Report on Masaya (Nicaragua) — 24 July-30 July 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
24 July-30 July 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Masaya (Nicaragua). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 24 July-30 July 2019. Smithsonian Institution and US Geological Survey.
11.985°N, 86.165°W; summit elev. 594 m
All times are local (unless otherwise noted)
INETER reported that at 1655 on 21 July a small explosion at Masaya’s Santiago Crater produced a gas-and-ash plume that drifted NW and W. A thin layer of ash was deposited near the volcano and in surrounding communities downwind, including San Ignacio, Panamá, and Arenal. During field visits during 21-22 July, INETER volcanologists confirmed that the emissions had originated from a vent on the crater floor.
Geological Summary. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself 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 Nindirí and Masaya cones, 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 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. 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 have caused health hazards and crop damage.