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Report on Concepcion (Nicaragua) — 3 August-9 August 2005


Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
3 August-9 August 2005
Managing Editor: Gari Mayberry

Please cite this report as:

Global Volcanism Program, 2005. Report on Concepcion (Nicaragua). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 August-9 August 2005. Smithsonian Institution and US Geological Survey.

Weekly Report (3 August-9 August 2005)



11.538°N, 85.622°W; summit elev. 1700 m

All times are local (unless otherwise noted)

According to INETER by 0400 on 3 August, 38 earthquakes had occurred on the Island of Ometepe. The strongest earthquake (ML 5.6) occurred at 0603 and was felt in the surrounding region. The epicenter was estimated to be underneath Lake Nicaragua, SE of the Island of Ometepe, ~10-15 km SE of Volcán Maderas. This earthquake did not cause significant damage because the epicenter was not close to populated areas. The magnitude of this event was comparable to the 1972 earthquake in Managua.

Geological Summary. Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the N flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)