Mount Shishaldin, a spectacular 9,373-foot symmetrical cone on Unimak Island, has been erupting since July 11, but the explosion on July 18 was the largest so far. The Alaska Volcano Observatory reported that the ash cloud reached approximately 32,000 feet (over six miles) above sea level, prompting a red aviation alert — the highest warning level — for aircraft traversing one of the busiest air cargo corridors on the planet. Pilots were warned that ash particles, which are sharp and abrasive, can cause jet engines to fail if ingested.
Shishaldin is the highest peak in the Aleutian Islands chain and one of the most frequently erupting volcanoes in Alaska, with 24 confirmed eruptions since 1775. Unlike the explosive 1999 event, which sent ash 8.5 miles high, the current eruption has been a week-long sequence of smaller explosions interspersed with lava activity within the summit crater. A U.S. Coast Guard overflight confirmed fresh lava flows early in the eruption cycle, and satellite imagery has tracked the ash plume drifting south over the Pacific Ocean, away from major population centers. The nearest settlement, False Pass, with a population of under 100, received a light dusting of ash but was not in immediate danger.
The Aleutian Islands sit on the Pacific Ring of Fire, where the Pacific Plate subducts beneath the North American Plate. This geological setting produces some of the most active volcanoes on Earth, including Shishaldin, which is built on a base of older volcanic deposits and has been active for roughly 10,000 years. The volcano's nearly perfect conical shape makes it one of the most symmetrical stratovolcanoes in the world, comparable to Japan's Mount Fuji. Volcanologists continue to monitor seismic activity and gas emissions closely, as the eruption could either subside or escalate into a larger event in the coming days.
Knowledge takeaway: Shishaldin is one of Alaska's most active volcanoes with 24 confirmed eruptions since 1775; the July 18, 2026 ash cloud reached over six miles high, triggering aviation red alerts across the North Pacific; and the volcano sits on the Pacific Ring of Fire where the Pacific Plate subducts beneath the North American Plate, producing frequent volcanic activity for the past 10,000 years.