Kilauea eruption changes much: landscape, park operation, science's understanding
KILAUEA, Hawaii - Forty nine days ago, the volcano started its latest eruption, and the national park around it closed for visitors' safety. Thursday, for the first time since that closure,Hawaii Volcanoes National Park invited media in to look at how much the landscape has changed.
One obvious change: the Kilauea caldera is quickly getting bigger. USGS research geophysicist Kyle Anderson says, "The summit magma reservoir is deflating. Think of it like air being let out of a balloon. That's causing subsidence, deformation, and fracking across a broad and widening region of Kilauea Caldera."
As the crater walls and inner caldera slump inward, the depth of Halemaumau has more than tripled and the diameter has more than doubled. The bottom is now almost 440 yards lower than the old caldera floor.
Anderson says some parts of the crater floor drop more than 30 feet a day. During early eruptions, the changes sent plumes of ash tens of thousands of feet into air (an event on May 17, 2018 sent an ash plume to 30,000 feet) and volcanic fragments exploding.
Scientists now see it causing strong earthquakes, but aren't sure why. "It is possible that another partial collapse of the shallow magma reservoir occurred, also changing subsurface geometry. This changed the character of the seismic waves, which now have more high frequencies (shorter wavelengths) that people may feel more intensely. An analogy is a home theater or car stereo. Imagine you have it set at a constant volume (like the consistent earthquake magnitude) but then change the dials to increase the treble while lowering the bass slightly. The total energy is the same, but it's just being expressed in different frequencies," the USGS says.
Park staff point out a series of cracks in the parking lot and in wall at Jaggar Museum. According to USGS, before May, about ten earthquakes per day were typical at the summit. As of late June 2018, there are about 600 earthquakes located in the same region on a daily basis.
"What is causing these earthquakes? The short answer is that the rigid rock of the caldera floor is responding to the steady withdrawal of magma from a shallow reservoir beneath the summit. As magma drains into the East Rift Zone (traveling about 26 miles underground to erupt from fissures in the Leilani Estates subdivision), it slowly pulls away support of the rock above it. Small earthquakes occur as the crater floor sags. The collapse/explosion event is triggered when the caldera floor can no longer support its own weight and drops downward. Large collapses can produce an explosion and ash plume that rises above the crater," explains the USGS.
They say these quakes are the main reason they're keeping park closed. Park ranger John Broward gives an example of what they're worried about: "If we had visitors in a building and the rift collapses and the floor cracks, somebody gets hurt that way."
They are citing about two people a day for being in the park when they shouldn't. Again, park rangers ask people to stay out for their own safety.
Broward said Thursday, The Hawaii Volcanoes National Park will stay closed indefinitely near Kilauea summit.
Meanwhile, scientists say this eruption has changed some key understandings of the volcano. For instance, Anderson shares, they used to think water caused the explosions, but "now we think water was secondary to those processes if at all. The explosions are driven more by magmatic acids, a real change in our understanding."
USGS scientist in charge Tina Neal says this is a bittersweet event for her to watch as a person, but as a professional, "This is a once-in-a-career phenomenon. We have so much to learn that will help future generations and other volcanology groups around the world."
If you feel strong shaking, remember to drop, cover, and hold on until it stops. Be sure to quake-proof your home, school, and business.