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Open-File Report 01-395

Lahar-Hazard Zonation for San Miguel Volcano, El Salvador

By J.J. Major, S.P. Schilling, C.R Pullinger, C.D. Escobar, C.A. Chesner, and M.M. Howell

Thumbnail of and link to report PDF (389 kB)Summary

San Miguel volcano, also known as Chaparrastique, is one of many volcanoes along the volcanic arc in El Salvador. The volcano, located in the eastern part of the country, rises to an altitude of about 2130 meters and towers above the communities of San Miguel, El Transito, San Rafael Oriente, and San Jorge. In addition to the larger communities that surround the volcano, several smaller communities and coffee plantations are located on or around the flanks of the volcano, and the PanAmerican and coastal highways cross the lowermost northern and southern flanks of the volcano. The population density around San Miguel volcano coupled with the proximity of major transportation routes increases the risk that even small volcano-related events, like landslides or eruptions, may have significant impact on people and infrastructure.

San Miguel volcano is one of the most active volcanoes in El Salvador; it has erupted at least 29 times since 1699. Historical eruptions of the volcano consisted mainly of relatively quiescent emplacement of lava flows or minor explosions that generated modest tephra falls (erupted fragments of microscopic ash to meter sized blocks that are dispersed into the atmosphere and fall to the ground). Little is known, however, about prehistoric eruptions of the volcano. Chemical analyses of prehistoric lava flows and thin tephra falls from San Miguel volcano indicate that the volcano is composed dominantly of basalt (rock having silica content <53%), similar to the lava erupted by Hawaiian volcanoes. The chemical composition of eruptive products and the lack of evidence of large cataclysmic eruptions suggests that prehistoric eruptions probably were similar in nature to the historical eruptions. Unlike San Salvador and San Vicente volcanoes, San Miguel volcano does not appear to have had a history of violent explosive eruptions.

First posted November 20, 2013

For additional information:
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U.S. Geological Survey 
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Vancouver, WA 98683-9589

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Suggested citation:

Major, J.J., Schilling, S.P., Pullinger, C.R., Escobar, C.D., Chesner, C.A., and Howell, M.M., 2001, Lahar-Hazard Zonation for San Miguel Volcano, El Salvador: U.S. Geological Survey Open-File Report 01-395, 16 pp., 1 plate, https://pubs.usgs.gov/of/2001/0395/.

 



Contents

Introduction

Debris Avalanche, Landslide, and Lahar

Future Landslides and Lahars at San Miguel Volcano

Lahar-Hazard-Zonation Map

Lahar Hazard Forecasts and Warnings

Protecting Communities and Citizens from Lahar Hazards

References

Additional Suggested Reading

One plate


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