Mount St. Helens (01:29)
Most landslides occur in Asia, but those with high mortality rates occur in the Americas. The greatest recorded event took place in 1980 on a Washington volcano—reshaping the landscape. Only 57 people died due to a successful evacuation.
Human Landslide Factors (01:35)
A Cairo cliff face collapsed onto a slum, killing 100. Families blamed authorities for destabilizing the plateau through construction. In Chittagong, Bangladesh, illegal deforestation weakened hillsides, leading to a flash flood burying a poor area in mud.
Landslide Definition (02:41)
Landslides are uncontrollable downhill flows of mud, rock, and debris traveling up to 200 mph. Soil creeps are slower moving. Landslides can impede construction; at the Three Gorges Dam, water pressure collapsed reservoir banks and triggered a tsunami.
Rock Slides and Slumps (02:40)
Rock falls usually start after prolonged rains, and are unexpected. Slumps occur when rock or earth slabs lose adhesion and slide down hills. Debris flows occur after rains destabilize earth, and have caused destruction in South and Central America. Peru suffered devastating events in 1962 and 1970.
Aberfan Disaster (02:03)
In South Wales in October 1966, 500,000 tons of coal waste broke free of a slag heap, burying a village school without warning.
Search and Rescue Efforts (02:51)
Local police, miners and volunteers were only able to recover a few children alive after the Aberfan landslide.
Community in Mourning (02:13)
Aberfan residents grieved for victims of the 1966 landslide. Over 140 villagers died in total, mostly children. Many blamed the state run mining company for negligence.
Aferban Tribunal (04:55)
Mining waste material was piled in slag heaps above the village school; springs destabilized the debris over time and led to the 1966 landslide. An inquiry found NCB Chairman Lord Robens’ negligence responsible for the disaster. Locals built a memorial at the school site.
Armero Disaster (03:23)
In November 1985, the Navaro del Ruiz volcano erupted, setting off landslides that buried a town of 20,000 in Tolima, Colombia. Scientists had detected eruption signs and published a landslide map but authorities dismissed them as being alarmist.
Armero Landslide (03:22)
Colombian authorities failed to evacuate Armero. On November 13, Navaro del Ruiz erupted, melting snow and ice that streamed into river valleys. Chinchiná and Armero were engulfed in a mud lake.
Armero Rescue Efforts (02:04)
The Colombian government's failure to warn and evacuate Armero and Chinchiná resulted in 23,000 of 28,000 residents being buried in the landslide. Many countries sent medical aid.
Vargas Disaster (02:56)
In December 1999, heavy rains inundated Venezuela's Cordillera de la Costa and saturated the ground. Landslides buried Los Corales, Caraballeda and other coastal towns in mud and rock.
Vargas Rescue Efforts (04:06)
Up to 30,000 people died in Venezuela's 1999 landslide that reshaped 38 miles of coastline. The military evacuated 70,000 survivors to Caracas. Hugo Chavez refused U.S. naval aid, fearing an invasion, and appealed to citizens to “adopt a family.”
El Salvador Earthquake (03:35)
In January 2001, an earthquake 60 miles off the coast triggered landslides across the country and in Guatemala. Las Colinas and San Miguel suffered losses and San Salvador residents fled homes during aftershocks. 850 people died and more than 4,000 were injured.
Deforestation and Destruction (01:47)
In February 2001, two major earthquakes struck El Salvador after the initial January quake, killing and injuring hundreds more. Citizens blamed property developers for stripping the hills of trees and causing landslides.
Predicting Landslides (01:59)
Scientists study weather patterns and monitor risk areas for sudden stream flow changes to warn residents and officials. Trench excavation, ledges, and wire mesh can reduce landslide effects, but deforestation will continue to increase risk.
Credits: Devastating Landslides: The World's Worst Disasters (00:50)
Credits: Devastating Landslides: The World's Worst Disasters
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