Gaua (also known as Santa Maria Island) is the largest of the Banks Islands in Torba Province of northern Vanuatu. It covers 342 km². It has rugged terrain, reaching up to Mount Gharat (797 m), the peak of the active stratovolcano at the center of the island. The most recent eruption was in 1982. The island was evacuated for four months in 1974 due to volcanic activity. The volcano has a 6 x 9 km caldera, within which lies a crater lake known as Lake Letas, the largest lake in Vanuatu. To the east of the lake is Siri Waterfall (120 m drop).
The Gaua volcano in far northern Vanuatu is on alert level 2.
The level was raised from one last week after a geo-hazard team confirmed an increase in seismic activity and sulphur gas.
Vanuatu's Department of Geology says the Mount Garet volcano is going through an eruptive phase that began on September 27.
It is recommended not to approach the volcano, especially within 10 kilometres.
Vanuatu citizens have been advised that rivers flowing down from the volcano may be hazardous because of potential mud-slides.
Volcanologist Philipson Bani travelled to the volcano to take measurements of sulphur dioxide.
He says that from a previous gas reading of nil, sulphur dioxide measured on October 3 was 3,000 tonnes - "so for this small volcano this is huge".
Two moderate earthquakes hit the South Pacific in quick succession on Monday.
A 5.3 magnitude tremor hit 285 kilometres from Santo, in Vanuatu at 0735 GMT, the US Geological Survey said.
It was followed minutes later by a 5.5 magnitude quake 214 kilometres from Apia, in Samoa.
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Gaua Island, Torba Province, Vanuatu
14.27 S, 167.50 E,
summit elevation 979 m
Shield Volcano
Gaua is a large shield volcano with gentle outer slopes, a large caldera lake (Lake Letas), and summit cinder cone (Mt Garet). The caldera is 8 x 6 km in diameter. Lake Letas occupies half the caldera with an area of 19.7 sq km. It is about 100 m deep and flat bottomed. There is warm, sulphur stained water near Mt Garet cone.
Gaua Island lies just north of the Santa Maria Fracture Zone, which runs perpendicular to the north New Hebrides Trench.
