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A small burst of incandescent lava fragments shoots skyward during strombolian-type explosive activity from Mount Veniaminoff volcano in Alaska. The explosion occurred from a cinder cone within the volcano's ice-filled caldera (caldera rim is visible to right of cone). When observed by scientists on July 13, 1983, lava fragments were ejected every 1 to 2 minutes as high as 300 m and a sluggish lava flow about 20 m wide had moved down the cone (right side). Between June 1983 and January 1984, a series of small explosions, lava fountains, and lava flows erupted from the cone. More information about Veniaminoff. Similar explosive activity built the Red Cones, two small cinder cones located about 5 km SSW of Mammoth Mountain. Hazard zones for this type of eruption are much smaller than hazard zones for the type of explosive activity that occurred along the Mono-Inyo Craters volcanic chain in the past 5,000 years. Since the Mono-Inyo chain has been the source for all of the recent eruptions in the Long Valley area, scientists have developed hazard zones that are based on explosive eruptions from vents located along this chain. Most eruptions of the Mono-Inyo Craters volcanic chain generated pyroclastic flows and surges, columns of ash, and viscous lava flows (domes). Although scientists cannot predict the actual size and type of the next eruption in the Long Valley area, once an eruption gets underway, they will be able to update or modify the volcano-hazard zones to more closely relate to the actual activity. For example, if basalt magma is erupted instead of rhyolite, less extensive hazard zones would be appropriate than the more extensive zones associated with explosive rhyolite magma, which typically has erupted from the Mono-Inyo chain. |
