Hotspot volcanoes

Tonga Tsunami: What Are Underwater Or Submarine Volcanoes And How They Erupt

New Delhi: On Saturday January 15, an explosive eruption of the Hunga Tonga-Hunga Ha’apai volcano occurred, triggering a tsunami in the Pacific Ocean. The Undersea Volcano, also called Undersea Volcano, is located in the South Pacific kingdom of Tonga, an archipelago of more than 170 islands in the South Pacific Ocean 2,000 km northeast of Auckland, in New Zealand.

The Geostationary Operational Environmental Satellite (GOES), a joint operation between NASA and the National Oceanic and Atmospheric Administration (NOAA) in the United States, captured the explosive eruption of the submarine volcano located in Tonga, NOAA reported on its website.

Following the eruption of the underwater volcano, a tsunami occurred in Tonga and several South Pacific islands, according to media reports. Waves began to crash into coastal homes and telephone and internet connections were cut.

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The eruption had a radius of 260 km or 161.5 miles and sent ash, steam and gas 20 kilometers into the air, according to NOAA. It was about seven times more powerful than the previous eruption which occurred on December 20, 2021.

Additionally, a tide gauge in Nuku’alofa, Tonga’s capital, measured a 30cm or one foot tsunami wave resulting from the blast.

Types of underwater volcanoes and causes of their eruption

Submarine volcanoes are volcanoes located below the surface of the ocean. The explosion hurls rocks and ash into the water, and molten lava glows underwater. There are three ways in which underwater volcanoes can take place.

Underwater volcanoes can form due to rift zones found in all major ocean basins on Earth. The second type of submarine eruption occurs due to the collision of crustal plates. There is also a third type when an underwater eruption occurs as a result of a magma plume rising through the earth’s crust overlying a melt zone in the earth’s mantle.

Earth’s major ocean basins have rift zones, where crustal plates form. Underwater volcanic eruptions are characteristic of these rift zones, according to NOAA. Rift zones, also known as seafloor spreading centers because tectonic plates are moving away from each other in these regions, are mostly found at depths greater than 2,000 meters or 1.2 miles.

These are also called divergent plate boundaries.

Therefore, about three quarters of all volcanic activity on Earth occurs as deep submarine eruptions. This accounts for over 70% of all volcanic eruptions on Earth. The effects of these deep eruptions cannot be seen from the surface of the ocean because they are obscured by thousands of feet of water.

Underwater volcanoes play an important role in maintaining the ocean ecosystem. When central or submarine volcanic eruptions propagate, they produce a rock called basalt, which is the main rock constituting the ocean trust.

The eruptions that propagate on the seabed are mostly local. However, the earth’s crust can be deformed as a result of these eruptions. These deformations could closely resemble the eruptions of Hawaiian volcanoes, according to NOAA.

Submarine basalt flows have a distinctive “pillow shape” and can also be smooth sheet flows, similar to basalt eruptions on land.
Although submarine eruptions occur along all centers of seafloor spread, they are most common along spread centers where plates are moving apart at relatively rapid rates. For example, in seabed spreading centers such as the East Pacific Rise, spreading rates are 10 to 15 centimeters per year. Minimum spreading rates can be around one to two centimeters per year, seen in areas such as the Mid-Atlantic Ridge.

There are certain regions of the ocean known as subduction zones, where crustal plates collide and one plate gradually dips beneath the other and is eventually remelted. Submarine eruptions can occur in these subduction zones, or convergent plate boundaries. These submarine eruptions are different from those that occur along spreading centers.

What happens after an underwater volcano erupts?

While basalt rock forms as a result of underwater volcanic activity that takes place in rift zones, andesite rock forms due to subduction zone volcanism. Andesite is a melting product of the subducted plate. Andesitic lavas have a high viscosity and a high gas content, and therefore produce violent eruptions.

Scientists have only recently discovered and observed active deep andesitic eruptions. As these occur at significant depths, their explosiveness is mitigated.

When a magma plume rises through the earth’s crust covering a melt zone in the earth’s mantle, a different type of submarine eruption occurs. These eruptions are known as hotspot volcanoes and often form chains of volcanic islands and seamounts. These islands and seamounts are older with an increased distance from the surface location above the rising magma plume. Basalt rock is produced as a result of hot spot eruptions.

Underwater volcanoes are hidden beneath an average of 8,500 feet or 2,600 meters below the water surface. The global mid-ocean ridge system is estimated to produce 75% of the annual magma production.

Undersea volcanoes produce about 0.7 cubic miles or three cubic kilometers of lava, according to an article on the Oregon State University website. Magma and lava drive the edges of new oceanic plates and provide heat and chemicals to some of Earth’s most unusual and rare ecosystems.

It is estimated that there are more than one million underwater volcanoes, and up to 75,000 of these volcanoes are found more than half a mile above the ocean floor.

The rate of plate motion plays an important role in determining the type of volcano that forms and the rate of eruptive activity.
Underwater volcanoes occurring in subduction zones resemble their subaerial counterparts, the only difference being that the weight of the overlying water changes the style of eruption.

Some of Earth’s largest volcanoes are the result of hot spots, which leave linear seamount traces across ocean basins.

Ecosystems supported by submarine volcanoes

Underwater volcanoes create unique habitats, which makes them even more interesting. Seamounts, which are undersea mountains formed by volcanic activity, are areas of great biological diversity. Their shape helps deflect upward food-carrying currents and attract a variety of sessile fauna, as well as the crustaceans and fish that feed on them.

Scientists had discovered at the end of the 1970s that certain animals could even metabolize the inorganic compounds emitted during volcanic activity.

This forms unique communities around hotspots of hydrothermal venting, similar to the activity of geysers on land.

In 1977, hydrothermal vents and new lifeforms were first discovered on mid-ocean ridges, according to an article on the Oregon State University website. Hydrothermal vents, also called black smokers, are characterized by the presence of water, hydrogen sulphide and other minerals. The springs have temperatures of around 660 degrees Fahrenheit.

The warm waters are home to an ecosystem complete with giant clams, mussels, tube worms and other creatures that use sulfur, not sunlight, to live.

Vents from hydrothermal fluids produce black “chimney stacks” and are therefore called black smokers. Chimney stumps, made of iron and zinc sulfide and calcium sulfate minerals, can reach a height of about 40 feet, but most are less than 30 feet.

Following the submarine eruption of the East Pacific Rise, located in the Pacific Ocean, in 1991, hydrothermal vents have recently formed. These regions harbor colonies of tubeworms.