Small explosions rocked the summit of Hawaii’s Kilauea volcano on Wednesday while blue flames rippled and lava continued to spew from nearly two dozen fissures in the ongoing eruption on the Big Island that’s showing no signs of slowing down.

Kilauea has been erupting continuously at low levels since 1983. But activity ramped up dramatically three weeks ago, triggering the largest earthquake Hawaii has felt in nearly 40 years and opening up a total of 22 fissures spewing red-hot lava. Though the lava has only oozed and spattered onto a small area of the island, at least 44 structures have been damaged, thousands of residents are affected by toxic air from the volcano’s sulfur dioxide emissions, and one person has been injured so far by a “lava bomb.”

Last week, the Big Island’s youngest and rowdiest volcano shot out “dense ballistic blocks” up to 2 feet across, quaked at its summit, and released several ash clouds, according to the US Geological Survey. The ash billowed so high that the Hawaii Volcano Observatory issued a red alert for aircraft to avoid the area for fear of damage to engines.

“At any time, activity may again become more explosive, increasing the intensity of ash production and producing ballistic projectiles very near the vent,” USGS said Wednesday. The agency is also warning about the health risks of “laze,” or plumes that form when lava hits the ocean.

“The interaction sends hydrochloric acid and steam with fine glass particles into the air,” USGS said. “Laze drifts with the wind and can be a health hazard for people downwind. Laze is irritating to the lungs, eyes and skin.”

Scientists are also watching the eruption from farther away to get some insight into how the ash and sulfur dioxide emissions are affecting the area around it. Using satellites, NASA has tracked how the eruption has played out so far.

Latest view of the #Kilauea hot spot fissures in eastern #Hawaii - seen from the #SuomiNPP satellite this morning. Notice the low-level steam cloud (in yellow) blowing from the site of the eruptions. pic.twitter.com/GfTpO76MOs — NOAA Satellites (@NOAASatellites) May 21, 2018

In particular, NASA is paying close attention to the sulfur dioxide emanating from the volcano.

High in the stratosphere, sulfur dioxide reacts with moisture to create sulfuric acid, creating an aerosol that reflects sunlight back into space. A massive volcanic eruption, like the 1991 eruption of Mount Pinatubo in the Philippines, can inject enough sulfur dioxide into the atmosphere to measurably cool the whole planet.

So far, we’re definitely seeing a major uptick in sulfur dioxide emissions, but we aren’t seeing planet-changing amounts of the stuff from the current Kilauea eruption.

Health officials on the Big Island have issued a sulfur dioxide advisory as winds spread the gas, though air quality remains good on most of the island so far. But officials caution that the eruption could become more explosive at any time, as lava levels have fallen at one of Kilauea’s craters, and there are still potential health hazards from vog — volcanic fog formed when erupted gases react with moisture in the air — and the laze. Air currents can then smear vog and other toxic gases over a wide area, as you can see in this simulation of wind and sulfur dioxide across Hawaii:

There also remains the possibility that the current eruption will get worse. “Due to the current activity, residents down rift should be prepared to voluntarily evacuate at a moment’s notice,” the Hawaii County Civil Defense Agency said Thursday.

For more on the Kilauea eruption and other historic volcanic events, listen to the May 16 episode of Today, Explained.