The birth of a new island

The birth of a new island

The Tonga archipelago is again richer by a small island. Whether this volcanic island will remain permanently, however, is questionable.

On January 15, 2022, the Hunga Tonga-Hunga Ha'apai exploded in the Pacific Ocean - and the Tonga archipelago was once again one island poorer; only a few rocky peaks still protrude from the sea. But the island arc near the Tonga Trench, on which Tonga and other islands lie, has the highest density of underwater volcanoes on earth. One of them erupted on Sept. 10 and has since created a new islet on Home Reef, according to NASA satellite imagery.

On September 11, the volcano broke through the water line, while at the same time the sea in its vicinity turned greenish due to the eruption material: Sulfur compounds and released acids additionally ensure that the water here has a very low pH value, at least for the time being. According to estimates by the Geological Survey of Tonga, on September 14 the island already had an area of 4000 square meters and a height of about ten meters above sea level.

Home Reef is located on the Kermadec-Tonga subduction zone, where three earth plates meet. Here, the Pacific Plate subducts beneath two other plates, with the fastest subduction known in the world occurring on the eastern side of the Tonga Plate: At a rate of 24 centimeters per year, crustal material disappears into the depths here; its melting promotes active volcanism in the region. At the same time, the second-deepest deep-sea trench on earth is located here, which is up to 10,000 meters deep.

Islands have appeared on Home Reef four times since the first records began, but they usually lasted only a short time. In one case at a neighboring volcano, however, the mainland even survived for 25 years. Often the surge causes the islands to disappear again, as the volcanic loose material can be quickly eroded away. In other cases, further destructive eruptions cause the new land to sink back into the sea. The future of the new island at Home Reef is therefore uncertain - and rather short.a

Alex A


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