Mauna Loa, one of the world's most active volcanoes, is also the world's largest volcano, encompassing almost 2,000 square miles of the island of Hawaii, or about half of the island's land area, according to the U.S. Geological Service. Mauna Loa has erupted 33 times since its first documented eruption in 1843, and its volcanic activity has caused widespread damage over the years, including the loss of human lives and destruction of property.
Damage from Lava Flows
The greatest hazard from the volcano of Mauna Loa is lava flows from eruptions. Early eyewitness accounts of Mauna Loa's active period during the mid-to-late 1800s describe some of the damage wreaked by Mauna Loa's lava flows. A firsthand account of Mauna Loa's 1868 eruption describes an "immense stream of lava" erupting from a crater and moving toward the ocean at a speed 20 miles per hour, destroying everything in its wake, including horses, cattle and land as the local villagers ran for their lives. Another major eruption occurred less than a hundred years later. On the night of June 1, 1950, lava flows from Mauna Loa entered the village of Ho`okena-mauka village in South Kona, cutting through Highway 11, the town's only escape route, and consuming several houses and a post office before traveling out to sea. Fortunately, no lives were taken by lava flows from the 1950 eruption. Most recently, Mauna Loa erupted in 1984, but lava flows caused no significant damage except for burying about 16 miles of land owned by the state, according to the USGS.
Damage from Earthquakes
Mauna Loa has also caused earthquake damage. The USGS explains, "As magma enters and inflates Mauna Loa, the volcano becomes unstable, setting the stage for large earthquakes." These earthquakes can also trigger landslides and tsunamis. An erupting Mauna Loa triggered a massive earthquake on April 2, 1868, with an estimated magnitude of 8.0, causing a landslide and a tidal wave that took many lives and destroyed property. One account of the 1868 quake describes an avalanche instantly burying "ten houses, 31 souls and 500 head of cattle." At the same time, according to the account, "the sea rose 20 feet along the southern shore of the island . . . 108 houses were destroyed and 46 people drowned, making a loss of 118 houses and 77 lives in that district, during this one hour." Mauna Loa's volcanic interactions with sister volcano Kilauea triggered another major earthquake in 1973, resulting in financial losses estimated at $7 million, though no lives were lost.
Damage from Volcanic Air Pollution
Volcanic smog related to Mauna Loa's volcanic activity has negatively impacted human health, destroyed crops and contaminated drinking water. Active volcanoes like Mauna Loa can create volcanic smog, abbreviated as "vog," which forms when volcanic gases such as sulfur dioxide combine with elements in the atmosphere such as moisture and oxygen. Vog can cause respiratory problems for people living downwind of the volcano, kill crops and reduce air and road traffic visibility. It also results in acid rain, which has negative effects on the environment. Even though Mauna Loa itself has not erupted since 1984, it is an active volcano and has indirectly caused volcanic air pollution since its last major eruption. Most recently, in the early 2000s, Mauna Loa began inflating, and soon after, neighbor Kilauea, with whom it shares a complex volcanic relationship, began erupting and creating vog.