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Thursday, May 19, 2022

Explained: What is the Pacific ‘Ring of Fire’?

The Hunga Tonga-Hunga Ha'apai volcano, which erupted over the weekend, lies along the Pacific ‘Ring of fire’.

Written by Aswathi Pacha , Edited by Explained Desk | Kochi |
January 19, 2022 1:10:37 pm
This satellite image provided by Maxar Technologies shows an overview of Hunga Tonga Hunga Ha'apai volcano in Tonga on Dec. 24, 2021.(Satellite image ©2022 Maxar Technologies via AP, File)

The Hunga Tonga-Hunga Ha’apai volcano erupted over the weekend, sending ash and smoke thousands of feet into the air. The volcano, situated on an uninhabited island, became active in 2009. It lies along the Pacific ‘Ring of fire’, and is just over 60 kilometres from the island nation of Tonga.

The Pacific ‘Ring of Fire’ or Pacific rim, or the Circum-Pacific Belt, is an area along the Pacific Ocean that is characterised by active volcanoes and frequent earthquakes. It is home to about 75 per cent of the world’s volcanoes – more than 450 volcanoes. Also, about 90 per cent of the world’s earthquakes occur here.

Its length is over 40,000 kilometres and traces from New Zealand clockwise in an almost circular arc covering Tonga, Kermadec Islands, Indonesia, moving up to the Philippines, Japan, and stretching eastward to the Aleutian Islands, then southward along the western coast of North America and South America.

The area is along several tectonic plates including the Pacific plate, Philippine Plate, Juan de Fuca plate, Cocos plate, Nazca plate, and North American plate. The movement of these plates or tectonic activity makes the area witness abundant earthquakes and tsunamis every year.

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Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire. The trenches are shown in blue-green. The volcanic island arcs, although not labelled, are parallel to, and always landward of, the trenches. For example, the island arc associated with the Aleutian Trench is represented by the long chain of volcanoes that make up the Aleutian Islands. (Source: W. Jacquelyne and Robert I. Tilling via USGS)

Along much of the Ring of Fire, tectonic plates move towards each other creating subduction zones. One plate gets pushed down or is subducted by the other plate. This is a very slow process – a movement of just one or two inches per year. As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity.

In the case of Tonga, the Pacific Plate was pushed down below the Indo-Australian Plate and Tonga plate, causing the molten rock to rise above and form the chain of volcanoes.

Subduction zones are also where most of the violent earthquakes on the planet occur. The December 26, 2004 earthquake occurred along the subduction zone where the Indian Plate was subducted beneath the Burma plate.

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