The Answer:

Hawaii's Mauna Loa is not only the largest active volcano in the country, but the largest in the world.

Rising 13,680 feet into the sky, Mauna Loa's appearance above sea level is only a part of the story. Below the surface, Mauna Loa is a marine giant, depressing the sea floor an additional 26,000 feet and measuring about 56,000 feet from its base to summit.

In addition to being the world's biggest, it is also one of the world's most active. Its most recent eruption was in 1984.

To learn more about Mauna Loa, visit the Hawaiian Volcano Observatory or check out our Volcanoes of the World section.

—The Editors