Hawaii's Hōlei Sea Arch Has Collapsed: Why Scientists Saw It Coming

The 90-foot Hōlei sea arch on the Big Island of Hawaii has collapsed into the Pacific Ocean, the U.S. National Park Service confirmed Friday, October 2, 2026. The arch stood within Hawaii Volcanoes National Park. It formed about 550 years ago and was a widely photographed coastal feature. The Guardian

The timing is narrow. The arch was still standing on September 23, 2026, when the park closed for Tropical Storm Nolo. It had fallen by the night of September 27, 2026. Park officials said the collapse was expected, and they had tracked instability in the nearby cliffs for years. National Park Service

The arch formed when waves wore away ancient lava flows, working along cracks and softer rock until only a span remained, separated from the sea cliff. It was like a doorway left standing after the wall around it wore away. The U.S. Geological Survey calls this uneven wearing differential erosion, and linked the fall to that process. CNN

Damage had built up over years. Earthquakes during the 2018 Kīlauea eruption hurt the cliffs around the arch. In January 2020, new cracks forced closure of the original viewing area, and a safer viewing area opened three months later. Later in 2020, surf from Tropical Storm Darby broke a chunk of rock off the lower part of the arch. Each event left the arch thinner and weaker, but the overall shape held until late September.

The broader context here is the challenge of managing coastlines that do not stay still. Sea arches last only while the span and the cliff behind it erode at compatible rates. At Hōlei, earthquake shaking, heavy surf, and growing cracks shifted that balance over several years, in a pattern common for unstable cliffs: move visitors back, watch partial failure, then full collapse.

Looking at what this means for the park, the next steps are practical, not geological. Officials will need to reassess cliff-edge stability, viewing distances, and how the site is explained to visitors. Collapses also change the shape of the seafloor nearby and the supply of rock debris, though how long those changes last depends on how waves move the fallen material. For managers of active coasts, Hōlei points to early setbacks, steady crack monitoring, and clear messages that collapse is a question of when, not if.