky or hilly surface. They often cause much death and destruction, as at Herculaneum during the eruption of Vesuvius in AD 79.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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