A volcano in Alaska's remote Aleutian Islands has started discharging lava, a signal that the mountain may explode and launch an ash cloud that could threaten aircraft. The Alaska Volcano Observatory said satellite images showed lava is building in the crater at the summit of the 1,730-meter Cleveland Mountain on the uninhabited Chuginadak Island, about 1,500 kilometers southwest of Anchorage. "It's forming a dome-shaped accumulation in the crater," said Chris Waythomas of the U.S. Geological Survey, the observatory's top scientist. "We call these things 'lava domes'." Lava domes form a lid on a volcano's upward lava flows, including the chamber holding the magma. When they grow big enough, lava domes become unstable and sometimes collapse, decompressing the magma chamber and leading to an explosion, Waythomas explained. "They can seal up the conduit and prevent gasses from escaping and lead to an explosive event," he said. Such an explosion from the volcano on Chuginadak could send an ash cloud more than 6,000 meters into the air, the observatory said. The biggest threat from ash clouds is to aircraft. The Federal Aviation Administration (FAA) and the airline industry become concerned for trans-Pacific flights when an ash cloud has the potential to exceed the 6,000-meter threshold, as Cleveland Mountain has done in the past. The nearest village, Nikolski, is on another island about 80 kilometers east, and previous eruptions of Cleveland were not considered a danger to its 18 permanent residents. "The plume would have to head directly to Nikolski to cause any problems," Waythomas said.
