How much ash was there from the May 18, 1980 eruption of Mount St. Helens?

• Yellowstone is one of a few dozen volcanoes on earth capable of "supereruptions" that expel more than 1,000 cubic km of ash and debris.
• The plumes from such eruptions can rise 30 to 50 km into the atmosphere, three to five times as high as most jets fly.
• Yellowstone has produced three supereruptions in the past 2.1 million years. The most recent was

Left: Before the eruption of May 18, 1980, Mount St. Helens' elevation was 2,950 m (9,677 ft). View from the west, Mount Adams in distance. S. Fork Toutle River is valley in center of photo.

Right: Mount St. Helens soon after the May 18, 1980 eruption, as viewed from Johnston's Ridge.

The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.

Video Sections:

• Volcanoes: Monitoring Volcanoes

Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon. Spectacular debris flow footage, recorded by Franck Lavigne of the

USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.

Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.

USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.

The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.

Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier. On October 1, 2004, the first of several explosions shot a plume of volcanic ash and gases from a vent on the

Compilation video of significant events from the dome-building eruption at Mount St. Helens, from October 1, 2004 to March 15, 2005, including steam and ash eruptions, growth of lava spines, helicopter deployment of monitoring equipment, collection of lava samples, and FLIR thermal imaging of rock collapse on lava dome.

1. Eruption of Mount St. Helens,  October 1