Which volcano produced the 1980 eruption that began with a massive north-flank landslide?

Mount St. Helens produced the 1980 eruption that began with a massive north-flank landslide.

The Washington State volcano erupted catastrophically on 18 May 1980 after weeks of earthquakes, steam explosions, and visible bulging on its northern flank. A magnitude 5.1 earthquake triggered the largest recorded landslide in history, removing the summit and releasing pressure from the volcano’s magma system.

The landslide was followed by a powerful lateral blast that devastated forests across an area of roughly 600 square kilometres. Ash rose high into the atmosphere, and lahars—fast volcanic mudflows—ran down river valleys. Fifty-seven people and thousands of animals died, while roads, bridges, and buildings were destroyed.

Mount St. Helens is a stratovolcano in the Cascade Range, a chain created by subduction of the Juan de Fuca Plate beneath the North American Plate. The eruption changed modern volcano monitoring and remains a major case study in landslide-triggered volcanic hazards.