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Lahar—River of volcanic mud and debris

Fact Sheet 2018-3024

By:
ORCID iD , ORCID iD , and ORCID iD
https://doi.org/10.3133/fs20183024

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Abstract

Lahar, an Indonesian word for volcanic mudflow, is a mixture of water, mud, and volcanic rock flowing swiftly along a channel draining a volcano. Lahars can form during or after eruptions, or even during periods of inactivity. They are among the greatest threats volcanoes pose to people and property. Lahars can occur with little to no warning, and may travel great distances at high speeds, destroying or burying everything in their paths.

Lahars form in many ways. They commonly occur when eruptions melt snow and ice on snow-clad volcanoes; when rains fall on steep slopes covered with fresh volcanic ash; when crater lakes, volcano glaciers or lakes dammed by volcanic debris suddenly release water; and when volcanic landslides evolve into flowing debris. Lahars are especially likely to occur at erupting or recently active volcanoes.

Because lahars are so hazardous, U.S. Geological Survey scientists pay them close attention. They study lahar deposits and limits of inundation, model flow behavior, develop lahar-hazard maps, and work with community leaders and governmental authorities to help them understand and minimize the risks of devastating lahars.

Suggested Citation

Major, J.J., Pierson, T.C., and Vallance, J.W., 2018, Lahar—River of volcanic mud and debris: U.S. Geological Survey Fact Sheet 2018–3024, 6 p., https://doi.org/10.3133/fs20183024.

ISSN: 2327-6932 (online)

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Lahar—River of volcanic mud and debris
Series title:
Fact Sheet
Series number:
2018-3024
DOI:
10.3133/fs20183024
Year Published:
2018
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Cascades Volcano Observatory
Description:
Report: 6 p.; Video
Online Only (Y/N):
Y
Additional Online Files (Y/N):
Y