Federal officials raised the alert level Tuesday for the world’s largest active volcano, Hawaii’s Mauna Loa, which last erupted in 1984.
The U.S. Geological Survey changed the level from “normal” to “advisory” following a steady increase in earthquakes and ground swelling that began in March.
An eruption is not imminent, but scientists are closely monitoring Mauna Loa because of its reputation for “evolving very quickly” and sending lava far and wide, USGS research geophysicist Ingrid Johanson told The Associated Press in a phone interview last month.
“Lava can go from the rift down to the ocean on the west side of Mauna Loa on the order of a couple hours,” Johanson said. “The rate of the eruption is just really fast.”
Mauna Loa has erupted 33 times since 1843.
Its lava flows have stretched to the south and west coasts eight times and neared Hilo, on the east side, seven times. During its last eruption, lava flows came within 4.5 miles (7.2 kilometers) of Hilo, the Big Island’s largest city.
The alert level on Mauna Loa was last raised to advisory in 2015. A similar period of increased activity occurred around 2004, but the USGS Volcano Alert Level system was not yet in place at that time.