The Weekly Volcanic Activity Report: August 13–19, 2025
New activity/unrest was reported for 7 volcanoes from August 13 to 19, 2025. During the same period, ongoing activity was reported for 20 volcanoes.
Mount Spurr quiets after prolonged unrest, alert and aviation codes downgraded
The Alaska Volcano Observatory lowered the Volcano Alert Level for Mount Spurr to Normal and the Aviation Color Code to Green at 10:07 AKDT (18:07 UTC) on August 20, 2025, following a gradual decline in unrest and the absence of ground deformation since March 2025.
Caldera cliff collapses in Santorini’s Imerovigli, triggering slope instability concerns
A large landslide occurred in the village of Imerovigli on the island of Santorini, Greece, at 15:30 LT (12:30 UTC) on August 20, 2025, collapsing part of the volcanic caldera cliff and generating a dense dust cloud over the area.
Mount Ruapehu Crater Lake heating up, New Zealand
Mount Ruapehu Crater Lake is warming again, with temperatures rising to 16°C (61°F) by August 19, 2025. The Volcanic Alert Level remains at 1, indicating minor volcanic unrest.
Lava reaches lower southern slope of Etna, 2 km (1.2 miles) from Altamontana trail
New lava flow from Mount Etna’s summit is advancing along the southern flank, reaching an elevation of about 2 270 m (7 450 feet). The most advanced front is now located about 2 km (1.24 miles) from the Altamontana trail, a major access route used for monitoring and hiking, following effusion that began on August 9, 2025.
Lewotobi volcano eruption sends ash cloud to 9.8 km (32 000 feet), Indonesia
Lewotobi volcano in Indonesia erupted on August 17, 2025, emitting volcanic ash up to 9 800 m (32 000 feet) above sea level, according to the Darwin Volcanic Ash Advisory Center (VAAC).
New lava vent opens between Etna’s Bocca Nuova and Southeast Crater, Italy
A new lava vent has opened between Bocca Nuova and Southeast Crater on Mount Etna, Italy, at an elevation of about 2 980 m (9 777 feet), producing a steady lava flow and explosive activity at Southeast Crater.
Mount Marapi eruption generates thick ash column drifting northeast, West Sumatra, Indonesia
Mount Marapi in West Sumatra, Indonesia, erupted at 08:39 local time (LT) on August 12, 2025, producing an ash plume approximately 1 600 m (5 250 feet) above the summit, or about 4 491 m (14 735 feet) above sea level, drifting toward the northeast.
Volcanic alert level raised for Bur ni Telong, Indonesia
Indonesia’s Bur ni Telong volcano was placed on alert level II (Waspada) at 06:00 local time (LT) on August 2, 2025, following a rise in deep and shallow volcanic earthquakes between July 30–August 5, 2025. The last eruption at this volcano took place in 1937.
Seismic swarm with more than 700 low-magnitude earthquakes detected beneath Teide, Tenerife
More than 750 volcano-tectonic and hybrid earthquakes were recorded beneath the Teide–Pico Viejo volcanic complex in Tenerife, Canary Islands between August 6 and 7, 2025. This includes two seismic swarms at depths of 8–14 km (5–9 miles), with the largest event reaching M1.5.
