The Alaska Volcano Observatory (AVO) reported that an increased seismic activity at the volcano was first noted in April 2024, following the repair of seismic monitoring stations after a months-long outage.
Since then, over 900 earthquakes have been recorded this year, clustered in two regions: one at depths of 0 to 6 miles (0 to 10 km) beneath the volcano, and another at 12 to 22 miles (20 to 35 km) southeast of the Crater Peak vent. The largest earthquake, with a magnitude of M 2.3, occurred on October 6, 2024. The weekly rate (~20 earthquakes) and magnitude have remained steady since April. This increase in seismic activity bears similarities to previous episodes at the volcano, such as those between August 1991 and June 1992, which preceded the 1992 eruptions, and between 2004 and 2006, when heightened seismic activity accompanied significant summit heating and ice cap melting.
A ground deformation, detected via Global Navigation Satellite System (GNSS) stations on the volcano’s flanks, began in March 2024 and has steadily continued, indicating ongoing volcanic inflation. The stations closest to the deformation source have recorded about 1.6 inches (4 cm) of horizontal movement since the onset of the episode. Preliminary models suggest pressurization, likely due to magma or fluid inflow, or gas exsolution, at depths of 2 to 3 miles (3 to 5 km) and approximately 2 miles (3 to 4 km) west of Mount Spurr. Satellite radar data from September 2023 to September 2024 corroborate the GNSS measurements of this ongoing deformation.
The AVO added: „Seismic unrest and ground deformation has been accompanied by the formation of a small lake in the summit crater of Mount Spurr in early summer 2024. The lake first appeared between May 15 and June 15 and was well documented during a June 23 overflight when it had an area of about 1 acre (~3800 square meters or roughly the size of a football field). The crater lake grew marginally over the summer to a diameter of around 280 feet (85 meters) and an area of approximately 1.4 acres through small collapses and melt of glacial ice inside the crater (https://avo.alaska.edu/image/view/196117). The lake is partially covered by ice and remains blue-green in color. Active steaming from summit area steam vents called fumaroles is visible along and above the northeastern lake shore and crater wall, and from a pit in the ice on the northeast crater rim. The vigor of steaming has not visibly changed over this current period of unrest and remains similar to observations from recent years. No volcanic mudflows (also called lahars) or other signs of significant ice and snow melt have been observed in the summit region or in Crater Peak. The last time a crater lake formed at the summit of Mount Spurr was during seismic unrest and a likely intrusion of magma in 2004 that did not lead to an eruption.
The June 23 overflight also monitored gas emissions from the volcano and detected low levels of sulfur dioxide and carbon dioxide. The measured compositions are similar to background levels measured in previous years. Deep intrusion of magma is sometimes associated with anomalously high volcanic carbon dioxide emissions, but no such anomaly was detected during the overflight.“
Source: Alaska Volcano Observatory volcano activity update 10 October 2024