GLACIAR
511
Event description
On May 31, 1970 the most catastrophic known avalanche
in history descended from Nevados Huascaran,
the highest peak in the Peruvian Andes. The avalanche caused about 18`000 casaulties. The avalanche was triggered at 3:23 PM by a
great earthquake (M=7.7). The avalanche originated from a partially overhanging
cliff at 5400-6500 m elevation, where the fractured granitic
rock of the peak was covered by a 30-m-thick glacier. The avalanche had a volume
of ~ 50-100 million cubic meters and traveled 16 km
to Rio Santa with a vertical drop of 4 km.
Damage
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The aluvion buried the city
of
Data source
- Lliboutry, L., Arnao, B. M., Pautre, A., Schneider, B. (1977): Glaciological problems set by the contol of dangerous lakes in Cordillera Blanca,
- http://www.soest.hawaii.edu/martel/Courses/GG454/GG454_Lec_20.pdf
Remarks
Mapping after the 1970 event revealed deposits from a
substantially larger pre-Columbian (before 1492) avalanche that might have
attained average speeds of 315-355 km/hr.