An explosion at one of Alaska's most active volcanoes has led scientists to raise its alert level to "watch." This comes after the Alaska Volcano Observatory (AVO) lowered Cleveland Volcano's alert level in early May after nearly a year and a half of inactivity.
Cleveland is located on an uninhabited island in the central Aleutians, west of Umnak Island. Around 10:30 p.m. on Monday, the AVO detected a small explosion that sent an ash plume 22,000 feet, traveling to the south.
Hannah Dietterich, a research geophysicist with the observatory, said Cleveland Volcano usually stays at an elevated color code, but on May 7, scientists lowered the aviation color code and alert level to "unassigned" since it had gone so long without signs of activity.
"Cleveland Volcano has been erupting semi-continuously for more than a decade," said Dietterich. "These very short duration, small eruptions happen pretty frequently over time. But our last one was actually back in January of 2019. Since then, it's become very quiet. It hasn't even been very warm recently. So the system kind of closed up."
Dietterich said the lack of recent activity is out of character for Cleveland, which has been erupting steadily for the past 20 years.
The near year and a half that passed since the volcano's last eruption in January of 2019 is the longest time Cleveland has gone without an eruption since 2005, said Dietterich.
She said Cleveland has a history of cycles of explosions and that the AVO will continue to monitor the volcano closely.