Throughout Kilauea’s ongoing and spectacularly destructive eruption, our eyes have mostly been trained on the fire fountains and vast river of lava flowing through the lower East Rift Zone. But there’s also been an incredible amount of drama unfolding at the volcano’s summit that shows no signs of letting up.
Not two months ago, the Halemaʻumaʻu summit crater was a fiery lake of lava. But just as fissures started to open in the lower East Rift Zone in early May, that lake began draining downward and receding from view, prompting warnings of an explosive eruption should the magma level fall below the water table. Sure enough, explosive eruptions of gas and ash revved up a few weeks after the collapse began as the crater’s walls crumbled and produced rockfalls.
Nearly seven weeks on from the start of the hullaballoo, the transformation of Halemaʻumaʻu crater has been stark. A drone flyover on June 13 shows that where the lava lake used to be, there’s now a deep, steep walled pit wafting a acrid sulfur dioxide gas and belching the occasional ash plume.
The U.S. Geological Survey (USGS) noted in an update on June 12 that the crater’s deepest section is now about 300 meters (1,000 feet) below the rim, meaning you could stack about two Washington monuments in it before reaching the top. The slumping has continued unabated ever since, with one nearby GPS station subsiding an additional 200 feet over the past week, according to an update the agency posted on Monday.
Satellites are offering additional insight into the nature of the change taking place. Take this animation released by USGS on June 15, which overlays a series of radar images acquired by the Agenzia Spaziale Italiana CosmoSkyMed satellite system. Darker regions indicate deeper terrain, clearly showing the slumping of parts of the western, southwestern, and northern crater rim over time.
A separate visualization made from data collected twice every six days by the European Space Agency’s Sentinel 1 satellite uses colored fringes to indicate deformation. Per USGS, the smearing of those fringes in the center of the caldera bowl is “a sign of the extreme and rapid style of subsidence.”
As dramatic as it seems, this is pretty much what geologists would expect to happen as magma continues to drain and move downrift. The magma pressure at the summit is now much lower than it used to be, and like a water balloon that sprung a leak, it’s slumping and deflating as a result.
“If you look at a lot of these big shield volcanoes, these collapse calderas are fairly common features,” Denison University volcanologist Erik Klemetti told Earther. He added that when Iceland’s Bárðarbunga volcano erupted in 2014-2015, the caldera (which in that case was buried beneath a thick glacier) saw “significant collapse” as eruptions occurred off to the northeast.
There’s still no indication of when any of this will let up. “I think it’s anybody’s guess,” Klemetti said.