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Geography

Why Volcanic Edifices Collapse Laterally and Generate Debris Avalanches

Quick fact

Some volcanic debris avalanches have traveled more than 100 kilometers from their source, as seen in the 1980 Mount St. Helens eruption, which removed the entire north flank in seconds.

Why this is interesting

Every volcano looks like a solid, permanent mountain—but some have suddenly lost a massive chunk of their flank, unleashing a catastrophic avalanche. What makes a volcano fail so dramatically?