Psalm 104:32 says God “touches the mountains and they smoke!” That’s talking about volcanos. But the verse could also say God “touches the undersea mountains and they smoke!” Submarine volcanos put on quite a show too. We are only beginning to figure them out. Being thousands of feet below the ocean makes them hard to study. But scientists guess that there are more than a million volcanos under the sea—far more than on land.

If you know some things about land volcanos, you have a good start on undersea volcanos. They usually occur along the edges of Earth’s tectonic plates. Imagine Earth as a pie with its crust cracked in big pieces. The pieces are always shifting. Some are bumping against each other or pulling apart. Some are rubbing sideways. And some plates are sliding under or over each other. The deep Earth is full of melted rock that is ready to escape. Earth’s cracked crust gives it an opportunity. 

Those things are true of volcanos undersea and on land. What makes submarinevolcanos interesting is all the different things that happen when lava comes in contact with sea water. Lava can ooze and form pillow shaped boulders or sheets of lava glass. Lava can also erupt into water suddenly, forming a frothy underwater cloud. It can harden into large and small chunks of rock. If you didn’t know that it was known as pumice, you might call it “sponge rock.” The gasses in lava leave lots of tiny air holes in it. When a cloud of pumice floats on the surface of the ocean, it is called a raft.

Interesting to know: Danger! Researchers have suggested that huge clouds of gas bubbles could actually cause a ship to lose buoyancy and sink. It’s like the ship is suddenly sailing on mostly air instead of water. Underwater volcanos could explain why some vessels have disappeared without a trace.