La Cumbre volcano on Fernandina island, one of the youngest in the archipelago, began erupting Sunday evening, Galapagos National Park (PNG) officials said in a statement.
The 1,467 metre high (4,813 feet) volcano has a crack along its south-eastern flank and "a lava flow descends to the coast", PNG added.
The island is home to a number of species including iguanas, penguins, flightless cormorants, snakes and an endemic rat, and has "very important" ecological value, PNG said.
Before the eruption, an earthquake with a magnitude of 4.7 was felt, according to the local Ecuadorian Geophysical Institute, followed by 29 aftershocks.
The volcano also erupted in June 2018.
The unique fauna of the UNESCO-listed Galapagos Islands -- located 1,000 kilometres (620 miles) east of mainland Ecuador -- helped English naturalist Charles Darwin develop his theory of evolution by natural selection.
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