2021 Volcanic activity in Alaska and the Commonwealth of the Northern Mariana Islands—Summary of events and response of the Alaska Volcano Observatory

Abstract

In 2021, the Alaska Volcano Observatory responded to eruptions, volcanic unrest or suspected unrest, increased seismicity, and other significant activity at 15 volcanic centers in Alaska and the Commonwealth of the Northern Mariana Islands. Eruptive activity in Alaska consisted of repeated small, ash-producing, phreatomagmatic explosions from Mount Young on Semisopochnoi Island; an explosion at Great Sitkin Volcano followed by the eruption of a thick lava flow that filled and overflowed the summit crater; weak explosive activity and the eruption of small, channelized flows at Pavlof Volcano; and a short-lived eruption at Mount Veniaminof that produced ash emissions from an intracaldera cone, as well as lava flows confined to a melt pit in the ice mantling the cone's flank. Mount Cleveland had a period of unrest, but no eruptive activity took place there. Anomalous seismicity was also detected at Atka volcanic complex, Mount Gareloi, and Davidof volcano. New warm springs opened and deposited mud at the summit and north base of Shrub mud volcano. Other activity of note in Alaska consisted of large ice and rock avalanches at Iliamna Volcano and Mount Spurr, ash resuspension events at Mount Katmai and Aniakchak Crater, and anomalous deformation at Mount Okmok that was consistent with a shallow intrusion of magma. In the Commonwealth of the Northern Marianas Islands, a brief, ashproducing eruption occurred at Mount Pagan. Aviation Color Code/ Volcano Alert Level Date and time of change (UTC) Shrub mud volcano UNASSIGNED No change for entire year Mount Katmai (Novarupta) GREEN/NORMAL No change for entire year Mount Veniaminof GREEN/NORMAL Beginning of year UNASSIGNED 01/15/2021 (21:33) ORANGE/WATCH 03/04/2021

Detection and Characterization of Seismic and Acoustic Signals at Pavlof Volcano, Alaska, Using Deep Learning

“…Background activity at Pavlof Volcano from January to May 2021 was characterized by AVO as occasional short, low-energy bursts of seismic tremor and long-period earthquakes (Orr et al, 2024). On 11 May 2021, gliding harmonic tremor was first noted during duty checks alongside several moderately deep long-period earthquakes located 15-20 km below sea level.…”