Similar water-driven explosions took place during the 1924 explosive eruption at Kilauea, and back then, boulder-sized volcaniclastic blocks were blasted out of the summit, which resulted in at least one fatality.
It’s thought that much the same is happening now. Wednesday’s update by the USGS' Hawaiian Volcano Observatory (HVO) provided the most recent detailed information about the ongoing events at Kilauea and the East Rift Zone. Peppered with plenty of noteworthy remarks, the one that got everyone’s attention is this:
“This morning dense ballistic blocks up to 60 cm (2 feet) across were found in the parking lot a few hundred yards from Halema’uma’u,” which means some significant explosive activity down there in the throat of the volcano is ejecting some microwave-sized ballistics skyward.
As the USGS noted in that same advisory, with regards to the fresh ballistics: “These reflect the most energetic explosions yet observed and could reflect the onset of steam-driven explosive activity,” adding that “further observations are necessary to assess this interpretation.”
The advisory adds that “additional such explosions are expected and could be more powerful,” and indeed that appears to be the case with the latest blast.
With this particular event, the ash fallout is likely to be the dominant threat here. Although only rarely deadly, it can cause problems to those with pre-existing respiratory ailments. Do your best to avoid it as it settles from the sky.
Details remain sparse, but don’t panic: This is, once again, a relative uptick in the explosivity at Kilauea. Don’t believe any nonsense about a Krakatoa-style explosion you may have seen elsewhere online. (A splendid rundown of the misinformation that’s gone around can be found here.)
Regardless of what happens next, the USGS, as ever, is just being cautious as they continually monitor the situation. You’ll be fine as long as you pay attention to what the HVO are saying and you don’t act recklessly.