Last Updated: March 20, 2006
|San Cristobal is not the tallest volcano in Nicaragua, but it is the most massive. It is locally known as El Viejo, which translates as "the old one."
San Cristobal is a stratovolcano that has a basaltic cone with a flattened top. This cone is built of alternating layers of lava and tephra. These alternating lava layers allowed the volcano to grow large by keeping the tephra layers from eroding. The symmetrical cone, San Cristobal (also known as El Viejo) is the highest peak of the Maribios Range, and is capped by a 500 x 600 meter wide crater. It is the youngest and most active cone in the five crater complex. The communities of El Viejo and Chinandega are located near San Cristobal, but are only threatened by ashfall.
Lava from San Cristobal is aa. It is uniformly basaltic with many phenocrysts. These lavas are also very rich in vesicles. Lava flows from San Cristobal are usually between 10 and 13 km in length with a single vent leading to each flow. Several small cinder cones have also formed at these vents at the base of the volcano.
San Cristobal spent almost three centuries in a dormant state between 1685 and 1971. In 1971, San Cristobal had 3 craters. These began to sink with renewed activity and had gone down almost 90 meters after eruptions in late 1976. The latest eruption was in 2005.
|The San Cristobal volcanic complex consists of five principal edifices. The youngest cone, the namesake San Cristobal is the highest peak of the Marrabios Range. Several radial flank craters occur along a N-S line on the outer north flank of 1745-m-high San Cristobal. Historical activity, consisting of small-to-moderate explosive eruptions, has been reported since the 16th century. The SW crater rim (left) rises 140 m above the NE rim because prevailing trade winds distribute tephra to the SW.
For more information about Lahar hazards at San Cristobal, see:
J.W. Vallance, S.P. Schilling, G. Devoli, M.E. Reid, M.M. Howell, and D.L. Brien, 2004, Lahar Hazards at Casita and San Cristobal Volcanoes, Nicaragua: USGS Open-File Report 01-468
Sources of Information:
Some information provided courtesy of the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program.
Hazlett, Richard, "Geology and Hazards of the San Cristobal Volcanic Complex," M.S. Thesis, Dartmouth College, Hanover, NH, 212pp., June 1977.
Simkin, Tom and Siebert, Lee, "Volcanoes of the World," Geoscience Press, Tuscon, AZ, 349 pp., 1994.