Massive extinct volcano discovered beneath Pacific Ocean

A massive 100 million-year-old ancient extinct volcano has been discovered lurking four kilometres underwater in one of the least explored areas of the Pacific Ocean.
Scientists, at the University of New Hampshire (UNH), on a seafloor mapping mission found a new seamount near the Johnson Atoll in the Pacific.
The summit of the seamount rises 1,100 meters from the 5,100-metre-deep ocean floor.
The seamount was discovered in August when James Gardner, research professor in the UNH-NOAA Centre for Coastal and Ocean Mapping/Joint Hydrographic Centre, was leading a mapping mission aimed at helping delineate the outer limits of the US continental shelf.

Gardner and his team were using multi-beam echo-sounder technology to create detailed images of the seafloor when, late at night, the seamount appeared "out of the blue."
The team was able to map the conical seamount in its entirety.

The yet-unnamed sea-mount, located about 300 kilometres southeast of the uninhabited Jarvis Island, lies in one of the least explored areas of the central Pacific Ocean. Because of that, Gardner was not particularly surprised by the discovery.
"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," he said.

Since only low-resolution satellite data exists for most of the Earth's seafloor, many sea-mounts of this size are not resolved in the satellite data but advanced multi-beam echo-sounder missions like this one can resolve them.
"Satellites just can't see these features and we can," Gardner added.
The seamount's impact remains unknown - for now. It's too deep (its summit lies nearly 4,000 meters beneath the surface of the ocean) to be a navigation hazard or to provide rich fisheries.
"It's probably 100 million years old and it might have something in it we may be interested in 100 years from now," said Gardner.

A seamount is typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor.