Warming up of Mt. Wrangell

Of more than a normal interest is the heating up of the summit region of Alaska's Mt. Wrangell the past 20 years. The increase in upward heat flow in a small crater on the rim of the volcano's summit caldera at altitude 4000 m (14,000 ft) does not necessarily mean that an eruption is imminent. But an eruption is an obvious possibility. Mt. Wrangell has been far from inactive in historic times. During the major Yakutat earthquakes in September, 1899, Wrangell increased its output of smoke and ash. The summit caldera, which has a diameter of 6 km, may have been formed as recently as 2,000 years ago.

In addition to the usual hazards associated with volcanic eruptions, ice-clad volcanoes like Mt. Wrangell present other hazards to the surrounding areas. Catastrophic flooding by waters from rapid melting of ice and snow on a volcano's flanks have occurred in Alaska as well as in Iceland and the volcanic Cascades of Washington and Oregon.

Mudflows pose another serious problem that can directly devastate property or contribute to outburst flooding by temporarily damming of rivers.

The most recent warming up of Mt. Wrangell began shortly after the 1964 Good Friday Earthquake. Dr. Carl Benson, who has studied the volcano for more than two decades, suspects that the earthquake may have started the warm-up by jiggling something loose in the volcanic plumbing within the mountain.

The warming up of Mt. Wrangell is clearly shown by the melting of glacier ice in the volcano's North Crater. Almost unnoticeable twenty years ago, the North Crater on the caldera rim is now a nearly ice-free pit 200 meters (600 ft) deep. Active steam vents on the crater floor discharge heat energy at a rate of about 100 megawatts. That is enough energy to provide electrical power for a city of perhaps 10,000 people.