Sierra Negra volcano (Galapagos): strong earthquakes precede the start of a first fissure eruption since 2005

After two prolonged seismic crises with earthquakes up to M5.3, the Sierra Negra volcano entered a new eruptive phase with strong fountaining and multiple lava flows on Tuesday 26 June 2018 - the first volcanic activity since its last eruption in 2005.

A recent seismic crisis represents the culmination of about 2 years of steady increase in seismic activity beneath the volcano (read our 14 June 2018 news update here). The Geophysical Institute of Ecuador (IGEPN) reported a M5.3 earthquake occurred beneath the volcano at a depth of about 5.3 km at 03h15 Galapagos Time (TG). This earthquake was preceded by a M3 event at 3h10 and followed by a series of aftershocks of magnitude 3 -4, all of which were felt in the village of Puerto Villamil, 20 km SE of the volcano.

After a short pause, a new swarm of earthquakes started at 11h17 TG, at depths between 3 and 5 km and magnitudes up to 4.6. This seismic unrest continued until around 13h38 TG a change in the seismicity was observed with increasing amplitudes between the seismic and infrasound signal, indicating the onset of a new eruption. This new eruptive phase was quickly confirmed by a GOES-16 satellite image showing a strong anomaly of heat in the northern area of the volcano's caldera, suggesting the presence of lava flows in this area.

Subsequent eye witness reports from the Galapagos National Park employees indicate that some lava flows are running into the caldera but that there is also lava flowing towards the north flank in the direction of Bahía Elízabeth. A tall ash column moving in westerly direction was also observed. First images of this eruptive phase were soon shared on social media, showing lava fountains from newly opened fissures which create multiple rivers of lava flowing towards the ocean.

Sierra Negra is a large basaltic shield volcano with a 9 km by 7 km caldera located on Isabela, the largest island of the Galapagos. At least 250 people have already been evacuated from communities in the immediate vicinity of the volcano. All tourist and school activities near the volcano have been suspended according to Secretary of Risk Management, Alexandra Ocles, who said the eruption is currently moderate.

This eruption starts only 10 days after the youngest and most active Galapagos volcano, Cerro la Cumbra on the neigbouring, uninhabited, island of Fernandina, started a new fissure eruption with fountaining and lava flows that quickly reached the ocean (you can read our article on this eruption here)

Some first image of the new fissure eruption during the afternoon of 26 June were shared on the Facebook page Galápagos Naciente:

You can find an impressive set of night-time images of the new eruption on the Facebook page of Christian Saá: