Kilauea's most recent lava flows reached the sea over the weekend, and they've been beach bumming ever since. Few things are as dramatic as molten rock contending with seawater. We'll be talking about all the neato things that are happening and that we may see if the eruption continues. We're starting with LAZE, which in this case isn't something you do on a hot summer afternoon. It's this:

An enormous LAZE plume marks the Leilani Estates lava's entrance to the ocean on May 20th, 2018. Credit: U.S. Geological Survey 

When blazing hot lava meets seawater, the interaction between them boils the water and produces enormous plume of mist, called LAZE (lava haze). These plumes are, of course, mostly water vapor, but they are so much more than that. They're acidic beasts carrying appreciable amounts of hydrochloric acid, hydrofluoric acid, sulfate anion, carbon dioxide, and nitrogen dioxide, plus traces of volcanic glass and other particles. Even if you could find a safe place near where the lava is pouring into the ocean, you wouldn't want to be hanging out there without industrial-grade protection.

Sounds super scary, right? Well, it's concerning. But don't panic. It, like so many of Kilauea's other dangers, is something you can protect yourself against with a little common sense and caution. And it's really pretty neat.

The Things a Little LAZE is Made Of

Okay, let's start with hydrochloric acid (HCl) since that sounds super scary. I mean, we know this stuff eats rocks, right? It's got to be hell on human lungs, and it is. HCl is the primary factor causing LAZE's acidity. Concentrations can reach 7.1 parts per million (ppm) within about twelve yards of the contact between lava and seawater. That's quite a bit higher than the 5ppm limit set by OSHA.

Compared to HCl, the amount of hydrofluoric acid (HF) is pretty low. That's a good thing, because this stuff can dissolve glass. And what it does to the human body is truly gruesome. The great news is that the concentrations of HF aren't anywhere near exposure limits set by OSHA, so it's not like the cloud is going to melt your eyeballs on contact. However, comma, it does have an additive effect when it's in the presence of this much HCl, so it's not harmless.

The sulfate anion would be pretty darn concerning if it came in the form of sulfuric acid, but folks who have studied the composition of LAZE clouds think it's more likely to be present as a mineral like gypsum, and the concentrations are very low, so it sounds scarier than it really is.

Other gasses like CO2 and NO2, aren't ideal for breathing, but aren't quite as terrifying as the acids.

You're going to hear a lot about glass, because it seems most news articles about the LAZE love to blare about how these clouds are just full of glass particles and fibers. However, we're talking low concentrations for the most part: around 1.3 milligrams per cubic meter. Sometimes, really close to the source, you may see largeish particles settling out. And these are really, really kinda neat: they're called limu'o Pele, and they look like little flakes of basaltic glass seaweed. Some researchers have measured flakes up to 10 centimeters in diameter! They don't usually get far from their point of origin, though, and you're only likely to see glass flakes and fibers settling close to the ocean, where they're born.

So, the upshot: even if you get stuck in a LAZE plume, you're not breathing in clouds of pure acid and glass, here, folks. It's dangerous, but not instantly lethal. And there's even better news!

Concentrations Diminish Drastically with Distance, Yay!

Seriously. They go down by a lot. Let's go back to our fiendish HCl: if you get about a hundred yards from the source of the plume, concentrations are already dipping well below OSHA exposure limits, down to around .69 ppm. And by the time you've gone a few miles from the source, even if you're getting misted by the plume, levels are so low they can't even be quantified. Now, this can vary depending on the size of the plume: larger plumes will probably have greater concentrations and will take longer to dissipate. But if you're a mile or two inland with the wind blowing the LAZE your way, there's no need to panic.

How to Stay Safe from the LAZE

Pay attention to where lava and sea are meeting, and which way the winds are blowing, so you can avoid the high concentrations of HCl and other dangerous LAZE components near their source. If you need to be within the area, proper protective gear, such as a chemical cartridge respirator and either eye goggles or a respirator with a full face shield will help protect you. If you're going to be that close, talk to experts in the area for more tips on how to guard yourself from over-exposure.

If you can get out of the area of the plume, do, especially if you're elderly, have cardiopulmonary or respiratory problems, or are with children. Folks who are sensitive to this stuff may feel ill effects even at low concentrations. If you're in the area where the LAZE is blowing, try to stay inside with doors and windows closed until it passes. And of course follow all emergency alerts and recommendations for your area. There are lots of people out there monitoring where the LAZE is, what's in it, and how bad it is. They'll be sending out regular recommendations.

Now that we're not utterly terrified of it, let's learn some very fascinating facts about LAZE. Namely:

That HCl Doesn't Come from Lava

How wild is that? But it's true. The lava itself isn't pumping out copious volumes of hydrochloric acid when it meets the sea. That stuff's coming from the seawater itself.

"But, Dana!" you cry. "I swim in the ocean all the time, and my skin doesn't usually melt off! What the actual heck?"

A funny thing happens when ultra-hot lava hits the water. That seawater, rich in dissolved salts and minerals, gets vigorously boiled away, hence the gigantic clouds of steam. All that fury breaks down magnesium chloride salts, generating the lion's share of the hydrochloric acid gas found in the plume. And the CO2 comes from hapless little bicarbonate and carbonate ions contained in the boiled brine. There is some intense chemistry going on in there!

Oh, and if you're wondering about the sulfur dioxide that's been dominating the news of volcanic gasses lately: LAZE hasn't got much. By the time the lava reaches the ocean, most of it has already outgassed. There's a very neat illustration of this by Simon Carn here.

So, yes: don't laze about in the LAZE. But definitely do learn more about it! It's another one of those amazing things that happens when Pele decides to add a little more beachfront property to her island.

A hapless house looks on as lava and water meet, generating a vigorous LAZE plume on May 20th, 2018. Credit: U.S. Geological Survey


Edmonds, M. and Gerlach, T.M.: The airborne lava-seawater interaction plume at Kilauea Volcano, Hawai'i.

Kullman et al: Characterization of air contaminants formed by the interaction of lava and sea water.