Geologic Background:
Cerro Negro is a basaltic cinder cone that has
erupted repeatedly since its birth in 1850. It is located
along a SE-NW-trending volcanic lineament that includes
numerous cones and craters including:
- Malpaisillo: maar
- Cerro Negro: cinder cone
- Las Pilas:
composite cone
- Ojo de Agua: cinder cone
- Asososca: cinder cone
- Cerro Los Tacatices: cinder cone
Historic Activity:
- Following a major explosive eruption in 1971, Cerro
Negro was quiet until an April 1992 eruption produced a
Plinian column 7.5 km high, which deposited ash in
León (20 km WSW), and forced the evacuation of
28,000 people.
- A significant eruption in November-December 1995
followed almost six months of unrest and minor eruptive
activity. That eruption built a new cone, lava dome, and
lava flows within the summit crater, sent lava flows 1.5
km down the N flank, and deposited ash over at least 200
square kilometers.
Recent Activity:
- Strong seismic activity began the night of Aug 4-5,
1999 and an eruption began late on the morning of Aug. 5.
Eruption had ended by Aug. 7.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 5, No. 2 to V. 14,
No. 2)
- Global Volcanism Network (V. 16, No. 2 to V. 25, No.
9).
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