active volcano in the southwestern Pacific Ocean, within the French overseas country of New Caledonia, although France's claim is disputed by Vanuatu. Matthew Island is located some 320 miles (500 km) east of the New Caledonian mainland. It was sighted in 1788 by the English mariner Thomas Gilbert and was named for one of his close associates. Because of the volcano's continuing eruption and the opposing forces of erosion, the island varies in size and height. It is uninhabited.