Alaska’s Shishaldin volcano spews a 5.5-mile-high ash cloud

On Tuesday, July 18, an ongoing volcanic eruption in the Aleutian Islands of Alaska produced a large ash cloud that prompted warnings from the National Weather Service to pilots of potentially hazardous conditions. Volcanic ash can cause a jet engine to stall due to the sharp, angular texture of the spray.

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The Alaska Volcano Observatory said the ash plume initially had a height of about 5.5 miles and was reported after an eruption from the Shishaldin volcano. Ash emissions dropped below 1.9 miles in the afternoon and the advisory for pilots was lowered. As of Wednesday morning Eastern Time, the volcano is at an orange alert level.

Mount Shishaldin began to erupt on July 11, and a US Coast Guard flight confirmed an increase in lava eruptions within the summit crater, according to a report from the Associated Press. On Friday, July 14, a significant explosion produced an ash cloud that reached a height of up to 7.5 miles and moved south into the Pacific Ocean, preceding a second, smaller explosion.

The volcano is about 700 miles southwest of the city of Anchorage and toward the center of Unimak Island. The island is home to approximately 65 residents who live in the False Pass community, about 25 miles northeast of the volcano.

Mount Shishaldin is one of the most active volcanoes in the Aleutian Arc, a 1,553-mile-long line of 80 volcanic mountains with 41 having been active since at least 1760. The arc stretches along the southern tip of the sea from Bering to the Alaska Peninsula and is the boundary between the Pacific and North American tectonic plates.

The symmetrical cone volcano has a base diameter of 10 miles and a 660-foot funnel-shaped crater that often emits steam and occasionally a little ash. Mount Shishaldin has erupted at least 26 times since 1824. Most of these eruptions have been small, with one in 1999 producing an ash cloud that reached 8.5 miles.

[Related: How scientists helped Alaska’s “Rat Island” shake off its namesake rodents.]

According to the US Army Corps of Engineers, volcanoes have had both constructive and destructive influences on the Aleutian Arc. Eruptions have helped create islands through fresh lava and ash flows, but they have also destroyed islands. Bogoslof Island, on the eastern side of the Aleutians, has undergone rapid construction and destruction that has influenced its shape over time.

The Centers for Disease Control and Prevention (CDC) encourages those who live in front of any active volcano to evacuate if told to do so, shelter in place by sealing all doors and windows, and keep a disaster supply kit.

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