Kilauea, continuing to showcase its eruptive wares to the watching world, isn’t just content with producing blue fire. As reported by the United States Geological Survey (USGS), it’s also creating its own damn weather systems. Specifically, it’s producing “pyrocumulus” clouds, the volcanic equivalent to cumulus clouds – which can cause thunderstorms.
Sometimes known as flammagenitus clouds or simply “fire clouds”, these are formed when intense heating of the ground triggers the formation of large convection cells, where warm air rises, normally imbuing itself with moisture as it goes. When it reaches a point of stability in the atmosphere – when the air mass is as dense as the air surrounding it – it stops moving.
The cooler air around it then condenses out, and these impressive clouds form. Any meteorology fans out there may have clocked that this is essentially what you need to fuel a thunderstorm: moisture, a buoyant lifting force (the heated surface), and a mass of unstable air.
The USGS explains that they pose the same hazards as a thunderstorm. “They don’t hold volcanic ash, so they don’t have any additional hazard from electrostatically charged ash particles.” Indeed, they’re not to be confused with ash columns erupting from (normally) explosive eruptions, which can, under certain conditions, create volcanic lightning and thunder – the latter of which was just recently recorded for the very first time.
Funnily enough, pyrocumulus cloud formation isn’t normally associated with this type of volcanic eruption. It's normally associated with paroxysmal, explosive volcanic eruptions or enormous forest fires.
Back in 2014, for example, California was experiencing a somewhat exceptional drought. Vegetation became far drier than normal, and in August of that year, huge forest fires were ignited, with more than 400 square kilometers (150 square miles) turned into a conflagration in a matter of a few days. This intense supply of heat, as it so happens, created pyrocumulus clouds that could be seen from space.
In the case of Kilauea, however, it appears that the hardworking Fissure 8 – one of the most active, by far, in the lower East Rift Zone (LERZ) – is seemingly supplying so much thermal energy to the ground there that it’s enough to cause a giant mass of warm air to elevate.
Pyrocumulus clouds aren’t particularly threatening – no more than normal thunderstorms, anyway. Just one of plenty of types of volcanic weather, you’re more likely to be threatened by volcanic fog, or vog. This mixture of carbon dioxide, water vapor, and sulfur dioxide – which readily reacts with water to form sulfuric acid droplets – tracks with how much sulfur dioxide is emerging from the fissures.
Unfortunately, since the geochemical change in Kilauea’s magma in the recent past, the Hawaiian Volcano Observatory has tracked a significant uptick in the effusion rate of sulfur dioxide. Although not immediately threatening, it can be hazardous if you’re overexposed to it, or if you have a pre-existing respiratory problem.
“Volcanic gas emissions remain very high from the fissure eruptions,” the latest USGS advisory notes. “If a forecast shift in wind direction occurs today, widespread vog could occur on the Island of Hawaii.” As ever, follow the advice of the authorities, and if possible, don’t breathe it in.
Sure, volcanic weather – like vog, and the acidic plumes of laze on the coast – serve as a reminder that the ongoing eruption at Kilauea is potentially dangerous. The risks don't change the fact that, on a purely aesthetic level, you just have to give Kilauea some respect: From lava fountains reaching heights of a 15-story building to creating its own goddam weather, what more could you ask for at this point?
Curious, I asked the USGS if there's any other type of volcanic weather out there.
“We're not sure...but we do know that volcanic eruptions can occasionally blow holes in existing weather,” they explained. “Back in the 1980s, when Pu’u ‘O’o would experience high fountains, it would stop raining in the vicinity of the fountain, and then start raining again when the fountain ceased.”
That's not all: as pointed out by volcanologist Dr Janine Krippner, you can also get lava-powered waterspouts.
