An eruption occurs once every thousand years .. Why was the eruption of the Tonga volcano so violent? What are the expectations of scientists?

All signs indicate that the supervolcano is active again, but it remains unclear whether this is the peak of the eruption or if we haven’t reached the peak yet.

in a article Published in “The Conversation” on January 15, Shane Cronin, Professor of Earth Sciences at the University of Auckland, reviewed the events of the eruption of the Tonga supervolcano, and discussed future possibilities for its continued activity.

On January 15, the enormous underwater volcano Tonga erupted in the Kingdom of Tonga in the Pacific Ocean, reaching a height of about 1,800 meters and a width of 20 kilometers, and led to the spread of strong tremors in half the world.

The volcano consists of two small uninhabited islands, Hunga-Ha’apai and Hunga-Tonga, about 100 meters above sea level and 65 kilometers north of Nuku’alofa, the capital of Tonga.

The volcano has been active over the past few decades, in 2009, 2014 and 2015, hot jets of magma and steam erupted through the waves, but those eruptions were small compared to the events of January 2022, which scientists found can occur about once every thousand years. .

Why are volcanic eruptions severe despite the presence of water?

If the magma rises into sea water slowly, even at temperatures around 1200°C, a thin layer of vapor forms between the magma and the water, providing a layer of insulation that allows the outer surface of the magma to cool.

However, this process does not succeed when magma erupts from the ground filled with volcanic gas, as the magma rushes into the water quickly, hindering the formation of vapor layers, bringing the hot magma into direct contact with the cold water.

Volcanologists call this the “fuel-cooling interaction” and it’s similar to chemical explosions used to make weapons, in which violent eruptions rupture the magma and a chain reaction begins. at supersonic speeds.

The volcano’s ash plume rose by about 20 km (Reuters)

The history of the eruption of the Honga volcano

The eruption of the Honga volcano in 2014 and 2015 created a volcanic cone that joined the two ancient islands of Honga to create a common island about 5 km long. Cronin explained that his team had been able to find evidence in sediments on ancient islands of two major volcanic eruptions in the past from Honga Crater.

They chemically matched these materials to volcanic ash deposits on the largest inhabited island of Tongatapu, and then used radiocarbon dates, and found that eruptions of large craters occurred about a thousand years ago, the most recent in 1100 AD. Thus, it appears that the eruption of January 15 was correct in time for the “Big Bang”.

What then?

We are still in the middle of this major volcanic sequence, and many aspects remain unclear, in part because the island is currently obscured by ash clouds. Previous eruptions on December 20, 2021 and January 13, 2022 were of moderate size and resulted in volcanic clouds 17 km high, and new land was added to the common island formed as a result of the 2014 and 2015 eruptions.

All signs indicate that the great volcano has returned to activity again (Reuters)

In the 2022 explosion, the ash column reached a height of about 20 km, and it is remarkable that it spread almost centrally at a distance of about 130 km from the volcano, forming a column with a diameter of 260 km before it was distorted by the wind, which indicates a huge explosive power.

The eruption also caused a tsunami throughout Tonga, neighboring Fiji and Samoa, and violent tremors swept thousands of kilometers, and were recorded in New Zealand, about two thousand kilometers away. Shortly after the eruption began, the sky was darkened at Tongatapu, and ash began to fall.

All of these signs indicate that the supervolcano has resurfaced, but it remains unclear whether this was the peak of the eruption, as geological deposits from previous eruptions show that each of the major thousand-year caldera eruption episodes contained many Discrete eruption events, and their activity can continue over weeks or even years, from major volcanic eruptions from Hunga-Tonga and Hunga-Hapai volcanoes.

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