| Mount St Helens | Long Valley | |
| On May 18, 1980, after a long period of rest, this quiet mountain in Washington provided detailed observations on the mechanics of highly explosive eruptions. | This field seismometer measures earthquakes associated with subsurface volcanic forces and may help to predict future events. It sits on a plateau known as the "Volcanic Tableland" formed by a major eruption 600,000 years ago. |
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