Mauna Loa

Mauna Loa, adjoining Kīlauea to the west and reached via Mauna Loa Rd. within Hawai‘i Volcanoes National Park, is the world’s most massive volcano. The summit rises about 56,000 feet above its base (located beneath the floor of the Pacific Ocean) and stands 13,677 feet above sea level. This enormous mountain was built by innumerable lava flows. In the last century, Mauna Loa erupted on an average of once every 3.75 years. The summit is reachable on foot; it is a 19-mile one-way hike from the end of Mauna Loa Road and is typically a 2-day ascent.

One of the more voluminous flows in recent history began in 1950. Very liquid lava escaped from a fissure 13 miles long and reached the sea in less than 3 hours, having advanced at a speed of approximately 3.75 miles an hour. This massive eruption amounted to about 600 million cubic yards of lava, enough to pave a four-lane highway 4.5 times around the world.

With the exception of a brief eruption in July 1975, Mauna Loa waited 34 years before generating another major eruption. On March 25, 1984, Mauna Loa began a 22-day eruption that sent lava flows down its northeast flank from a vent at the 9,400-foot level. The two longest flows extended about 16 miles from the vent. This eruption coincided with yet another eruption of Kīlauea, the first time both volcanoes had erupted simultaneously in 65 years.