Report on Masaya (Nicaragua) — 4 May-10 May 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 May-10 May 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, 4 May-10 May 2016. Smithsonian Institution and US Geological Survey.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
INETER reported that between 1700 and 2400 on 3 May volcanic tremor at Masaya increased; RSAM values spiked at 1,000 units and then dropped to 250. Gas emissions at Santiago crater were at low-to-moderate levels, and the lava lake continued to strongly circulate. On 5 May RSAM values fluctuated between 250 and 500 units, which are low-to-moderate values.
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.