Report on Concepcion (Nicaragua) — 20 May-26 May 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 May-26 May 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Concepcion (Nicaragua). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 20 May-26 May 2015. Smithsonian Institution and US Geological Survey.
11.538°N, 85.622°W; summit elev. 1700 m
All times are local (unless otherwise noted)
According to a 6 May news article, activity at Concepción had increased about three weeks prior and was characterized by fluctuating levels of seismicity and gas explosions. In a 8 May statement, INETER noted that seismic activity and gas explosions at Concepción had decreased since the day before; 15 gas explosions has been detected in a 24-hour period. By 24 May there had been a total of 987 gas explosions detected by the network since an unspecified date of increased activity.
Geologic Background. 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.