Rocks from the east rim of Kīlauea Volcano’s summit vent fell into the lava lake at 10:02 p.m., HST, on Saturday, August 6, triggering an explosive event that hurled fragments of molten and solid rock onto the rim of Halemaʻumaʻu Crater.
A light-colored “scar” about 20 m (66 ft) across from this rockfall is visible to the right of the spattering area on the lake surface. Rocks in the vent wall can become unstable when the level of the lava lake drops, as has been going on for the last several days.
The explosive event blanketed the rim of Halemaʻumaʻu Crater with a layer of tephra (volcanic rock fragments) up to about 20 cm (8 in) thick. The tephra deposit was thickest to the east of the former visitor overlook on the crater rim (shown here), where it formed a continuous layer.
Bombs were thrown up to 90 m (295 ft) beyond the crater rim at the overlook and were deposited over an area 220 m (720 ft) wide along the rim. Saturday night’s explosive event is a reminder of why this area remains closed. Had anyone been standing in this area when it occurred, that person would have been severely burned or killed by the falling debris.
Tephra blasted from the summit vent on Saturday night included lithic (solid rock) fragments from the vent wall as well as spatter (molten lava fragments) ejected from the lava lake. The light-colored lithic in the center of this photo is about 20 cm (8 in) long—the GPS unit is shown for scale.
Tephra, the general term for volcanic rock fragments exploded or carried into the air during an eruption, can range from dust-size particles to fragments more than 1 m (3.2 ft) in diameter.
In areas not completely blanketed by tephra from the explosive event, impact marks were obvious where large fragments of molten lava (spatter) had landed on the rim of Halemaʻumaʻu Crater, then bounced or slid to their current positions.
Volcano monitoring equipment installed on the rim of Halemaʻumaʻu Crater was a casualty of Saturday night’s explosive event.
This pile of charred wires and metal components, surrounded by melted plastic, is all that remains of the power supply for one of HVO’s gravity instruments located about 24 m (80 ft) from the crater rim.