South Atlantic Ocean
37.09 S, 12.28 W
summit elevation 2060 m
Tristan da Cunha Island is a British Overseas Territory in the south Atlantic. The territory consists of the main island, Tristan da Cunha (area: 98 sq km ), Inaccessible Island, Nightingale Islands, and Gough Island.
Tristan da Cunha was discovered in 1506 by the Portuguese Admiral, Tristao
d'Acunha, after whom it is named, and Gough Island by another Portuguese, Goncalo Alvarez, at about the same time. Nightingale is named after Captain Gamaliel Nightingale, R.N., who visited the area in 1760.
The site of the 1961 eruption occasionally emits vapour, and there are occasional earthquakes. Tristan da Cunha is a hotspot volcano, and is located 400 km east of the Mid-Atlantic Ridge. The island has many well-preserved volcanic cones and scoria mounds. Explosion craters, lava levees and lava channels also occur.
Between Tristan and the two smaller islands, the water reaches a depth of 8000 ft.
Shape of the Island
Tristan consists of a central cone 6760 ft. high, containing a small crater lake. On the flanks of the main cone are small parasitic ash and lava cones, rising to a maximum height of 600 ft. above the surroundings. The outer slopes of the main cone are truncated by a ring of cliffs around the island ranging from 1000 to 3000 ft. above sea-level.
August 2004 Earthquakes
A swarm of earthquakes occurred beneath Tristan da Cunha during the nights of 28 and 29 July 2004. The main swarm lasted about 8 hours and occurred 30 km below the volcano.
Tristan da Cunha volcano erupted on 10th October 1961 after two months of seismic activity. A lava dome was extruded, about 300 m east of the island settlement, on the north coast of Tristan da Cunha. Between 20th and 27th October the seaward side of the dome collapsed, followed by extrusion of lava.
Red glow from a lava mound was first observed at 2am on 10th October 1961. By daybreak the mound had developed into a dome 60 ft high and 150 ft in diameter. It continued to grow throughout the day. Lateral expansion was caused by the accumulation of blocks, which broke loose from near the summit and rolled to the base. The active cone reached a height of 250 ft by 15th October. On 21st October the main beach of Tristan da Cunha was almost covered with lava. A lava flow moved towards the first house on the eastern side of the island. The erupting cone had reached nearly 400 ft. high. on 27th October lava reached 100 m into the sea where it was steaming vigorously.
There were no observations of the activity at Tristan da Cunha volcano during November.
On 16th December, observations were made from a passing ship. Eruptive activity was more violent than previously observed. Every few minutes the volcano emitted a cloud of white smoke, accompanied by noise, and blocks and bombs were thrown 100 m into the air. The eruptions were accompanied by the emission of red flames or liquid 3 m or more above the summit. By 16th December lava extended 400 m beyond the former coastline and was about 1 km wide at its seaward margin.
At the end of January 1962 a lava dome began forming. At its peak growth at the beginning of February, numerous avalanches swept down its flanks, accompanied by clouds of dust and glowing blocks. No explosions occurred at the dome. Fumarolic activity declined throughout February and March and thin columns of vapour continued to rise from a few fumaroles on the lava field.
The eruption of Tristan da Cunha forced the temporary evacuation of the entire population of the island.