Mount Shishaldin is a moderately active volcano on Unimak Island in the Aleutian Islands chain of Alaska. It is the highest mountain peak of the Aleutian Islands. The most symmetrical cone-shaped glacier-clad large mountain on Earth, the volcano's topographic contour lines are nearly perfect circles above. The lower north and south slopes are somewhat steeper than the lower eastern and western slopes. The volcano is the westernmost of three large stratovolcanoes along an east–west line in the eastern half of Unimak Island. The upper is almost entirely covered by glacial snow and ice. In all, Shishaldin's glacial shield covers about. It is flanked to the northwest by 24 monogenetic parasitic cones, an area blanketed by massive lava flows. The Shishaldin cone is less than 10,000 years old and is constructed on a glacially eroded remnant of an ancestral somma and shield. Remnants of the older ancestral volcano are exposed on the west and northeast sides at elevation. The Shishaldin edifice contains about of material. A very steady steam plume rises from its small summit crater which is about across and slightly breached along the north rim. In 1967, Shishaldin Volcano was designated as a National Natural Landmark by the National Park Service.
Name
The Aleuts named the volcano Sisquk or Sisagux, meaning "mountain which points the way when I am lost." The spelling Shishaldin comes from the Russian version, Шишалдина, of the Aleut name.
Activity
This volcano has had many recorded eruptions during the 19th and 20th centuries, and a couple reports of volcanic activity in the area during the 18th century may have referred to Shishaldin as well. Therefore, the volcano's entire recorded history is spotted with reports of activity. AVO has 24 confirmed eruptions at Shishaldin, making it the volcano with the third most confirmed eruptions. However, Shishaldin has the most eruptions in Alaska, but half of the eruptions are unconfirmed. Recent, well-documented eruptions were in 1995–96 and 1999. Since the 1999 eruption, it has maintained seismic activity, typically having very low-magnitude volcanic earthquakes every 1–2 minutes. During this period of non-eruptive seismic activity, it has been puffing steam, with puffs also occurring about every 1–2 minutes. There were reports in 2004 of small quantities of ash being emitted with the steam. A new period of activity started July 2019 with incandescence observed in the summit crater during a time of increased seismic activity. On July 23, an active lava lake and minor spattering within the summit crater was observed. A new lava effusion event began on October 13 advancing over the next several weeks. The summit cone partially collapsed on November 25, producing a pyroclastic flow down the northwest side of the volcano and a new lava flow. On December 12, a short-lived explosion from Shishaldin expelled an ash cloud to 20-25,000 ft. During late December, eruptive activity continued with lava flows and low-level explosive activity at the summit. On January 3, 2020, seismicity led to an ash cloud eruption which reached as high as 27,000 feet. Another large ash cloud was emitted January 19 2020. The Alaska Volcano Observatory monitors the volcano for more hazardous activity with seismometers and satellite images. Visual observations are rare, because of the remote location of the volcano.
Climbing
The first recorded ascent of Shishaldin was in 1932, by G. Peterson and two companions. Given the straightforward nature of the climbing, it is possible that an earlier ascent occurred, either by native Aleuts, Russians, or other visitors. Shishaldin is a popular ski descent for local climbers. Due to its remoteness, Shishaldin is not often climbed by outsiders.
