HILO, Hawai'i — A 5- to 10-acre chunk of a lava delta at the ocean in Hawai'i Volcanoes National Park collapsed into the sea Sunday, bombarding the area around the delta with hot lava and rock fragments, scientists reported.

Scientists regard the collapse at 12:47 p.m. on July 30 at the west side of the East Lae'apuki bench as a "relatively small" event because it dropped less than 15 percent of the 60-acre bench into the ocean.

However, the abrupt dropping of the cooled lava into the ocean showered debris about 130 feet inland toward a rope barricade parks officials put up to keep visitors away from the bench.

"There was no warning before this collapse, which lasted only a few minutes," said a written announcement from Hawaiian Volcano Observatory scientists. "Anyone caught on that part of the bench would have been unable to escape. The lesson? Heed the warnings and stay behind the ropes. They are there for a reason."

The coastal plain adjacent to the spot where the lava pours into the ocean at East Lae'apuki was closed to visitors for almost a year and was reopened in early June.

Since then, scientists report that "countless tourists" have crossed the barricade, and some walked down onto the active bench itself by way of a steep, rocky ramp at the western edge.

That dangerous journey is no longer possible since the bench at the base of the ramp collapsed into the ocean Sunday.

Parks officials and scientists urge visitors to remain behind the rope barricade because "significant hazards related to lava bench collapses still exist."

A 44-acre chunk of the bench collapsed on Nov. 28 in the same area, about two miles from the end of Chain of Craters Road.

Benches occur as lava flows onto the shoreline, building a rock shelf that lies on an unstable bed of volcanic black sand and boulders. Cracks often form at the inland part of the bench before a collapse.