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Volcanoes of Terceira, in the Azores Islands

38.7N 27.2W

September 11th, 2009 Category: Volcanoes

Azores Islands - September 3rd, 2009

Azores Islands - September 3rd, 2009

The Azores (Açores) Islands are an archipelago in the Atlantic Ocean belonging to Portugal. There are nine major Azorean islands, with a total area of 2,346 km2 (906 sq mi), and eight smaller islets known as “Formigas”, all of which have volcanic origins.

This orthorectified image shows four of the islands (clockwise from the botto left):  Pico Island (partially visible), São Jorge, Graciosa and Terceira.

Terceira Island, visible in its entirety, consists of four overlapping stratovolcanoes built above a geologic rift called the Terceira Rift. The volcanos rise from a depth of over 1,500 metres (5,000 ft) on the floor of the Atlantic Ocean.

The oldest at over 300,000 years is the Cinquo Picos stratovolcano that forms the eastern part of the island, with a 7 km (4 mi) diameter caldera which is one of the largest in the Azores.

Next in age at perhaps 100,000 years is the Guilherme Moniz stratovolcano in the south-central part of the island, which also has a caldera with the highest remaining point on the rim reaching 623 metres (2,044 ft).

Just to its north is the Pico Alto stratovolcano, probably less than 60,000 years old. It once had a caldera too, but subsequent eruptions filled it with several smaller lava domes and cones which top out at 808 m (2,651 ft).

The youngest and only historically active volcano is Santa Bárbara, which comprises the western end of the island and is its highest point at 1,023 m (3,356 ft). This stratovolcano is truncated by two calderas, the youngest of which formed about 15,000 years ago.

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