San Cristobal is a stratovolcano located in Nicaragua and is a basaltic cone with a flattened top. This cone is built of alternating layers of lava and tephra. The volcano would never have grown as large as it is without these lava layers to support the slopes and keep the tephra from eroding. It is the youngest volcano in the San Cristobal complex, which consists of five volcanoes. It is also the most active of the five. It has erupted eight times, the latest being in 1977. 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. A single vent leads 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.
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.
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