An ash cloud has been in the news for the past month since the eruption of a volcano in Iceland. But today, people are talking about another ash cloud - one that happened thirty years ago.
On May 18, 1980, the Mount St Helens volcano erupted in the northwestern US state of Washington. It blew an ash cloud around the world.
The volcano's north flank collapsed within minutes of a 5.1 magnitude earthquake that morning. That triggered the largest landslide ever recorded.
The eruption destroyed forest and rained volcanic ash for kilometres.
The numbers are staggering:
Scientists have been drawn to Mount St Helens to study volcanoes, ecosystems and forestry. The area is continuously monitored for earthquakes.
'It's a terrific opportunity for people to understand the forces of the Earth,' says one scientist.
The volcano continued to erupt lava until 1986. The photos on this page show Mount St Helens in 2004.
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