23 May 2006

The Alaskan volcano, Mount Cleveland erupts.

Eruptions from Mount Cleveland are generally vulcanian and strombolian in nature, characterized by short explosive ash clouds sometimes accompanied by a’a flows, lava fountains, pyroclastic flows, ash and steam emissions, lava dome growth, and the ejection of breadcrust bombs. Hot springs were reportedly found on the volcano in the 1800s, and persistent fumarolic activity was observed in the 1980s and 1990s. Mount Cleveland is a site of persistent steam emissions and thermal anomalies that represent constant background activity. During 2011, a summit lava dome formed, by continuous intrusion of magma at the summit. Late in 2011, nearly 6 explosions demolished the dome. In June 2012, another small dome was observed.

Little is known about Cleveland’s early eruptive history as its remoteness makes it a difficult area to investigate, and discrepancies in names have caused confusion between events there and those on nearby Carlisle. Even today, not all possible events are confirmed as eruptions by the Alaska Volcano Observatory, and many are listed as “possible.” In observed history, Mount Cleveland may have first erupted in 1744; the first confirmed eruption occurred in 1828. The volcano erupted again in 1836, 1893, 1897, 1929, 1932, and 1938.

The first notable eruption from Mount Cleveland was a Volcanic Explosivity Index 3 Vulcanian eruption that occurred between June 10 and June 13, 1944. Lava flows extended 5 km from the summit, and an ash plume 6,000 m high was produced. Large boulders were reportedly ejected and carried out to sea by eruptive force. The eruption had the distinction of being the only confirmed direct volcanic fatality in Alaska; a small detachment from the Eleventh Air Force was stationed on the volcano at the time, and one Sergeant Purchase left his post early in the eruption to take a walk and never returned, probably killed by mudslides. At approximately 10:20, a boat sent to search for Purchase witnessed the end of the eruption. The island was abandoned for the remainder of the war.

Mount Cleveland erupted more recently in 1951, 1953, 1954, 1975, 1984 through 1987, 1989, 1994, and 1997. The volcano has received more focused attention in recent times due to its increased activity: it erupted in 2001, 2005, three times in 2006, 2007, three times in 2009, and twice in 2010. Of these, the most significant eruption was the 2001 eruption, which produced a 12 km high ash plume. This plume dispersed 120 to 150 km 75 to 93 mi across Alaska, an unusual distance that allowed detailed satellite observations to be made. Nikolski and the surrounding region was the site of several hours of ashfall, represented in satellite imagery as areas of discolored snow.This eruption significantly disrupted air traffic in the area.

On June 19, 2012, a pilot reported an ash-producing explosion on Mount Cleveland. Due to continuing seismic activity, the volcano was placed on the USGS Volcano Watch List in the orange or “watch” category the following day. AVO continues to keep Cleveland on the watch because of a persistent anomaly at the summit. AVO suspects it could be dome growth. Other minor ash producing explosions occurred on June 26, July 12, and August 19.