Report on San Cristobal (Nicaragua) — 5 September-11 September 2012
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 5 September-11 September 2012
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2012. Report on San Cristobal (Nicaragua) (Sennert, S, ed.). Weekly Volcanic Activity Report, 5 September-11 September 2012. Smithsonian Institution and US Geological Survey.
12.702°N, 87.004°W; summit elev. 1745 m
All times are local (unless otherwise noted)
INETER reported that on 8 September three explosions from San Cristóbal produced ash-and-gas plumes that rose 1.5 km above the crater and drifted 9 km/hr NW. Ashfall was reported in El Viejo (18 km WSW), El Chonco, and Ranchería. Sporadic explosions later that day generated ash plumes that rose 1.5-5 km and drifted 50 km WNW. Ash fell in an area covering 2,438 square kilometers, including the communities of El Viejo, La Grecia, La Joya, Santa Catalina, El Piloto, Las Banderas, Las Rojas, Carlos Fonseca, Jiquilillo, Mechapa, and Cosiguina. Ashfall was 5 cm thick in areas near the crater and up to 3 mm thick in more distant places. Sulfur dioxide emissions were 3,221 tons per day, well above the normal range of 550 to 700 tons per day. A resident near the volcano reported landslides and falling rocks in the N part of the crater. Incandescent rocks fell in areas NW, causing burns on livestock. Residents in Versalles Arriba, near the crater, reported seeing a fissure. According to a news article, officials evacuated about 3,000 people. SINAPRED reported that airplanes were diverted around San Cristóbal to other airways.
Geological Summary. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.