Science

New island forms in Tonga after eruption of Home Reef volcano

New island forms in Tonga after eruption of Home Reef volcano
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Volcanic eruptions are nothing new in Tonga. Much of the Polynesian nation – an archipelago of over 170 islands – owes its existence to volcanic activity that gave rise to a chain of western islands thousands of years ago.

Home Reef, an active underwater volcano in the area, is the mother of a hand full from them. From time to time it spits out a mixture of lava, steam and ash which piles up – and boom, an island or sea hill is born.

That was the case earlier this month when a baby island poked through the water 11 hours after Home Reef erupted on September 11. 10, NASA recently announced press release. It started at about one hectare but has grown to about 8.6 hectares in a matter of days due to the volcano’s recent eruption wave Geological Surveys of Tongaa government agency.

while the word Iceland may evoke images of sandy beaches and lush vegetation, that’s not quite the case with these volcanic islands.

“It’s more like a big layer of ash, steam and pumice over the ocean,” Rennie Vaiomounga, a geologist with Tonga Geological Services, told the Washington Post. That means the new island isn’t even stable enough to walk on, although that could change if it stays long enough to solidify.

Eruptions in Home Reef — in the Tonga-Kermadec subduction zone, one of the world’s most active volcanic arcs — have often spawned new landmasses. But the sporadic appearance of the resulting islands is something of a “geological mystery,” Vaiomounga said.

“We never know when the island will appear or when it will disappear,” he said.

Tonga volcano has thrown an unprecedented amount of water into the atmosphere

It can take centuries, decades, or sometimes just a few years for a volcano to erupt and form an island. The first recorded explosion at Home Reef took place in 1852. Five years later it erupted again. In both cases small islands were produced, but they were transient. Accordingly, the same thing happened again in 1984 and 2006 Smithsonian Institution Global Volcanism Program.

Each time the small islands take on a different shape. The 1984 one — which was just over 185 acres tall — looked like a rectangular cheese board, with handles and all. In 2006, the island that formed more closely resembled one thumbs sticking out of the waterwith the rounded hill developing cliffs at least 164 feet high.

This time is the new island looks like an almost perfectly circular mole, sticking out about 49 feet above the sea surface. Its surface is large enough to accommodate 6½ standard soccer fields.

When volcanoes erupt, magma is shattered into tiny shards of glass that are shot into the air also known as ash, said Vaiomounga. When this mixture of broken minerals, glass, and rocks comes out of an underwater volcano like Home Reef, it drifts into the ocean.

A telltale sign of an underwater eruption is a pool of volcanic pebbles — or pumice — making the water surface look like a rocky beach, Vaiomounga added. Sometimes these minerals travel hundreds of miles away and eventually wash up on shore. But they can also build up and form an island.

How long the resulting island will survive is another question. The one from 2006, for example, sank until 2008, when the volcano’s summit plunged about 33 feet underwater, according to the Smithsonian Institution records. Late’iki volcano, also in Tonga, created an island that disappeared after two months in 2020. The same volcano had previously spawned an island that lasted for 25 years, according to NASA.

The ephemeral islands often don’t live long because erosion gnaws at them. The minerals that turn them into islands slowly return to the seabeds of their builders, which will then spit out new islands in the future — a geological cycle of life, Vaiomounga said.

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