Cerro Negro, Nicaragua
- November 21, 1999
- The following is an update on the
Cerro Negro Volcano contributed by Mr. Brittain Hill.
- There was no eruption at Cerro Negro
in November, 1998. While flying up to the Casitas area to evaluate the
damage from the large landslide, scientists from INETER observed lots
of steam emanating from the Cerro Negro cone and the 1995 lavas. This
was erroneously reported as the eruption. When they visited the site
the next day, they confirmed that the steam was nothing more than inflitration
of the 2+ m of rainfall into the still hot 1995 deposits. There was
no seismicity and no new deposits, in 1998. I've spoken with the INETER
geologists and visited Cerro Negro in March 1999 and can confirm there
were no new deposits on the 1995 falls and lavas.
- We were at Cerro Negro immediately after
the August 5-7 eruption and can confirm that some houses were damaged
in Rota by relatively large (M4.9 and 4.2) earthquakes that preceeded
the eruption by 4-12 hours. There was, however, no damage from lavas
or tephra-falls. Lavas were restricted to within 100 m of the new
which opened adjacent to Christo Rey on the S base of the main cone,
and maximum distance for incandescent ballistics were about 300 m. Tephra
falls >1-cm-thick were restricted to <2 km of the new vents. We
will present this at the Fall AGU Meeting, and show how the eruption
was successfully forecast using time-volume relationships.
August 9, 1999
- On 6 August, 60 homes were damaged by
a rock and lava flow from the Cerro Negro Volcano. 17 homes were destroyed
in an earthquake related to the eruption which began on 5 August. Lava
and ash are erupting from three new openings in the volcano. Government
officials declared a state of maximum alert. Approximately 2,000 people
have been evacuated to shelters.
- August 6, 1999
- On 5 August, the Cerro Negro Volcano
erupted. Volcanologists measured lava temperatures of up to 1,500 degrees.
The activity originated in four new vents outside of the main crater.
Lava fountains rose to 300 m in height. On the evening of 4 August,
earthquakes with magnitudes up to 4.8 were felt in all of Northwestern
Nicaragua.Civil Defense officers began preparations for an eventual
evacuation of nearby villages.
- November 6, 1998
- The continuing eruption of Cerro Negro
has forced the evacuation of the village of Rota. Up to 3500 people
in several other villages could be evacuated in the next few days as
lava flows continue to move down the north flank of the volcano.
- November 3, 1998
- Cerro Negro volcano began erupting on
November 3, just one week after 2,000 people were killed by a mudslide
originating from neighboring Casitas Volcano. Lava flows and ash covered
about 25% of Cerro Negro's north flank soon after the eruption began.
These flows appeared to have reached the base of the volcano. There
were no reports of damage or casualties.
- View from 2.3 miles (3.6 km) northwest
of Cerro Negro on 3:00 p.m. on November 30, 1995. Column is about 1
mile (1.5 km) high and blown to west-northwest (right) by prevailing
strong winds. Ash accumulates in Leon (12 miles (20 km) downwind under
cloud) at about 2 mm per day. Diffuse lapilli-fall under proximal cloud
to about 3 miles (5 km).
- Cerro Negro, a cinder cone, reawakened
late in the morning of November 19, 1995. Initial activity was Strombolian
in character. Detailed observations began late on November 21. An almost
constant fountain of material threw bombs and small amounts of ash 1,000-1,300
feet (300-400 m) above the lip of the crater. Some bombs were very large,
measuring several feet (meters) across. A new cone was growing and filling
the older crater that was built by an eruption in 1992. A small lava
dome was growing adjacent to the new cone. On the morning of November
22, a series of strong explosions ejected material that fell on the
lower slopes of the cone. By that evening the new cone had overgrown
the side of the 1992 crater and material was spilling down the slope.
Slow moving lava flows appeared over the edge of the old crater and
material from the front of the flow rolled to the base of the main cone.
|| View from 2,000 feet (600 m) south-southeast
of main vent on 9:50 a.m. on December 1, 1995, last full day of
eruption. Note dense black-to-grey convective ash column and fresh
fallout on western (left) sector of cone. South rim is morphology
from 1992 eruption; no significant growth in 1995 on south cone
- The eruption at Cerro Negro continued
on November 25 and 26. Observers reported that at times massive bombs
were thrown 2,000 feet (600 m) into the air. At others times, strong
explosions sent up dense ash clouds. Some ash eruptions lasted several
hours. The new cone continued to grow and was about 30-50 m below the
summit of the old crater. A lava flow advanced about 1,600 feet (500m)
to the west but stopped early in the morning on November 26. An unusual
spine-like lava dome jutted out on the northern edge of the crater.
The dome was about 300 feet (100m) wide and 100 feet (40m) high. Blocks
were continually spalling off the dome. The dome produced three small
lava flows that extended to the base of the cone and were advancing
slowly. Two flows moved slowly to the north and reached about 0.6 to
1 mile (1 to 1.5 km) from the volcano. Earthquake tremor was recorded
during the entire period.
- View from 1 km north-northwest of Cerro
Negro on December 3, 1995. 99% of lava in view is new, as are the levees
and ramps on the north-northeast (left) sector of the cone flank. The
upper contact of the ramps represents the 1992 cone rim. About 150 feet
(50 m) of height was added to the cone in 1995, with about 2/3 of the
1992 crater infilled with new scoria and lava. Lavas extend to about
1 mile (1.5 km) north of the north base of cone.
- On December 4, the Department of Humanitarian
Affairs of the United Nations issued a
- Situation Report concerning Cerro Negro.
They requested international assistance for basic relief supplies and
food items. They noted that the eruptions has affected 12,000 people
and 6,000 people have been evacuated.
- Also on December 4, the Associated Press
released a story that Cerro Negro stopped erupting on December 3.