Some underwater volcanoes could erupt soon - should we be afraid?

Experts estimate that about two-thirds of all volcanoes on Earth are underwater. Hidden thousands of meters below the sea surface, they are home to many unknown species, and their eruptions can create new islands.

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Disclaimer: The translations are mostly done through AI translator and might not be 100% accurate.

04.08.2025. 07:36h

Underwater volcanoes are far from the eye, so many people don't even think about them.

However, recent warnings from scientists about possible eruptions in the near future have nevertheless attracted attention.

One of these warnings concerns a large underwater volcano called Axial Ridge, located about 480 miles (XNUMX km) off the coast of Oregon in the United States of America (USA).

Experts claim that this volcano is heating up and showing signs of a possible eruption within the next year.

Recent earthquakes on the Greek island of Santorini have also prompted scientists to study in more detail the caldera, a geological formation created when a volcano collapses in on itself, creating a large and distinctively shaped volcanic crater, as well as the nearby underwater volcano Columbo.

It is believed that these volcanoes may not erupt anytime soon, but that it is only a matter of time before it happens.

So, should we be afraid?

Hidden in the depths of the ocean

Volcanoes are openings in the Earth's crust through which hot ash, gases, and molten rock, also known as magma, erupt.

Many people usually imagine them as large mountains, like Vesuvius and Etna, from which huge flows of orange lava flow.

However, experts estimate that about two-thirds of all volcanoes on Earth are underwater.

Hidden thousands of meters below the sea surface, they are home to many unknown species, and their eruptions can create new islands.

D. Kelley, University of Washington/BOEM/NSF-OOI/WHOI, V19

Like those on land, underwater volcanoes can cause earthquakes and tsunamis, which sometimes have far-reaching consequences.

Thus, the eruption of the Hunga Tonga-Hunga Ha'apai volcano in the island nation of Tonga in 2022 caused a tsunami in the Pacific Ocean, and the waves reached Australia, New Zealand, Japan, as well as the western coasts of North and South America.

Three people died, hundreds of homes were damaged, and Tonga was cut off from the world for five weeks due to a ruptured undersea internet cable.

Where are underwater volcanoes located?

They mostly form in places where tectonic plates either separate or slide past each other, allowing magma to erupt to the surface from deep within the Earth's crust.

Since tectonic plates cover the entire planet, underwater volcanoes are found almost everywhere - from the Atlantic and Pacific Oceans to the Mediterranean Sea.

Sometimes hot jets of magma rise through parts of a tectonic plate, forming volcanoes.

Different eruptions

Dr Isobel Yeo, an expert on underwater volcanoes at the UK's National Oceanography Centre, explains that the interaction of magma and water makes underwater volcanic eruptions different from those on land.

"Imagine throwing water on a hot pan - it will evaporate immediately."

"The same reaction occurs in shallow volcanic systems," she says, explaining that this refers to volcanoes that are located a few hundred meters below the sea surface.

In deeper underwater volcanoes, the explosive reaction is absent due to water pressure.

These volcanoes also spew magma, but it cools quickly, says Yeo.

The amount of gases in the magma also determines the strength of the eruption - the greater the amount of gases, the more powerful the eruption, experts say.

How often do underwater volcanoes erupt?

It is difficult to determine the exact number of underwater volcanoes and the frequency of their eruptions, because most of them are rarely and irregularly monitored, says Dr. Yeo.

Experts point out that monitoring underwater volcanoes is very expensive for several reasons, such as the cost of the required technology, submarines and ships, and the difficulty of conducting activities in remote parts of the ocean.

Some scientists estimate that there are thousands of underwater volcanoes around the world, while others believe there may be as many as a million.

These opinions are based on complex mathematical calculations and the fact that about 70 percent of the Earth's surface is covered with water.

"There are only a few places in the world where detailed measurements of these systems are being made," says Professor Deb Kelly, a marine geologist at the University of Washington in the US.

Which islands are of volcanic origin?

The Hawaiian Islands are a chain of volcanic islands that, according to experts, began to form about 70 million years ago.

Experts believe they were formed by magma under the ocean continuously rising and erupting above sea level.

And unlike Hawaii, the island of Santorini in the Aegean Sea was created by a massive eruption around 1630 BC, according to the US National Oceanic and Atmospheric Administration (NOAA).

Another famous island that was formed by volcanic activity is Iceland.

"But there are actually many places around the world where volcanic islands can be found."

“If you go somewhere and the sand is black, it’s probably volcanic,” says Yeo.

Jose Sarmento Matos/Bloomberg via Getty Images

Underwater volcanoes regularly create new land surfaces.

For example, an underwater volcano eruption in 2023 created a new island not far from the island of Iwo Jima near Japan.

However, such new islands sometimes erode and disappear under water.

"We're likely to see new islands being created, but we're also likely to see some of them disappearing," says Dr. Yeo.

More than a volcano

Monitoring underwater volcanoes is important for better understanding marine ecosystems, emphasizes Professor Kelly.

"These volcanoes are like oases on the seafloor, so they have incredible biological communities associated with them."

"Sometimes you can't see the rocks because they're covered in animals," she explains.

Kelly adds that more data about these environments would help make responsible decisions about activities such as deep-sea mining.

"It's really important to know what kinds of organisms are there, how they affect the rest of the ocean, how long they survive, and that kind of information is needed before you dig them up," she points out.

Should we be worried?

All volcanoes, whether on land or under the sea, can pose a hazard, Yeo points out.

"I don't think we should be more worried about underwater volcanoes than we are about others," she says.

"But I think we should monitor them equally, which we don't currently do."

In April, tourists and locals were evacuated due to a volcanic eruption in Iceland.

"I think such evacuation should also be possible for underwater volcanic eruptions," says Yeo.

Monitoring underwater volcanoes is important not only because of the dangers associated with an eruption, but also because parts of the volcano can break away underwater, which can cause tsunamis, she adds.

What about the Axial Ridge volcano?

Professor Kelly is involved in monitoring an underwater volcano called the Axial Ridge, whose base is located about 2.600 meters deep in the Pacific Ocean.

He says the volcano is monitored via a cable nearly 500 kilometers long, stretching from the coast to the volcano itself.

Thanks to this, scientists have noticed that the volcano is heating up and has already passed the swelling points of its previous eruptions, says Professor Kelly.