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Open-File Report 01-457

Lahar Hazards at Concepción Volcano, Nicaragua

By J.W. Vallance, S.P. Schilling, G. Devoli, and M.M Howell

Thumbnail of and link to report PDF (338 kB)Summary

Concepción is one of Nicaragua’s highest and most active volcanoes. The symmetrical cone occupies the northeastern half of a dumbbell shaped island called Isla Ometepa. The dormant volcano, Maderas, occupies the southwest half of the island. A narrow isthmus connects Concepción and Maderas volcanoes. Concepción volcano towers more than 1600 m above Lake Nicaragua and is within 5 to 10 km of several small towns situated on its aprons at or near the shoreline. These towns have a combined population of nearly 5,000. The volcano has frequently produced debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas. Concepción volcano has erupted more than 25 times in the last 120 years. Its first recorded activity was in AD 1883. Eruptions in the past century, most of which have originated from a small summit crater, comprise moderate explosions, ash that falls out of eruption plumes (called tephra), and occasional lava flows. Near the summit area, there are accumulations of rock that were emplaced hot (pyroclastic deposits), most of which were hot enough to stick together during deposition (a process called welding). These pyroclastic rocks are rather weak, and tend to break apart easily. The loose volcanic rock remobilizes during heavy rain to form lahars. Volcanic explosions have produced blankets of tephra that are distributed downwind, which on Isla Ometepe is mostly to the west. Older deposits at the west end of the island that are up to 1 m thick indicate larger explosive events have happened at Concepción volcano in prehistoric time. Like pyroclastic-flow deposits, loose tephra on the steep slopes of the volcano provides source material that heavy rainstorms and earthquakes can mobilize to trigger debris flow.

First posted November 20, 2013

For additional information:
Contact CVO 
Volcano Science Center, Cascades Volcano Observatory 
U.S. Geological Survey 
1300 SE Cardinal Court, Building 10, Suite 100 
Vancouver, WA 98683-9589

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Suggested citation:

Vallance, J.W., Schilling, S.P., Devoli, G., and Howell, M.M, 2001, Lahar Hazards at Concepción Volcano, Nicaragua: U.S. Geological Survey Open-File Report 01-457, 15 pp, 1 plate,



Debris Avalanches, Landslides, and Lahars

Future Landslides and Lahars at Concepción Volcano

Lahar-Hazard-Zonation Map

Hazard Forecasts and Warnings

Protecting Communities and Citizens from Lahar Hazards


Additional Suggested Reading

One plate

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