Scientists have discovered thousands of new mountains — on the ocean floor

We're still discovering new mountains on Earth — thousands of them, in fact.

Back in August of 2014, scientists were mapping the ocean floor near the Johnson Atoll in the Pacific Ocean when they suddenly stumbled on an entirely new mountain that no one had ever seen before:

Three-dimensional view of the southwest side of the seamount with 23-degree slopes. (University of New Hampshire)

This seamount — as it's called — rose about 1,100 meters above the ocean floor (which itself was 5,100 meters below the surface). That's about the same height as Old Rag in Virginia. No one had ever noticed it before because this part of the Pacific Ocean hasn't been particularly well-explored.

"These seamounts are very common, but we don't know about them because most of the places that we go out and map have never been mapped before," explained James Gardner, research professor in the UNH-NOAA Center for Coastal and Ocean Mapping/Joint Hydrographic Center, who had led that mapping effort.

And is turns out, that was just the beginning.

It turns out there are thousands of undiscovered mountains

Now a new study this week in Science reveals another 15,000 new seamounts lurking on the ocean floor. That's in addition to the 5,000 or so that had previously been discovered.

A team of researchers at the Scripps Institution of Oceanography at UC San Diego used satellite measurements and gravity modeling to make the most detailed maps ever produced of the ocean floor. The map looks like this — trenches are in blue (click to enlarge):

(Scripps Institution of Oceanography)

most of the new mountains were 1,000 to 2,000 meters high — too small to be detected previously

About 80 percent of the ocean had never been mapped in this level of detail, and the researchers found all sorts of surprises. There was a spreading ridge in the Gulf of Mexico that was active 150 million years ago but is now buried in sediment.

And there were thousands of undiscovered seamounts on the ocean floor standing between 1,000 and 2,000 meters tall — mountains that were too small for previous satellite measurements to detect. These seamounts are typically conical volcanoes that are now inactive or extinct (and usually attract sea life).

So how did scientists make this new map? They took data from two satellites equipped with altimeters. These devices send microwave pulses to the ocean's surface and record how long it takes for the pulse to come back. Altimeters can measure all sorts of things (like sea-level rise), but in this case, they measured bulges on the ocean's surface that revealed clues about the subtle gravitational tug of structures on the ocean floor.

The result was a map with twice the resolution of the previous version, made in 1997. In the map below, the red dots show locations of earthquakes with magnitude greater than 5.5, "highlight[ing] the present-day location of spreading ridges and transform faults":

(Scripps Institution of Oceanography)

The researchers argued that better understanding the topography of the ocean floor could improve our understanding of ocean circulation patterns that affect the Earth's climate. So there's that. But there are also all those new undiscovered mountains.

Further reading: Check out all of the new ocean floor images and maps over at the Scripps Institution's page.

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