Scientists at the Hawaiian Volcano Observatory said the floor of the crater dropped 377 feet, cracking open a fissure and allowing the lava to flow.
Kilauea has been in a constant state of eruption since 1983, but such surges of lava are rare, vulcanologists said.
Authorities closed access to the Chain of Craters Road and nearby coastal trails to visitors.
But news of the lava has brought a tourist boom to the Big Island, with some visitors hiring helicopters to get a birds-eye view of the fiery eruption.
For those unable to make it to Hawaii, the observatory has a new Webcam set up to show Internet visitors from around the world a view of the Kilauea’s ongoing activity.
Rather than having one large cone, Kilauea is what’s known as a shield volcano, with a wide-reaching base and a scattering of craters.