Scientists have analyzed tiny quartz crystals to determine the amount of lead time humanity might have before an enormous volcanic eruption, and their conclusion is that there may only be one year of warning.

The researchers focused on the kinds of giant volcanic eruptions that haven’t happened for a very, very long time, like a super eruption in New Zealand that occurred 26,500 years ago. First, a huge amount of magma has to build up, which can persist for hundreds or even thousands of years. Then, it needs to erupt. And, according to a new study, it might just take a year for the actual eruption process— that transition from build-up to eruption— to happen.

“[W]e have shown that the onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption,” Guilherme Gualda, an associate professor at Vanderbilt University and first author of the new study, said in a statement.

Gualda and another scientist used quartz crystals from the site of a super volcanic eruption in California that occurred 760,000 years ago, analyzing them to determine how long it took rims on the crystals to grow, a factor that is indicative of the lead time before a super volcanic eruption. They determined that over 70 percent of the rim growth times were shorter than one year, according to the study, which was published in the journal PLOS ONE.

California isn’t the only place that’s seen a super eruption in this part of the world— in the past two million years, Yellowstone National Park has been the site of three super eruptions. Other spots around the globe that have had super eruptions are found in New Zealand, Italy and Indonesia.

“As far as we can determine, none of these places currently house the type of melt-rich, giant magma body needed to produce a super-eruption,” Gualda said in the statement. “However, they are places where super-eruptions have happened in the past so are more likely to happen in the future.”

The statement announcing their findings refers to the kind of eruption event they studied as “potentially civilization-ending.”