Largest volcano on Earth

At a size equivalent to the state of New Mexico or British Isles, the underwater shield volcano known as Tamu Massif is the largest individual volcano ever documented on Earth, according to new research to be published in the journal Nature Geoscience.
The underwater behemoth is nearly as big as the giant volcanoes on the surface of Mars, making it not only the largest on Earth, but among the largest in the solar system.
Estimated to be 145 million years old, Tamu Massif's summit is located beneath about 6,500 feet of water in the Pacific Ocean, about 1,000 miles off the east coast of Japan. Parts of its base are believed to be in waters almost four miles deep.
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