Huge extinct volcano discovered underneath the Pacific Ocean

Scientists at the University of New Hampshire (UNH) have found a gigantic 100 million-year-old ancient extinct volcano at a depth of 4 km underwater in one of the minimum explored areas of the Pacific Ocean. It was discovered on a seafloor mapping mission, aimed at helping delineate the outer limits of the US continental shelf, near the Johnson Atoll in the Pacific. The peak of the seamount emerges 1,100 meters from the 5,100-metre-deep ocean floor.
Mr. Gardner and his team used multi-beam echo-sounder technology to create detailed images of the seafloor. The team was able to map the conical seamount in its entirety. As only low-resolution satellite data exists for most of the Earth’s seafloor, several sea-mounts of this size are not determined in the satellite data but advanced multi-beam echo-sounder missions like this one can determine their existence.
A seamount is usually made from extinct volcanoes that rise suddenly and are generally found rising from the seafloor.