The 90-foot Hōlei Sea Arch in Hawaii Volcanoes National Park fell into the Pacific Ocean in late September. The collapse occurred while the park was closed due to Tropical Storm Nolo, leaving a void where a historic landmark once stood.
The four-day window of the Hōlei Sea Arch's disappearance
According to the National Park Service (NPS), the Hōlei Sea Arch was still intact on Wednesday, September 23, when Hawaii Volcanoes National Park shuttered its gates to protect visitors from Tropical Storm Nolo. However, when park officials reopened the facility on Monday, September 28, they discovered the basalt structure had completely vanished. Authorities believe the collapse took place sometime between September 23 and September 27.
The timing of the event has sparked a wave of reactions on social media, with some visitors reporting they arrived at the overlook shortly after the collapse only to find the iconic view missing. The NPS confirmed the loss via Facebook and Instagram, sharing before-and-after imagery that illustrates the sudden transformation of the Big Island's coastline.
How the 2018 Kīlauea eruption signaled the end
While the final collapse happened during a storm, the structural integrity of the Hōlei Sea Arch had been compromised for years. As reported by the National Park Service, the arch suffered major damage during the 2018 Kīlauea eruption, an event that accelerated the instability of the surrounding lava rock. This suggests that the arch was already in a state of critical failure long before Tropical Storm Nolo arrived.
The loss of the Hōlei Sea Arch is part of a broader, relentless cycle of creation and destruction inherent to the Hawaiian chain. The Big Island is the youngest of these islands, and its landscapes are characterized by rapid geological shifts. The arch's demise echoes the way volcanic coastlines globally are reclaimed by the sea, where the very forces that create these monuments—lava flows and wave action—eventually dismantle them.
Differential erosion and the 550-year lifespan of basalt
The Hōlei Sea Arch was formed roughly 550 years ago when ancient lava flows from one of the island's six volcanoes met the cliff edges. the NPS explains that the arch's lifespan was dictated by "differential erosion," a process where softer rock layers are worn away by the elements more quickly than harder, more resistant basalt.. This natural sculpting created the vault, but it also ensured the structure's eventual failure.
Beyond the chemical composition of the rock, the NPS notes that the arch was subjected to constant battering from turbulent surf and the persistent vibrations of earthquakes. These combined stressors created growing cracks in the 90-foot formation , making its collapse an inevitability rather than a surprise to park geologists.
Trespassing risks at the unstable cliff edges
Following the collapse, Hawaii Volcanoes National Park has issued urgent warnings for the public to avoid the former site of the Hōlei Sea Arch. The NPS warns that the remaining ocean cliffs are hihgly unstable and prone to sudden, unpredictable collapses that could trap or kill visitors and put first responders at severe risk.
Despite these warnings, reports and social media posts indicate that some individuals have been trespassing into restricted areas to see the wreckage. This raises a critical question that remains unaswered by official reports: exactly how much of the surrounding cliff face is now compromised? While the park has flagged the area as dangerous, the full extent of the current instability—and whether other nearby formations are at immediate risk of following the arch—has not been detailed in public briefings.
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