You’d think that, in the 19 days since Hawaii’s Kilauea Volcano started erupting intensely, it would have chilled out by now. But nature is relentless: After cracking open 23 fissures, emitting ear-piercing screams, and shooting a guy in the leg with a lava rock, the volcano is now pouring lava into the sea, which, through remorseless physical chemistry, is sending up tiny shards of glass into the air.

In a civil defense alert released by the County of Hawaii on Monday, officials warned that the volcano’s red-hot lava was now rushing into the ocean, creating thick mists of lava haze, or “laze.” They first warned of laze on Saturday, explaining that it’s created “when hot lava hits the ocean sending hydrochloric acid and steam with fine glass particles into the air.” Now, it’s fissure 22 that’s gushing forth the most lava into the sea, so residents there are most in danger of the toxic plumes that are created as the 2,140 °F (1,170 °C) liquid literally boils the sea.

hawaii kilauea fissure 22 laze
Lava from fissure 22, shown here, is estimated to have reached heights of 164 feet before tumbling into the ocean, where it produced laze.

Acidic Steam

It’s possible, according to the United States Geological Survey, for so much hot lava to get into the sea that “the supplied heat is enough to boil the seawater completely dry.” Since boiling creates steam, and both lava and the ocean contain stuff that’s far more potent than just pure H2O, the steam that rises off the boiling water can be extremely dangerous.

The chemicals that are most dangerous are calcium carbonate (chalk), calcium sulfate (gypsum), sodium chloride (table salt), and magnesium salts, which are formed in that order as water evaporation reaches 100 percent. None of these chemicals are particularly harmful on their own, but under extreme conditions, they react with each other in a way that has dangerous effects.

laze chemistry
These are the chemical reactions that lead to the most dangerous parts of laze.

Most important to the creation of laze, the USGS writes, is the creation of magnesium salts. These “react with steam to form hydrogen chloride gas.” When that gas mixes with water, it forms hydrochloric acid, which, true to its name, is acidic, and very strongly so. Breathing in hydrochloric acid can, according to the Centers for Disease Control and Prevention, cause coughing, burning lungs, labored breathing, shortness of breath, and sore throat; at super high concentrations, it can cause pneumonitis, lung edema, and even chronic bronchitis.

laze kilauea volcano
Those clouds may be pretty from afar, but they contain hydrochloric acid and tiny shards of glass.

Shards of Glass

As if acid clouds weren’t bad enough, the steam also carries tiny shards of volcanic glass that are created as lava rapidly cools. In addition to volcanic gases and crystals, magma is partially made up of molten glass, comprising the elements silicon, oxygen, aluminum, iron, magnesium, calcium, sodium, potassium, phosphorus, and titanium.

Volcanic glass is an unusual state of matter that’s formed when magma is rapidly cooled. Slower cooling would allow crystallization — a very orderly organization of the molecules in magma — to occur, but the rush of hot magma into the sea doesn’t allow time for that to happen. The liquid, as Oregon State University volcanologists put it, “‘freezes’ to form volcanic glass.”

The violent movement of the water can break this glass into tiny shards. Those shards can become sediment and stay in the water, as shown in the photo below. However, they become especially threatening when they’re broken up into such fine particles that they’re carried into the air with the rising acidic steam. Rather than try gas masks or respirators, residents near the plumes — which also contain toxic sulfur dioxide, by the way — are simply being advised to stay away.

glass shards sediments kilauea hawaii
Glass shards created by rapidly cooled magma was deposited as sediment when Kilauea spewed lava in 2006.