Mauna Loa is the world's largest volcano and is located on the Big Island of Hawaii. While considered dormant, the volcano has erupted 33 times since its first recorded eruption in 1843, according to the U.S. Geological Survey, with the last eruption occurring in 1984.
Mauna Loa, which means "long mountain" in Hawaiian, is a sheath volcano that extends from depths of 3,100 feet below sea level to a maximum height of 13,697 feet above sea level. Its caldera is 1.9 miles wide and 3.7 miles long. The weight of Mauna Loa is so great that it causes the Pacific plate, on which it sits, to sag. According to West Hawaii Today, scientific evidence suggests the mountain has erupted an average of once every six years over the past 3,000 years. Even though it has been several decades since the last eruption of Mauna Loa, the USGS continually monitors the volcano for signs of an impending eruption using seismic measuring devices. These devices detect earthquakes or explosions deep within the earth that signal a potential eruption. While the oldest rocks found on Mauna Loa date to 100,000 to 200,000 years ago, most of the material that forms the surface is relatively young. Scientists estimate that 98 percent of the surface is covered with materials less than 10,000 years old.