Unless you’ve been living under a lava bed, you’ve heard all about the dramatic increase in volcanic activity at Kilauea last month. But one thing that you might not know is that Kilauea has been continuously erupting for the last 35 years. Pu‘u ‘Ō‘ō, a volcanic cone in Kilauea’s Eastern Rift Zone, first began erupting on January 3, 1983 and hasn’t stopped since. On May 3, 2018, a 5.0 earthquake ripped open some new fissures in the Earth near the Leilani Estates area, allowing magma associated with the Pu‘u ‘Ō‘ō eruption to surge through these fissures. The next day, a 6.9 magnitude earthquake – the largest earthquake to hit Hawaii since 1975, created additional fissures and even spawned a minor tsunami that thankfully did not cause any damage.
Kilauea is very different from the volcanoes that dot the Cascade Range. While our volcanoes are formed due to the Juan de Fuca plate subducting, or moving under the North American plate, Kilauea was formed by the “Hawaii Hot Spot.” Hot spots are regions of mantle under the Earth’s surface that are hotter than the surrounding mantle, and when this hotter-than-normal mantle rises and encounters the Earth’s crust, it melts the crust to form magma. This magma then rises to the Earth’s surface as lava to build volcanoes. Hot spots tend to remain stationary over time while the Earth’s plates move over them, and the Hawaiian Islands are a perfect example of this, with the islands becoming older and more heavily eroded the further they move from the hot spot.
Pu‘u ‘Ō‘ō formed in the same manner as many volcanic cones on Hawaii, with magma bursting through a fissure formed along a “rift zone”. Though Kilauea has a summit caldera and an enclosed crater that is currently active, much of the magma from the magma chamber under the summit flows along these rift zones that flank the volcano, either making it to the surface through these fissures or flowing directly into the ocean via lava tubes.
Could the most recent fissures create a prominent cinder cone in the Leilani Estates and mark a shift in volcanic activity from Pu‘u ‘Ō‘ō to the Estates? Such a question is above my pay grade, but such a shift has happened in the past. In July 1986, the structure that supplied magma to Pu‘u ‘Ō‘ō collapsed, cutting off the supply of magma to the cone and shifting the eruption two miles to the northeast. The eruption then returned to Pu‘u ‘Ō‘ō in early 1992. It’s lava lake drained significantly a few days before the current fissures at the Leilani Estates formed, but since the supply of magma to Pu‘u ‘Ō‘ō does not appear to have been disrupted, the volcano itself will likely remain active. However, it is possible that volcanic activity at Pu‘u ‘Ō‘ō will decrease simply because much of its magma supply is now being directed elsewhere.
As of May 19, lava flows from the fissures have devoured over 40 structures in the Leilani Estates subdivision and adjacent areas, and sulfur dioxide and “laze” – acidic and poisonous haze created by lava flowing into the ocean, have made life less than ideal for many on the Big Island. But in the grand scheme of things, Kilauea’s eruptions are very gentle and forgiving compared to the catastrophic eruptions that are common to the stratovolcanoes found in the Cascade Range. For example, the opening salvo to Mt. St. Helens’ 1980 eruption was a 0.7 cubic-mile landslide that rushed down the mountain at speeds of up to 150 mph and created a 600 foot megatsunami in Spirit Lake. The most dramatic thing that has happened with this latest eruptive episode are towering 300-foot lava fountains that temporarily pop up across the region. I don’t know about you, but I’ll take the lava fountains.
Charlie Phillips, a Madrona resident, received his B.S. in atmospheric sciences from the University of Washington and works in Portland as a meteorologist forecasting wind energy along the Columbia River Gorge. Check out his weather website at to charlie.weathertogether.net.