VOLCANO, Hawaii Island — In the past few days, the Big Island has seen seen more than its share of unusual geologic phenomena.
First: the lava lake in Halemaumau, the inner crater at the summit of the Kilauea volcano, overflowed and covered most of the caldera floor with a fresh coat of glowing lava.
Then the floor of Puu Oo, a frequently active cinder cone downhill from Kilauea, rapidly collapsed. Scientists detected the missing magma moving down Kilauea’s East Rift.
Then it emerged in spectacular lava fountains in the middle of Lower Puna’s Leilani Estates subdivision.
And then there was something that not even longtime Big Island residents had seen: pink clouds at noon. They started with a pink plume out of Puu Oo, but within a few days, roseate clouds were mingling with regular gray and white ones from Puna to Kau.
This image released by the U.S. Geological Survey shows a reddish-brown ash plume at 12:46 p.m. Friday that occurred after a magnitude-6.9 earthquake on the south flank of Kīlauea.
AP
Scientists at the U.S. Geological Survey’s Hawaii Volcano Observatory have been tracking all this. From their headquarters overlooking Kilauea’s summit caldera, they monitor a vast web of instruments spread over the volcano’s surface: tiltmeters, seismometers, GPS tracking systems, instruments measuring gas emissions, all designed to detect even the tiniest change in the volcano’s behavior.
That web even extends into the sky, downloading data from orbiting satellites.
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Once the lava finally emerged, teams of scientists were there to observe and measure those “surficial manifestations,” as lead scientist Jim Kauahikaua called them in a recent interview.
“We have multiple crews on the ground, tracking its behavior, tracking the fissures themselves, tracking the cracks and whether they’re generating any sort of flow,” he said.
At the time, three fissures had already opened up in the subdivision, built in the 1960s right on top of the East Rift: a fault line running from Kilauea’s summit all the way down to the sea, along which lava has traveled to cause eruptions in the past. Since the interview, said Wendy Stovall, more fissures have opened nearby.
Stovall’s currently the deputy scientist in charge at the U.S. Geological Service’s Yellowstone Volcano Observatory in Yellowstone National Park. But for years before that, she worked on Kilauea, so when the current volcanic crisis happened, she volunteered to serve as the USGS spokesperson so that Kauahikaua and the other scientists here could concentrate on their work.
A pinkish plume was visible Thursday afternoon over Kilauea Volcano’s Puu Oo crater.
Jason Armstrong/Civil Beat
Those pink clouds, she said, were formed when lava emptied rapidly out of its reservoir beneath Puu Oo’s floor, causing the walls of the cinder cone to collapse. The lava of the cinder cones, she said, were rich in iron.
“Because the rocks in Puu Oo have been oxidized, they’re really red, she said.
Once that lava started disappearing from Puu Oo’s reservoir, the guessing game began: Where was it going to come out?
One way to track magma you can’t see is through seismometers, which detect the vibrations of earthquakes — even those humans normally don’t notice — such as the ones that lava creates as it moves underground. By comparing the times when the same earthquake reaches different seismometers and then triangulating between them, volcanologists figure out the quake’s point of origin.
Tiltmeters measure the usually tiny changes in the surface rock as the magma beneath causes it to swell or sink. In recent years GPS-based devices have also been employed, along with radar and other satellite instruments.
One of the earliest warning signs of the current activity, for instance, was an interferogram: a map of surface deformation based on overpasses of the European Space Agency’s Sentinel-1A satellite from April 19 to May 1.
A European Space Agency interferogram shows deflation around Halemaumau crater and Puu Oo.
USGS
When the images gathered from those overpasses were superimposed, minute changes in land elevation created a telltale pattern of bands around the Puu Oo region, showing that it was sinking as the magma drained from under it. The same map suggested where it was going: down the East Rift toward Leilani Estates.
Friday’s two big earthquakes, said Stovall, were not just caused by the movement of underground lava. They were tectonic, involving movements of the earth’s crust itself.
Under the volcano, a “decollement fault” marks the boundary between the ancient sea floor and all the volcanic rock that has piled up on top of it, forcing it downward. When enough magma shifts, the change in weight causes the volcanic stone to break loose and slide on this crustal interface, causing a tectonic quake.
Once a major tectonic quake occurs, the crust all along the fault has to readjust, causing more quakes. Big Islanders experienced dozens of subsequent smaller quakes — adding one more wrinkle to the scientists’ job. Which quakes came from the magma itself? Which from the tectonic plate?
The main purpose of all this tracking is public safety. And lava isn’t the only threat to the public during an eruption. One of the deadliest dangers, especially with Kilauea, is gas.
A photo of the Leilani Estates eruption, take from a temporary research camera.
USGS
Kilauea has some of the hottest magma on earth: Liquid basalt comes from the earth’s mantle, blowtorching its way straight through the earth’s crust to the surface. Basaltic magma, which has a temperature of 2,200 degrees Fahrenheit, is mostly silicone. But the lava here also contains sulfur, which has a boiling point of only 832.3 degrees. When basalt hits the surface as a liquid, superheated gaseous sulfur bubbles out, quickly combining with hydrogen and oxygen from water to form two noxious gases, hydrogen sulfide and sulfur dioxide.
One of the reasons that the Hawaii County Civil Defense Agency ordered the mandatory evacuation of Leilani Estates was that the fire department was reporting high levels of sulfur dioxide gas in the air.
But there’s another danger the instruments can’t detect. Scientists didn’t sell residential lots atop the East Rift. Since the lava emerged in Leilani Estates, some people have ignored the “keep out” notices and entered the eruption zone anyway. And scientists have had problems with tracking the flow as it neared the subdivision because, Stovall said, “Unfortunately, some of the seismometers were vandalized.”
Against stupidity, science has not yet found a cure.
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