On May 1, 2018, visitors at Hawai‘i Volcanoes National Park witnessed a startling event: The fiery lake of lava at Kīlauea volcano’s summit suddenly began to drain. Over the following weeks, the lake emptied and the surrounding caldera collapsed—dropping 1,200 feet. More than seven hundred earthquakes rattled the region. New lava vents opened in residential areas within the East Rift Zone, burning hundreds of homes and radically reshaping the coastline.

A year after this dramatic eruption, helicopter pilots spotted yet another surprise inside the caldera—a pool of pale green water. “This is something we haven’t seen in Western recorded history,” says David Phillips, deputy scientist-in-charge at Hawaiian Volcano Observatory. “It’s very rare for freshwater lakes to form in Hawai‘i, especially on the Big Island, because the ground is so porous.” The Kīlauea caldera is now so deep it penetrates the water table. Rainwater filters through the volcanic rock to feed the lake, which is 130 feet deep, 800 feet long and growing. Just shy of boiling, the moderately acidic water contains high concentrations of dissolved sulfur and magnesium. Samples of rock ejected during the collapse suggest that a similar lake might have existed in the past. Scientists looked for—and found—supporting evidence for this in traditional Hawaiian chants.

In one, a supernatural lizard named Kalamainu‘u attempts to vanquish Pele, the volcano goddess, by filling her caldera with phlegm. In another story, the pig god Kamapua‘a, Pele’s on-again, off-again lover, tries to flood Kīlauea with water to extinguish her volcanic fire. And in the epic tale of Hiʻiakaikapoliopele, one of Pele’s sisters shakes Kīlauea to its core while searching for her murdered husband. The heartbroken goddess jumps into the caldera, stomps her feet and cracks the top layer of the crater floor. Seeking to retrieve her lover’s spirit, she stomps again and again, shattering layers of earth in her rage—a geological scenario not unlike the continuous quakes of 2018. Geologists theorize that this story might have been inspired by a caldera collapse around 1500 CE.

These days the volcano-curious can view interactive graphics of Kīlauea’s caldera and new lake on the national park’s web site (URL below). “The depth of the crater gives us a window into the inside of the volcano,” says Phillips. “When you’re on the edge looking in, it’s just overwhelming.”