Although still engaging in some curious volcanological behavior, Kilauea’s not making international headlines anymore, partly because its eruption has somewhat settled into a consistent pattern.
Scratch that: Yesterday, a lava bomb – reportedly the size of a basketball, and one of several – careened into a tour boat visiting one of the lava ocean entry points yesterday, injuring a number of people.
Genuinely terrifying video footage shows passengers watching freshly erupted lava mingle with the Pacific Ocean, shortly before a hazy explosion sends ballistics flying their way. Screams can be heard as some of it, including the aforementioned bomb, smash down through the roof.
It seems that 23 have been hurt as a result. According to Mileka Lincoln of Hawaii News Now, 13 of them were sent to the Hilo Medical Center; 12 have been treated and released for burns and abrasions, and 1 has been airlifted to a nearby hospital with a “serious pelvic/leg” wound.
It’s worth noting that such tours normally have a great safety record, and tour companies have just said that this incident hasn't affected their numbers. Clearly, though, accidents can happen when things are more unpredictable.
All things considered, it’s incredibly lucky that everyone on the boat survived. In fact, it’s another testament to the scientists and authorities on the ground there that this has been the first recorded injury of the eruption since a man broke his leg in much the same manner – but on land – back in May.
If anything, this is all a potent reminder that although a largely effusive eruption, it is absolutely a threat to life and property. At the time of writing, 706 structures – mostly homes – have been destroyed, and now 24 people have been injured in total.
So – what happened, exactly?
Volcanic bombs sound fairly dramatic, and to be fair, they often are.
Ejected explosively from surficial volcanic activity, these rapidly cooling, partly-molten blobs of highly dense lava range from several centimeters to just over a meter in size, give or take. As they fly through the air, their plasticity allows them to form strange shapes, which means they aren’t always spherical.
Either way, these super hot, heavy blobs move at incredible speeds. If one lands on you, it’ll crush whatever it hits as well as scorch it. They will, without a doubt, cause serious injury to anything living.
Volcanic bombs are often created when explosive activity – or effusive but energetic lava fountaining – flings fresh lava out of a vent or fissure, but in this case, it was created as lava continued to pour into the ocean offshore from Kapoho Bay. It appears to have flown out of a cloud of laze, a glassy and acidic hazard you can learn more about here.
Lava/magma and water/ice interactions are, well, really complicated. There’s a lot we don’t know about them, and simply adding one to the other doesn’t guarantee anything paroxysmal.
Often, there’s some steam forming as the coolant boils off, and the lava solidifies – that’s it.
Plenty of hydrothermal explosions seem to occur when there’s a certain type of mixing of a certain ratio of water to hot rock/lava. In some instances, you just need to plunge plenty of encased lava into the sea very quickly, like when a solidifying lava delta suddenly collapses.
In this case, it appears the seawater vaporized incredibly violently as it met the lava. This created a sizeable "littoral" explosion, one that sent volcanic debris flying into the air and toward the boat.