Rising gradually to more than 4 km above sea level, Mauna Loa is the largest volcano on our planet. Its long submarine flanks descend to the sea floor an additional 5 km, and the sea floor in turn is depressed by Mauna Loa's great mass another 8 km. This makes the volcano's summit about 56,000 ft above its base! The enormous volcano covers half of the Island of Hawai`i and by itself amounts to about 85 percent of all the other Hawaiian Islands combined.
http://www.youtube.com/watch?v=-8cmUcl6UXM&safety_mode=true&persist_safety_mode=1