The Sierra Negra volcano on Isabela Island in the Galapagos erupted Tuesday morning. The largest volcano in the Galapagos island chain, Ecuador’s Geophysical Institute (IG) says the eruption poses no immediate threat to human life on Isabela Island although about 50 people living near the mountain were evacuated as a precautionary measure.
Scientists have warned for months that Sierra Negra was building toward an eruption, citing an increase in earthquakes and satellite images showing rising temperatures under the caldera. Just before Tuesday’s eruption, the IG recorded earthquakes measuring 4.5 and 3.8 on the Richter scale.
In a Tuesday night bulletin, the IG said that lava was observed flowing inside crater and on the mountain’s north flank and that an ash and gas cloud was rising above the volcano. It said it expected a moderate eruption but said this could change. “There is no danger at moment to Puerto Villamil [Isabela Island’s largest community, population 1,200] but we are monitoring the strength of the eruption carefully.”
Sierra Negra is notable for the size of its crater, measuring six by four miles, one the largest in the world among active volcanoes. Geologists say that the volcano experienced massive eruptions on several occasions over the past 300,000 years, at least two of which had magnitudes that affected weather world-wide.
The last eruption in recent history was in 2005.
The Sierra Negra eruption follows that of the Cumbre volcano on neighboring Fernandina Island two weeks ago. Cumbre remains active but its lava flow into the ocean has decreased significantly, the IG reports.