Mauna Loa—World’s Largest Active Volcano—Erupts On Hawaii

Topline

Mauna Loa, the world’s largest active volcano, started erupting for the first time in nearly 40 years late Sunday night, spreading a lava stream down Hawaii’s Big Island and spreading ash and toxic gasses, as residents are advised to remain “vigilant.”

Key Facts

The Hawaii Department of Health advised residents on the Big Island to prepare for poor air quality from ash, sulfur dioxide and vog (a noxious mixture of sulfur dioxide, oxygen and moisture), warning that “conditions are changing rapidly” and poor conditions can be “very localized.”

Although the lava flow is not expected to affect any communities on the Big Island, residents are being asked to cut outdoor activities that “cause heavy breathing,” especially among children, seniors and people with pre-existing respiratory conditions.

Hawaii officials closed the Mauna Loa Forest Reserve and the neighboring Kipuka ‘Ainahou Nene Sanctuary for at least 90 days, according to the Division of Forestry and Wildlife, while authorities set up roadblocks in the area of the volcano’s lava flow.

Big Number

51%. That’s roughly how much of the Big Island’s landmass is made up byMauna Loa . The lava flow from the volcano has been centered on the island’s northeastern slope, avoiding the more populous areas of Hilo and Kona to the east and west, respectively. Hawaii County Civil Defense Administrator Talmadge Magno had warned last month that it would be hard to determine which part of the island would be affected by an eruption.

Key Background

The eruption comes just over a month after Hawaiian officials issued a warning an eruption could be coming, following a significant uptick in earthquakes around the volcano. Over the course of a month, the number of earthquakes rose from between 10 and 20 per day to around 40 to 50 per day, including a 5.0 magnitude earthquake—sending the volcano into a state of “heightened unrest,” according to the Hawaiian Volcano Observatory. There were no deaths reported when Mauna Loa last erupted in 1984, although the lava flow came dangerously close to the city of Hilo, the largest community on Hawaii’s big island. The 38-year dormant period since that eruption was the longest period of inactivity in recorded history, according to the U.S. Geological Survey. The last major eruption on Hawaii came in 2018, when the Kilauea volcano spewed lava, destroying 700 homes.

Further Reading

Hawaii Officials Warn World’s Largest Active Volcano Could Erupt (Forbes)

Mauna Loa eruption causes flight delays, some cancellations (Hawaii News Now)

No danger yet as Mauna Loa lava flows on the Big Island (Honolulu Star Advertiser)