Why Was The Volcano Explosion in Tonga So Violent, And What to Expect Now?

A violent eruption of an underwater volcano on January 15 has spread shock waves around the world, even though the Kingdom of Tonga doesn't attract global attention.

The volcano is usually uninteresting to look at. The islands are located north of Nuku'aloFA and poking about 100 meters above sea level. The volcano is 20 kilometers wide and is around 6,000 feet high.

Over the past few decades, the volcano has erupted frequently. During the years of 2009 and 2014/15 hot jets of magma and steam exploded through the waves. The eruptions were small anddwarfed by the January events.

Our research shows that the volcano is capable of producing large eruptions every thousand years.

Satellite imagery of the volcanic eruption in Tonga.
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The atmospheric shock wave caused a brief spike in air pressure at our climate stations.
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January 15, 2022, NIWA Weather.

Sea water should cool the volcano's magma down, so why are the eruptions so powerful?

A thin film of steam can form between the magma and the water if it rises slowly. The outer surface of the magma can be cooled by providing a layer of insulation.

When volcanic gas is blasted out of the ground, this process doesn't work. When magma enters the water quickly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.

The "fuel-coolant interaction" is similar to weapons-grade chemical explosions. The magma is torn apart by violent blasts. A chain reaction begins, with new magma fragments exposing hot interior surfaces to water, and the explosions repeat, eventually jetting out volcanic particles and causing blasts with supersonic speeds.

There are two scales of eruptions.

The two old Hunga islands were joined to create a 5 kilometer island. The historical eruptions were just curtain raisers to the main event.

We found a hidden caldera 150 meters below the waves.

The volcanic cones and massive caldera are shown on the map. The person isShane Cronin.

The caldera is a depression around 3 miles across. Small eruptions occur at the edge of the caldera, but big eruptions come from the caldera itself. The caldera is deepened by the large eruptions of the top of the volcano.

The chemistry of past eruptions suggests that the small eruptions are a sign that the system is about to explode.

There are deposits on the old islands that have evidence of two big eruptions from the Hunga caldera. The last big caldera eruption was 1100CE, and we used radiocarbon dates to show that big caldera eruptions have been occurring for over a thousand years.

The eruption on January 15 seems to be on time.

What will happen now?

The island is currently obscured by ash clouds and many aspects of this major eruptive sequence are still unclear.

The eruptions on December 20 and January 13 were moderate in size. They created clouds of up to 17 kilometers elevation and added land to the island.

The scale of violence has gone up. The ash is about 12 miles high. It spread out over a distance of about 130 kilometers from the volcano before it was distorted by the wind.

The National Oceanographic and Atmospheric Administration.

This shows a huge power that cannot be explained by water alone. It shows that the caldera has erupted with fresh, gas-charged magma.

The eruption produced a large wave in the region. Waves were seen from space and recorded in New Zealand. After the eruption began, the sky was blocked out and ash began to fall.

The signs suggest the caldera has awoken. During an explosion, coupled atmospheric and ocean shock waves are generated, but they are also caused by submarine landslides and caldera collapses.

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January 16, 2022.

It's not clear if this is the end of the eruption. A major pressure release may settle the system.

There is a warning in the geological deposits from the volcano's previous eruptions. Each of the major caldera eruption episodes involved many separate explosion events.

We could be in for several weeks or even years of volcanic unrest from the volcano. I hope not for the sake of the people of Tonga.

Professor of Earth Sciences, University of Auckland, was named.

The Conversation's article is a Creative Commons licensed one. The original article can be found here.