Spurr

Seismometers such as this one installed near Mount Spurr volcano (on skyline in background) provide the Alaska Volcano Observatory with a continuous, radio-telemetered record of volcanic earthquakes. These data are used to monitor the state of activity at the volcano and are essential for issuing timely warnings of eruptions. Ash from its 1992 eruption darkens the slopes of Crater Peak, in the center below the sharp-peaked summit of Mount Spurr, in this 1993 photo from the south.