Geologic Background:
Concepción is one of Nicaragua's highest
and most active volcanoes. The symmetrical 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. Concepción's
steep-walled summit crater is 250 m deep and has a
still-higher western rim. N-S-trending fractures on the
flanks of the volcano have been the focus for 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. The volcano was
constructed above lake sediments and the modern cone grew
above a largely buried caldera. Frequent explosive
eruptions during the past half century have increased the
height of the summit significantly above that shown on
topographic maps and have kept the upper part of the
volcano unvegetated.
Historic Activity:
- Concepcion has had frequent moderate explosive
eruptions since the first certain historical eruption in
1883. Twenty-four eruptions have been reported since
1883.
Recent Activity:
- A tephra eruption in December 1984 ejected blocks and
ash that damaged crops, and ash emissions were reported
between late 1985 and April 1986.
- Fumarolic activity reported in 1997.
- Seismic tremor began on Dec. 23, 1999 and low level
eruptive activity was confirmed on Dec. 28. Seismicity
and volcanic activity ended on Dec. 30.
- Low levels of seismicity through April 2000.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 2, No. 4 to V. 14,
No. 4)
- Global Volcanism Network (V. 16, No. 2 to V. 25, No.
9).
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