The scientists made a 10-hour round-trip trek to and from the test site seven times over seven months. There they collected samples of rock, dissolved gas and microbes, overcoming equipment malfunctions, logistical difficulties, and more along the way. The group was lucky enough to be taking measurements at just the right time—and in the ideal location—to perfectly catch the rise and fall of a rare “swarm” of 2,182 earthquakes. Yellowstone endures a lot of earthquakes, but swarms this powerful tend to occur every five to 10 years, says Montana State University geomicrobiologist Eric Boyd, the study’s lead author.