Natural disasters in the Cordillera
Blanca, Peru

Why human sacrificies in mountains?
• Archaeological sites and mummies have been found in the
Andes at altitudes up to 6,700m
• Incas constructed the sites in the 15 th century to appease the mountain gods

Natural disasters in the Cordillera
Blanca, Peru
• Major tectonic faults that are active
• Marked glacierization
• Geologically young, steep mountains
• Pro-glacial lakes
• Immediate vicinity of human settlements

ALPAMAYO

ARTESONRAJU

• Large snow year
• 50 degree F increase in temp over a few minutes
• Caused avalanche
• 4,000 fatalities
• Yungay protected by ridge

• Triggered by 7.7 magnitude earthquake
• Rock face failure
• Incorporated 30 meters of snow and ice!
• Moraines confined flow initially
• Accelerated over a distance of 2.4 km
• Became airborne at change of slope

Church before 1970 avalanche. Note palm trees in foreground.

Many years after the avalanche. Note palm trees survived.

Yungay is now completely abandoned. Cemetery has a monument to the dead.

Guiness book of records as the most deaths ever from an avalanche

• Trigger was a large earthquake; 7.7
• Caused avalanche with rock slide
• 20,000 fatalities
• Yungay destroyed

• Moraine damming the proglacial Lake Palca
(cocha = lake:
Palcacocha) broke
• Resulting flood killed
6,000 people in
Huaraz

HUARAZ, circa 1970

1970 Earthquake that caused the Huascaran disaster killed about 40,000 people in
Huaraz.
Streets of Huaraz after the
1970 Earthquake.
Adobe houses collapsed, killing people inside.

May 3, 2003: “NASA feels the heat as glacier pictures cause unrest in Peru”, according to Nature
HUARAZ CASE STUDIES

QuickTime™ and a
decompressor are needed to see this picture.

• A chunk of glacier was threatening to fall into an Andean lake and cause major flooding in a Peruvian city of 60,000. A fissure has appeared in the glacier that feeds the Lake Palcacocha near the city of
Huaraz, 270 km north of Lima.

• If the piece breaks off, ensuing floods would take
15 minutes to reach the city. In 1941, the lake overflowed and caused massive destruction, killing 7,000 people.

• The city can be seen in the left-center part of the image. Lake Palcacocha is in the upper right corner of the image at the head of a valley, below the snow and glacier cap. The Advanced
Spaceborne Thermal Emission and Reflection
Radiometer (ASTER) instrument, aboard NASA’s
Terra satellite, is being tasked to obtain current images of the glacier to help monitor the situation.

ASTER image,
2001
Fissure
NASA interprets as huge crevasse

ASTER image,
2003
Fissure
NASA believes glacial release into the lake is imminent

Palcacocha, historical photograph

Rock band from glacial retreat, not crevasse.
Palcacocha

Located above Yungay
Potential Pro-glacier flood

1940’s flood from glacier failure

Huge rock glacier dammed lake.
Could collapse at any time.

Installed drainage tunnel
Lowered lake level

• 1962 Huascaran avalanche killed 4,000
• 1970 Huascaran avalanche killed 20,000
• 1941 proglacial lake outburst from
Palcacocha killed 6,000 in Huaraz
• Lago Paron could have an outburst at any time from (a) collapse of rock glacier damn;
(b) glacial ice fall into lake; c) combination of both

Summary: causes
• Major tectonic faults that are active
• Marked glacierization
• Geologically young, steep mountains
• Pro-glacial lakes
• Immediate vicinity of human settlements