Sierra Negre volcano news & eruption updates (Galapagos Islands, Ecuador)
Sierra Negra volcano (Galapagos): strong earthquakes precede the start of a first fissure eruption since 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:
Links / Sources:
Lava stopped flowing at Sierra Negre volcano on the evening of 30th of Oct. 2005.
However, even 10 days after the end of the eruption, fires caused by the eruption continued, threatening some rare plants on the island. About 500 hectars in the National Park were burning on the W flank of the volcano in an area called Pampas de Velasco. This area is home to the largest population in the islands of the rare endemic plant Scalesia cordata, which was threatened by the fires. Therefore, the local authorities decided to intervene and take costly measures to extinguish the bushfire.
The eruption of Sierra Negre continues with lava flows confined to the vast caldera; it does not pose risks to populated areas. In the meanwhile, a group of scientists from the Geophysical Institute of Ecuador have visited the site and posted a detailed report about the eruption's first 3 days: it can be downloaded here.[more]
The eruption is continuing from a fissure inside the E part of the caldera of Sierra Negre, with lava fountains up to 200 m tall and large lava flows that have now covered about 20% of the caldera floor. Good eruption viewing possibilities are from a lookout on the caldera rim in the El Cura area.[more]
First photographs and more detailed information about the large eruption of Sierra Negre are emerging. As on Monday, 24 October, lava flows from a fissure have travelled 9-10 km away from the fissure. The eruption is accompanied by strong lava fountains. Near the eruption site, the terrain consists mainly of older, unvegetated lava flows. Two flows are travelling towards Elizabeth Bay, while a third one is heading towards Cartago Bay, both uninhabited areas.
The popoluation of Puerto Villamil is not threatened because of its sheltered position at the S of the island.
Eruption of Sierra Negre volcano (23 Oct. 2005):
What is nearby? Near the eruption site, the terrain consists mainly of older, unvegetated lava flows. The popoluation of Puerto Villamil is not threatened becaused of its sheltered location at the S of the island. Because of the geologic characteristics (being a typical hot spot volcano, such as Hawaii), the volcanos of the Galapagos Islands produce very fluid lava flows (low viscosity) that permits the flows to travel over great distances.
Evolution of the eruption:
1) The eruption began, at 17:30 h local time on Sunday, 23 Oct. 2005, with a powerful explosion that emptied the uppermost batch of gas-charged magma, heard until 25 km away from the volcano. In addition to the noise of the explosion, a strong smell of sulphur was notised.
2) A gas and ash column rose to about 20 km above the volcano.
3) From a fissure (inferred from photographs), lava fountains started to produce lava flows observed by park rangers. Two flows are travelling towards Elizabeth Bay, while a third one is heading towards Cartago Bay. The lava flows (as on Mon. 24th of Oct.) have reached a distance of 9-10 km.
Backgound: Sierra Negre is the largest of the Galapagos volcanoes, with a caldera 10 km in diameter. Its last eruptino occurred in 1979; the lava flows of that eruption did not pose any significant risk to the population of the island.