The United States Geological Survey recently released its “Volcanic Threat Assessment.” That’s an indicator of the potential severity of impacts that could result from future eruptions at various volcanoes. Hawai'i Island’s Kīlauea Volcano was number one on the list – with the greatest potential impact. But that does not mean a new eruption is imminent, even though the volcano erupted continuously from 1983 until early August of this year.
Scientists stress, Kīlauea is not erupting. The lava flow of summer, 2018, which included effusive lava in the Lower East Rift Zone plus frequent collapse and explosive events at the Kīlauea summit, began on May 4th. August second was the last collapse at the summit, and on August 4th, the lava stopped flowing. Hawaiian Volcano Observatory research geophysicist Ingrid Johanson puts the eruption in perspective.
“The events of the summer really reminded us what a complex system Kīlauea Volcano is. Inside the volcano there were a lot of processes happening, Puʻu Ōʻō was starting to inflate with the lava lake rising and overflowing. And when the intrusion started heading towards the lower east rift zone, the system was primed for sending a lot of material downrift.”
Geophysicist Jim Kauahikaua has studied Kīlauea for close to 40 years and says the summer lava eruption was nothing new.
“Kīlauea’s gone through a number of cycles very similar to this over its last couple of centuries, where the lava level will rise significantly in the summit over years and then it will all collapse and sometimes that pushes lava out into the rift zones, sometimes it doesn’t. This is tenth or fifteenth in the last couple hundred years of events like this.”
There were similar eruptions in 1955 and 1960 in the Lower East Rift Zone. Kauahikaua says the 1840 eruption, which ended with lava entering the ocean in Puna, was most similar to this summer’s eruption.
Today, there are small earthquakes at the summit, and Johanson says those will continue. Magma continues to move underground. Kauahikaua says the last visible surface lava downrift was September fourth. The air quality around the island is excellent. Scientists say at the height of the summer’s eruption, more than 50,000 tonnes per day of sulphur dioxide were going into the air. Today it’s less than a thousand tonnes per day.