Tonga Volcano Blast Was Unusual, Could Even Warm The Earth : Daily Current Affairs

Date: 26/09/2022

Relevance: GS-1: Important Geophysical phenomena such as earthquakes, Tsunami, and Volcanic activity;

Relevance GS-3: Environmental hazard and Disaster

Key Phrases: Volcanoes, Pacific ‘ring Of Fire’ Explosivity, Fuel-Coolant Interaction’, Caldera, Lightning, Meteotsunami, Tsunami

Why in News?

According to a study published in the journal Science, the deadliest volcano Hunga Tonga-Hunga Haapai which erupted in Tonga on 15 January 2022 injected millions of tons of water vapor high up into the atmosphere.
Now, scientists are trying to figure out how all that water could affect the atmosphere, and whether it might warm Earth’s surface over the next few years.

The eruption occurred about 500 feet underwater and the eruption of superheated molten rock also caused seawater to flash explosively into steam.
The blast extended for 162 miles (260 kilometers) and sent pillars of ash, steam, and gas soaring more than 12 miles (20 km) into the air, according to the National Oceanic and Atmospheric Administration (NOAA).
The researchers estimate that the eruption sent around 150 million metric tons of water vapor to the stratosphere, which is an amount equal to about 10 percent of the water already present there.

Big eruptions usually cool the planet as volcanoes send up large amounts of sulfur, which blocks the sun’s rays ultimately having a cooling effect on the atmosphere.
However, the Tongan blast had a greater amount of moisture since, the eruption started under the ocean, and thus, it shot up a plume with much more water than usual.

Increase in global temperature: Water vapor acts as a heat-trapping greenhouse gas, therefore, the eruption will probably raise temperatures instead of lowering them. However, the extent of warming is quite uncertain.
Depletion of the ozone layer: The extra water vapour that is the result of the eruption could influence atmospheric chemistry by boosting certain chemical reactions that could temporarily worsen the depletion of the ozone layer.
Heating up the earth’s surface: The Tonga eruption injected water vapour instead of sulphur molecules into the atmosphere, which is a strong greenhouse gas that traps heat. This means that the water vapour in the stratosphere could temporarily heat up the Earth’s surface. But this effect would dissipate when the extra water vapour cycles out of the stratosphere and wouldn’t noticeably exacerbate climate change effects.

The volcano, situated on an uninhabited island, became active in 2009.
It consists of two small uninhabited islands, Hunga-Haapai and Hunga-Tonga, about 100 m above sea level 65 km north of Tonga’s capital Nukualofa.
It lies along the Pacific ‘Ring of Fire’ and is just over 60 kilometers from the island nation of Tonga.
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.

It is an area along the Pacific Ocean that is characterised by active volcanoes and frequent earthquakes.
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.
It is home to about 75 percent of the world’s volcanoes i.e., more than 450 volcanoes.
Also, about 90 percent of the world’s earthquakes occur here.
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 with 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.

Volcanoes are vents in the Earth’s crust from which molten rock from below the crust erupts out onto the surface.
When below the surface, this molten rock is called magma.
When it is erupted or flows above the surface, it is called lava.
Volcanoes also release hot gases, fragments of rock, and ash.

Volcanic eruptions occur in a variety of ways and produce an equally varied set of landforms.
When two plates collide, the intense heat and pressure accompanying the collision lead to violent eruptions of lava from the opening that build up to form steep, cone-shaped volcanoes, called stratovolcanoes.
Conversely, when two plates pull apart, lava seeps through the space in between.
Under the ocean, this gentler flow of magma forms a crust on the seafloor.
Above ground, this creates wide, rounded shield volcanoes.
Volcanic eruptions may at times be so explosive and violent that the upper part of the volcano collapses, leaving behind a large pit called a caldera.

In the intensely high temperatures of the Earth’s core, some rocks melt and turn into magma.
Magma is less dense than the solid rock surrounding it, causing it to rise and collect in magma chambers.
The magma continues to rise through the lithosphere, and after some time reaches the Earth’s surface through vents and fissures.
In general, volcanic eruptions are caused by an increase in pressure in the lid of a volcano’s magma chamber.
In turn, magma is released through the volcano.
Volcanoes are often found in the boundaries of the Earth’s tectonic plates, which either move apart or subduct and crash into one another.

There is no specific difference between the formation of submarine (underwater) and subaerial (on land) volcanoes.
Most submarine volcanism is associated with the continuously active volcanism along mid-ocean ridges, where two tectonic plates are pulling apart.
The collision of two plates causes a volcano and if both tectonic plates are beneath the ocean, then the volcano will develop underwater.
Over time, they may grow to form volcanic islands.

Source: The Hindu

Mains Question:

Q. What is a volcano? How are volcanoes formed? Discuss the causes of volcanic eruptions. (150 words).