A 1969-1974 eruption of Mauna Ulu put on a spectacular show. This photo was from 1974/NPS files
Mauna Loaʻs last eruption was in 1984 on the Hilo side of the world’s largest active volcano on the planet. No one is predicting that Mauna Loa is about to erupt. But due to what Civil Defense calls an average of 5 years between eruptions. Both Hawaii County Civil Defense (HCCD) and U.S. Geological Survey (USGS) staff in Hawai’i say you should be prepared.
Mauna Loa has erupted 33 times since 1843 averaging once every five years. Over a longer period of time, the past 3,000 years, it’s estimated to have erupted once every six years. We are currently in the volcano’s longest quiet period since written records have been kept, with no eruption since 1984.
Manua Loa is no small volcano. The volcano makes up roughly 51% of Hawaiʻi Island and stands 13,681 feet (4,170 m) above sea level. More impressive, however, it raises an astonishing 30,000 feet (9,144 m) from the bottom of the sea, a greater height than Mount Everest. The ocean floor actually bends under the weight of this mammoth mountain. By itself, the landmass that Mauna Loa encompasses is almost equal twice all of the other Hawaiian islands combined. Eruptions of Mauna Loa have historically been characterized by high volume flows that produce lava capable of traveling long distances, contributing to its shape. Scientists believe that 90% of the volcano’s surface has been covered with flows that erupted within the past 4,000 years.”
Hawaii Volcano Observatory has recently recorded around 175 small-magnitude earthquakes below Mauna Loa in the last week. Rates of deformation and seismicity at the summit remain slightly elevated, however, there is no significant change in patterns that would indicate increased volcanic hazard at this time.
Mauna Loa eruptions tend to produce voluminous, fast-moving lava flows that can impact communities on the east and west sides of the Island of Hawaiʻi. Since the mid-19th century, the city of Hilo in east Hawaiʻi has been threatened by seven Mauna Loa lava flows. Mauna Loa lava flows have reached the south and west coasts of the island eight times: in 1859, 1868, 1887, 1926, 1919, and three times in 1950. according to USGS.
How can you prepare for a Mauna Loa eruption?
“The most important thing you can do is to have a personal response plan—especially if you live in or near the red zone. Nowadays, people pack ‘go’ bags containing essential items in case they have to leave their house under an evacuation order. You may want to include important documents, like your birth certificate, deeds, legal papers, and medications.” USGS said.
