When was the last time that volcano in Hawaii blew its top?

rocky Julian Gregory

Hi Mr. Gregory,

There are a number of ways to answer your question. Kilauea has been in constant eruption since January 3, 1983. The first 3.5 years of the eruption consisted of ~monthly eruptions that lasted 10-24 hours or so, interspaced by repose periods of about a month. These eruptions were of the high fountaining variety, and produced fast-moving 'a'a flows and a big cinder cone called Pu'u 'O'o. The last of these high-fountaining episodes occurred in June of 1986. Since then the eruption has shifted into a different mode, with quiet (but non-stop) effusion of pahoehoe lava in lava tubes. This activity built the Kupaianaha lava shield about 3 km downrift from Pu'u 'O'o between July 1986 and Feb 1992, and another (yet un-named) lava shield against the uprift flank of Pu'u 'O'o. There have been a few breaks in this activity for up to 3 days, but otherwise it has been essentially constant effusion of lava at about 5 cubic meters/second.

Mauna Loa (the other active volcano on Hawai'i) last erupted from March to April of 1984. This eruption produced fast-moving 'a'a flows that reached to within about 10 km of the outskirts of Hilo.

If you mean when did Kilauea last have an explosive eruption (i.e. "blow its top"), then the answer is 1924. At that time the long-lived lava lake within the Halema'uma'u pit crater (within the summit caldera) drained downrift. This apparently allowed groundwater to seep in and contact the hot rocks. No new lava was erupted but the resulting steam explosions blew out lots of the plumbing system within the volcano. If you go to Halema'uma'u today you can see many of these blocks littering the area.

I hope this answers your question. I guess the point is that explosive eruptions are very rare on Hawaiian volcanoes, and require water to somehow be involved.

Sincerely,

Scott Rowland, University of Hawaii 

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