- 3421 - VOLCANO - Tonga January 2022! The volcano is usually not much to look at. It consists of two small uninhabited islands, Hunga-Ha’apai and Hunga-Tonga, poking about 100 meters above sea level 65 kilometers north of Tonga’s capital Nuku‘alofa. But hiding below the waves is a massive volcano, around 1800 meters high and 20 km wide.
--------------------- 3421 - VOLCANO - Tonga January 2022!
- Kingdom of Tonga witnessed a violent eruption of an underwater volcano on January 15, 2022. The eruption has spread shock waves around half the world.
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- The volcano has erupted regularly over the past few decades. During events in 2009 and 2014/15 hot jets of magma and steam exploded through the waves. But these eruptions were small, dwarfed in scale by the January, 2022 , events.
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- Why are the volcano’s eruptions so highly explosive, given that sea water should cool the magma down? If magma rises into sea water slowly, even at temperatures of about 1200 degrees, a thin film of steam forms between the magma and water. This provides a layer of insulation to allow the outer surface of the magma to cool.
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- But this process doesn’t work when magma is blasted out of the ground full of volcanic gas. When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.
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- This “fuel-coolant interaction” is akin to weapons-grade chemical explosions. Extremely violent blasts tear the magma apart. A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.
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- The caldera is a crater-like depression around 5 km across. Small eruptions occur mainly at the edge of the caldera, but very big ones come from the caldera itself. These big eruptions are so large the top of the erupting magma collapses inward, deepening the caldera.
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- Radiocarbon dates show that big caldera eruptions occur about ever 1000 years, with the last one at AD 1100. The two earlier eruptions on December 20, 2021 and January 13, 2022 were of moderate size. They produced clouds of up to 17 km elevation and added new land to the 2014/15 combined island.
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- The latest eruption has stepped up the scale in terms of violence. The ash plume is already about 20 km high. It spread out almost concentrically over a distance of about 130 km from the volcano, creating a plume with a 260 km diameter, before it was distorted by the wind.
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- Scientists are racing to understand a puzzling series of massive ripples in Earth’s atmosphere triggered by the eruption of the Tongan volcano at the weekend. Satellite data shows that the event provoked an unusual pattern of atmospheric gravity waves. Previous volcanic eruptions have not produced such a signal, leaving experts stumped.
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- The discovery was made in images collected by the Atmospheric Infrared Sounder (AIRS), mounted on NASA’s Aqua satellite, in the hours after the eruption of the volcano on 14 January.
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- They show dozens of concentric circles, each representing a fast-moving wave in the gases of the atmosphere, stretching for more than 16,000 kilometres. The waves reached from the ocean surface to the ionosphere.
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- Atmospheric gravity waves occur when air molecules in the atmosphere are vertically, rather than horizontally, disturbed in the air column. This can happen as wind picks up speed as it rises over a mountaintop, or as a result of convection in local weather systems.
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- The up-and-down waves transfer energy and momentum through the atmosphere, and often show their effects in the way in which they cause high clouds to form in a series of ripple. The Aqua satellite show dozens of concentric circles, which are fast-moving atmospheric waves.
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- The rapid updraft of hot air and ash from an erupting volcano into the upper atmosphere could trigger gravity waves on a much larger scale. But nothing like this has been observed with previous eruptions analyzed since the AIRS instrument was launched in May 2002.
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- The eruption was heard across the South Pacific, and even in parts of the United States. Ash has covered many regions of Tonga, but a loss of power, phone lines and Internet connectivity has made it difficult for aid agencies to assess the extent of injuries, fatalities and damage.
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- This eruption seems to have been over in minutes, but it was explosive and it’s that impulse that is likely to kick off some strong gravity waves. Gravity waves can interfere with a cyclical reversal of wind direction in the tropics.
Researchers in New Zealand are closely monitoring the volcano for further eruptions. The volcano could be resupplied with large amounts of magma from deep underground and produce more explosive eruptions. But, if it has exhausted its main supply, it might produce only smaller eruptions, largely hidden beneath the surface of the ocean.
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- The eruption also produced a tsunami throughout Tonga and neighboring Fiji and Samoa. Shock waves traversed many thousands of kilometers, were seen from space, and recorded in New Zealand some 2000 km away. Soon after the eruption started, the sky was blocked out on Tongatapu, with ash beginning to fall.
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- Tsunami are generated by coupled atmospheric and ocean shock waves during an explosions, but they are also readily caused by submarine landslides and caldera collapses.
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- In geological deposits from the volcano’s previous eruptions. These complex sequences show each of the 1000-year major caldera eruption episodes involved many separate explosion events.
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January 20, 2022 VOLCANO - Tonga January 2022! 3421
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