Copyright Information: All images are in the public domain and available for free. If you use this image, credit NOAA/NGDC, University of Colorado at Boulder. |
The growing lava dome in the explosion crater as it appeared on May 19, 1983, three years after the main eruption. The dome is built from a composite of lava lobes extruded onto the surface during different eruption phases. Material is also added to the dome from within. As the composite dome increases in size, chances increase for collapses of its sides which could trigger pyroclastic flows and rock falls from the crater walls. Image Credit: University of Colorado at Boulder May 18, 1980 Mount Saint Helens USA volcano An earthquake occurred at 15 32 UT, only seconds before the explosion that began the eruption of Mount St. Helens volcano. This eruption and blast blew off the top of the volcano, reducing its elevation by 396 meters, killed 31 people and caused an estimated property damage of between $0.5 billion and $2 billion. About 53 earthquakes having magnitude larger than 4.5 were located near Mount St. Helens before the main event and eruption. No earthquakes having magnitudes higher than 4.5 were located following the eruption. |
|
