An overflow of Kilauea’s summit lava lake at Halema’uma’u in late-April was followed a few days later by lava drainage-linked crater floor collapse at the volcanic cone Pu’u ‘O’o, an uptick in seismic activity, an ash-rich eruption at Pu’u ‘O’o, and the emergence of lava-effusing fissures in the nearby Leilani Estates.
At the same time, the lava lake at Halema’uma’u has drained to such an extent that there has been some concern that the eruption here could become far more explosive.
As the lava here has now fallen back into the conduit below the water level, steam is being generated. Right now, rock falls are creating pulses of vigorous ash emissions. If a rock fall blocks off the conduit, however, this could cause a huge steam-based pressure build-up, which could trigger a sizeable blast akin to the 1924 paroxysm.
The worry is that this could not only generate a prominent eruption column, whose ash threatens aviation and those on the ground, but it could further destabilize the structural integrity of the country rock here, causing further dangerous blockages.
As it happens, over the last few days, explosive activity at Halema’uma’u has intensified. As of Tuesday, May 15, ash from Halema’uma’u’s Overlook vent has risen to as high as 3,660 meters (around 12,000 feet). Volcanic air pollution, or “vog”, is drifting over nearby Pahala.
This ash generation is down to these rock falls and the explosive mingling of water and magma down in the conduit. Whether it be through a full blockage or just more rock falls and water-magma interactions, there’s a chance that the activity here will intensify somewhat.
That’s why the alert was issued – out of an abundance of conservative, well-reasoned caution, for those in the air and on the ground. Don’t believe the hype: as Krippner stressed (in all caps, originally), this will be “nothing like Mount St. Helens or Krakatau!”