Submarine volcanoes, or ‘underwater volcanoes’ are they are sometimes called, are vents or fissures located underwater, on the surface of the earth. These underwater volcanoes act just like those on land. They can erupt and produce magma. Amazingly, some of the biggest individual volcanoes and the biggest volcanic chain are located in the oceans. They are the most common at divergent plate boundaries or areas where tectonic plates are separating. The plate movement is incredibly important in determining what type of volcano is formed. This holds true for volcanoes on land, also known as subaerial volcanoes.

Footage of a submarine volcano erupting

One of the most famous submarine volcanoes is Krakatoa, located between Java and Sumatra. Krakatoa erupted in 1883 to devastating consequences. The eruption and the resulting tsunami killed more than 36,000 people. Over 70% of the Krakatoa island and the archipelago were destroyed. It is now noted as one of the deadliest volcanic eruptions in recorded history. It was so loud that the explosion was heard up to 1,930 miles (3,110 km) away in Australia. Ships as far away as South Africa were impacted by tsunamis. There are thought to have been caused by the entry of pyroclastic flow into the sea. Following the eruption, seismic activity flourished for the next year.

Where are Submarine Volcanoes Located?

The majority of submarine volcanoes are located near mid-ocean ridges. These are areas of tectonic plate formation and hydrothermal vents. The vents are created and maintained through the volcanic heat and can be found all around the world. Although it seems like it might be an easy process, locating these immense volcanoes, it’s not quite so easy. Scientists use a CTD package that measures various ocean temperature changes, conductivity, and depth. These readings help them identify specific changes that might signify a hot spring under volcanoes in the process of erupting. Some of the signs include the temperature and the cloudiness of the water.

Scientists also use hydrophones to seek out erupting volcanoes. These are microphones designed to be used underwater, and, if the volcano is close enough and not too deep, it can pick up the sound of boiling water.

How are Submarine Volcanoes Different?

The presence of water in and around a volcano changes the way that it acts. At volcanic sites, seawater runs into the seafloor, entering through cracks. There, it is heated by the molten rock. This results in a chemical reaction in which the seawater is changed into a hydrothermal fluid. The fluid is propelled back into the ocean, creating a hydrothermal vent.

When a volcano erupts, the presence of water means that the magma will cool much faster than it would on land. It is, in fact, sometimes transformed into volcanic glass. Volcanic class is a product of the rapidly cooling magma. There are a variety of different types of volcanic glass. These include pumice, tachylite, palagonite, Pele’s hair, Limu o Pele, and Sideromelane. In general, lava takes different shapes and forms when it cools underwater.

As soon as the lava touches the water, a crust forms around it, creating what is known as pillow lava. It takes its name from the pillow-shaped forms that are created as a result of the crust forming. They are usually around one meter in diameter and made out of basalt. They might also be formed of komatiite, boninite, rhyolite, and more. Pillow lavas are used to confirm volcanic activity throughout the ages of the Earth.

Pillow lava from an underwater/submarine volcano
Pillow lava

Volcanic eruptions vary depending on the depth of the water as well. For example, if the eruption occurs in excess of the critical pressure of water, then it becomes a supercritical fluid. This refers to a substance created at a temperature/pressure beyond its critical point, where phases of liquid and gas do not exist. But below the pressure required to create a solid. This is only one of several reasons why it’s difficult for scientists to find and study these eruptions. Without the sound of boiling water, hydrophones are useless at great distances.

Submarine Volcanoes in the Ring of Fire

The most famous collection of underwater volcanoes is part of the Ring of Fire. It is an area in the basin of the Pacific Ocean in which an unusually high number of eruptions and earthquakes occur. In the ring, there are volcanic arcs and belts, as well as plate movement. There are in total of 452 volcanoes present in the ring. The ring also plays host to round 90% of the world’s earthquakes and 88% of the world’s largest volcanic eruptions.

The Havre Submarine Volcano

One of the most notable eruptions of a submarine volcano occurred in 2012 when for ninety days lava spewed from fourteen events around the opening of Havre. It is located 3,000 feet, (900 meters) below the surface of the Pacific Ocean. It is one of the world’s largest and its eruption in 2012 is the largest deepwater eruption ever recorded. As reported by Smithsonian, scientists have compared the eruption in size and result in the eruption of Mount St. Helens in 1980 in Washington State.

But, very much unlike the Mount St. Helens eruption, Havre occurred far from the public spotlight. The eruption was discovered by a passenger on a commercial flight who noted a discolored patch of water in the ocean. After sending an email, a search got underway to discover the cause of this discolored patch of water. The Smithsonian also reported that about 75 percent of the lava created by Havre made it to the surface. A larger chunk of pumice was revealed to be the source of the discoloration. Pieces of pumice, like those created by Havre, are at first buoyant. They then become saturated with water and sink to the seafloor.

Submarine Volcanoes and Sea Life

Scientists have discovered that marine life is often attracted to and thrives around the sight of volcanic eruptions. Specifically, while researching volcanos near Guam, scientists discovered a notable increase in the population of animals that live on top of the volcano. These include shrimp, crabs, and barnacles. These animals thrive in the intense, chemical-filled conditions that exist on top of the underwater volcanoes, taking nourishment from the eruptions. One specific shrimp has adapted special claws used to harvest food.

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