Mount Shishaldin

Shishaldin Volcano, or Mount Shishaldin, is a moderately active volcano on Unimak Island in the Aleutian Islands chain of Alaska in the United States. It is the highest mountain peak of the Aleutian Islands and rises about 10,000 m from the bottom of the Aleutian Trench 140 mi south of the volcano. The volcano's topographic contour lines are nearly perfect circles above 6500 ft. The lower north and south slopes are somewhat steeper than the lower eastern and western slopes. Only on the volcano's west flank between about 3500 to 6500 ft are small areas of rough topography which are remnants of an older collapsed volcano upon which Shishaldin is built. The volcano is the westernmost of three large stratovolcanoes along an east–west line in the eastern half of Unimak Island.

The upper 6600 ft is almost entirely covered by glacial snow and ice. In all, Shishaldin's glacial shield covers about 35 sqmi. 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 4900 to 5900 ft elevation. The Shishaldin edifice contains about 300 km3 of material. A very steady steam plume rises from its small summit crater which is about 500 ft across and slightly breached along the north rim. In appearance, the volcano can vary from nearly completely white to almost all black, depending on the occurrence of ashfall deposits.

In 1967, Shishaldin Volcano was designated as a National Natural Landmark - the Shishaldin Volcano National Natural Landmark - by the National Park Service. The landmark is 62714 acre and a plaque was erected near the coast.

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 of 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 (after Akutan and Pavlof). However, Shishaldin has the most eruptions (this means confirmed and possible 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 (most are below magnitude 1) 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. In 2014, a low-level effusive eruption cycle started which lasted into 2016.

A new period of activity started in 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 20000 - 25000 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 that reached as high as 27000 ft. Another large ash cloud was emitted on January 19, 2020. This event ended shortly afterwards with an abrupt end in seismicity. The lava flows emitted during the eruptive events have cut deep channels in the snow and ice mantle of the volcano's north slope.

After more than two years of dormancy, another eruptive cycle began and on 14 July 2023, the volcano emitted ash plumes up to 40000 ft high after several explosions at the summit. Fourteen significant explosive events occurred at Shishaldin between 12 July and 3 November 2023. After the November 3 explosive event, much smaller explosions, steam and gas emissions and collapse events around the summit crater rim occurred frequently for about a week, By January 2024, only minor steam emissions and small events deep in the summit crater continued.

The Alaska Volcano Observatory monitors the volcano for more hazardous activity with seismometers and satellite images. Due to the remote location of the volcano, visual observations are rare.

Climbing
The first recorded ascent of Shishaldin was in 1932, by G. Peterson and two companions. Given the straightforward nature of the climbing (Alaska Grade 1, snow up to 40 degree slope), it is possible that an earlier ascent occurred, either by native Aleuts, Russians, or other visitors. Shishaldin is rather unique in that its appearance changes very little to a climber during an ascent. A group climbing Shishaldin in May, 2005 set a base camp at 2,500 ft on the east side after a four day hike and ski trip from the village of False Pass. As they climbed the cone, they noted "we could never believe it was so tall since the summit always looked 'so close'. Yet it never seemed to get any closer!" It took that group about 8 hours to climb to the top. Shishaldin is a popular ski descent (6,000 ft vertical) for local climbers (of whom there are few). Due to its remoteness, Shishaldin is not often climbed by outsiders.