This normally submerged volcano was reported to be in eruption on June 6, 1995. The New Zealand Hydrographic Office issued a warning for ships in the area to be careful. By June 21 continuing eruptions had built a small island 50-80m high and covering sev eral acres. A 200-500m wide cinder cone is forming with ash and steam shooting hundreds of meters into the air.
The Tonga Islands are a line of volcanoes 2000 or so kilometers east of Australia. The volcanoes mark a long zone of subduction where part of the Pacific Plate is being carried deeply down into the Earth's mantle. The Tonga Islands include the 150 actual islands, but there are many submerged volcanoes which someday may grow into islands. This Pacific nation is getting bigger all the time!
The Metis volcano was first noticed to have risen above the ocean's surface in 1851, but ocean currents quickly eroded the new island down. Later eruptions built other islands over the shoals, most recently in 1969. Sometimes undersea eruptions of Metis c reate huge rafts of lightweight pumice that float hundreds of kilometers. The temporary islands are simple cinder cones which are easily destroyed by ocean waves. Sooner or later a cinder island will be covered by hard lava flows and will be resistant to the wave. Someday a permanent island will be formed. Will these 1995 eruptions do it?
Brad Scott, Manager Volcano Surveillance, Inst. of Geological and Nuclear Science, New Zealand
Bryan, WB, GD Stice & A Ewart (1972) Geology, petrography and geochemistry of the volcanic islands of Tonga. Journal of Geophysical Research 77, 1566-1584.