how could the combination of high rain fall, steep slopes and earthquakes be lethal for a populated area near a volcano?
Answers
Answer:
Volcano Hazards Program
Landslides are common on tall, steep, and weak volcanic cones
After the May 18, 1980 eruption, Mount St. Helens' elevation was only 8,364 feet (2,550 meters) and the volcano had a one-mile-wide (1.5 kilometers) and approximately 600 m (2000 ft) deep horseshoe-shaped crater. View here is from the northwest.
(Credit: Casadevall, Tom. Public domain.)
Landslides are large masses of wet or dry rock and soil that fall, slide, or flow very rapidly under the force of gravity. Landslides commonly originate as massive rock falls or avalanches, which disintegrate during movement into fragments ranging from small particles to blocks hundreds of meters across. If the landside is large enough and contains a high-enough percentage of water and fine material (typically, >3-5 percent of clay-sized particles), it may transform into a lahar that can travel as much as 200 km (120 mi) downstream.