It’s fair to say that, when it comes to Kilauea, most of us have been gawping at the lava flows that are currently emerging out of fissures 8, 16, and 18. We shouldn’t forget, though, that there are two distinct acts to this theatrical, incandescent drama.
Shortly after the authorities issued a RED/WARNING alert – more on that here – Halema’uma’u crater at Kilauea’s summit was rocked by a significant explosion on May 17. Ever since, there has been intermittent explosive activity, and new drone footage and photographs by the United States Geological Survey (USGS) has revealed dramatic changes up there.
Only a few months back, this crater was a moderate-sized, lava-filled marvel. Now it’s starting to transform the area into a corroded realm.
The lateral and vertical expansion of the summit crater is breathtaking; it’s swallowing up the ground around it, like a hungry hellish monster. Circumferential cracks radiating from the expanding crater have cut through an old visitor center, and the widening maw has begun to digest part of a parking lot up there.
Rather wonderfully, cloud cover permitting, the USGS has been using overflights to map the ever-changing crater. They're now starting to release a few 3D models of it, like this one:
As noted by the USGS, “the deepest part of Halema‘uma‘u is now about 300 meters (1,000 feet) below the crater rim,” with much of this happening in the last two weeks alone. That's the same depth as 3.2 Statues of Liberty, by the way.
So what’s going on here? Well, it’s down to events that began weeks back.
The lava lake there began to drain quite suddenly as the underlying magma reservoir began dumping its contents out of fissures on Kilauea’s flanks, in the Lower East Rift Zone (LERZ). This led to all kinds of shenanigans, but two proved to be the most important in this regard.
Removing the magma within the volcano weakened its structural support, and rocks began falling into it. At the same time, the magma drained below the water table, which meant that plenty of steam was being generated.
It’s very likely that rockfalls were choking the conduit, leading to the accumulation of trapped steam and, ultimately, explosive activity. “The decompression of the magma reservoir also appears to be resulting in some small explosions, which are really just rapid exsolutions of volcanic gases from the remaining magma,” Dr Michael Poland, the Scientist-in-Charge at the Yellowstone Volcano Observatory (who’s on site to help out), told IFLScience.
This has continued for some time now, contributing to the collapse of the crater walls. "Fundamentally, [though], it's the drainage of magma that's causing all of the activity," Poland explained.
Its caches of molten madness are increasingly empty, so there’s increasingly little left to hold the geology above it up. “The magma pressure at the summit is very low – this is why the summit is deflating and slumping,” the USGS noted on its Facebook page.
Poland explains that, based on current deformation patterns, the progressive slumping won’t be likely to expand to the entire bowl (caldera) in the area, within which Halema‘uma‘u sits. "Instead, it will be focused on Halema'uma'u, and possibly its east side now that the west and north sides have slumped significantly."
Don’t worry, then – no one’s going to suddenly be snatched away by Halema‘uma‘u's collapse.
It’s almost a shame that the rather resplendent lava lake at the Halema‘uma‘u crater has disappeared. The USGS noted that it’s “definitely done, at least for now.”
They added that it might come back, but this will require the LERZ eruption to stop and the summit to re-inflate with a fresh injection of magma.
As incredible as these topographic changes are, I still can’t resist plugging Fissure 8, whose hyperactivity has been both destructive and breathtaking. Not only has its profusions led to the creation of a new delta along Kapoho Bay, but the lava fountaining and spatter here – which is erupting 114-200 refrigerators’ worth of lava per second, by the way – has built up a cinder cone around the fissure that’s about the same height as 10 giraffes stacked atop each other.
