It may sound surprising, but many mountains are hiding from us—some of which may be more than a mile high. Scientists are finding more of them all the time, though—at the bottom of the sea. A research cruise in 2023, for example, found four of them in the Southern Ocean.

The scientists were studying the Antarctic Circumpolar Current, which circles around Antarctica. It’s the strongest ocean current in the world. It prevents most of the warm water from the other oceans from reaching Antarctica. But some warm water sneaks through. That makes the Antarctic ice melt faster, speeding up the rise in global sea level.

Researchers were looking for these “leaks,” and studying how the warm water was flowing around Antarctica. As part of their work, they used sonar to scan a 7700-square-mile patch of the ocean floor. They also used an orbiting satellite to look for small “bumps” on the surface that indicate the presence of mountains.

They found a chain of eight mountains, called seamounts. They’re extinct volcanoes that formed within the past 20 million years. Some of them were already known, but four had never been seen before. The tallest is almost a mile high.

The mountain range is in the middle of the Antarctic Circumpolar Current. As the current flows over and between the mountains, it forms turbulent patches that break off as eddies. Those whorls can disrupt the current, allowing warmer water to punch through—helping thaw out the frozen south.