A Moment of Science

Are Underwater Volcanoes Stifled By Water?

When volcanoes erupt underwater, do the waves and ocean currents help calm the eruption?

volcano erupting

Photo: Ben Beiske (Flickr)

Volcanic eruptions can happen above and below water.

Firefighters use water to battle a towering inferno. You might wonder if water could also stifle an erupting volcano.

Actually, this experiment happens every time a volcano erupts at the bottom of the ocean.

What Happens When A Volcano Erupts Underwater?

Most of the world’s volcanic action happens an average of eight thousand five hundred feet underwater. Deep beneath the waves there are an estimated one million volcanoes.

As with land volcanoes, molten lava pushes up from beneath the sea floor at thousands of degrees Fahrenheit. Ocean water can’t “put out” the volcano the way firefighters put out a fire, but it does have a profound effect on what happens to the lava once it’s out of the ground.

Water’s Pressure

The biggest difference between undersea and land volcanoes has nothing to do with water’s wetness, but with its pressure.

At these depths, the water pressure can be two hundred and fifty times more powerful than air pressure at the Earth’s surface. This prevents bubbles from forming in the lava, eliminating the likelihood of an explosive eruption like some land eruptions are.

Glassy, Rock Formations

Instead, lava squeezes out of the ground like toothpaste out of a tube, forming glassy rock formations that look like long, stacked pillows. The pressure is so high that steam never even forms where lava touches water. You could be in a boat over a giant, erupting volcano, and never even know it was there.

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