is the northern-most historically active volcano in South America (4.9N,
75.3W). Because of the high elevation of the summit (17,453 feet, 5,321
m), the volcano is capped by a large volume of snow and ice. In 1595 and
1845 summit eruptions melted snow and ice and produced mudflows that traveled
tens of miles from the volcano. These mudflows were confined to the valleys
that drain the volcano. The 1985 eruption of Ruiz, although only moderately
explosive, produced mudflows which reached the town of Armero and killed
more than 23,000 people. This eruption of Ruiz was the second mostly deadly
of the century (Mount Pelee in Martinique was first, killing 29,000 people
in its 1902 eruption). This photograph shows the volcano in the early stages
of the 1985 eruption. Photograph courtesy of U. S. Geological Survey.
Armero, Colombia, destroyed
by lahar on November 13, 1985.More than 23,000 people were killed in Armero
when lahars (volcanic debris flows) swept down from the erupting Nevado
del Ruiz volcano. When the volcano became restless in 1984, no team of
volcanologists existed that could rush to the scene of such an emergency.
However, less than a year later, the U.S. Geological Survey organized a
team and a portable volcano observatory that could be quickly dispatched
to an awakening volcano anywhere in the world. Photo by R.J. Janda, courtesy
of USGS Cascades Volcano Observatory.
of the U.S. Geological Survey.