An explosion early Wednesday in the giant crater at the summit of erupting Kilauea volcano scattered rock debris over an area of about 75 acres, including a popular tourist lookout.
There were no reports of injuries or of people in the area during the 3 a.m. event.
The U.S. Geological Survey's Hawaiian Volcano Observatory initially reported it as an earthquake.
But the scientist in charge at the observatory said it was the first explosion in Kilauea's Halemaumau Crater since 1924.
Lava that has flowed from the erupting volcano for more than a quarter-century has been coming from the side of the volcano, not from the main crater.
Scientist-in-charge Jim Kauahikaua said rock debris from the blast covered a portion of Crater Rim Drive and damaged the crater overlook.