Report on Masaya (Nicaragua) — 10 August-16 August 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 August-16 August 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Masaya (Nicaragua). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 August-16 August 2016. Smithsonian Institution and US Geological Survey.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
Based on analysis of satellite imagery, the Washington VAAC reported that on 15 August a possible ash plume from Masaya rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted NW. Elevated seismicity and a thermal anomaly detected in satellite images indicated increased activity. In a report posted later that day the Washington VAAC noted that the webcam recorded minor ash emissions.
Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.