@currentlyinscience: The Hōlei Sea Arch formed roughly 550 years ago when an ancient lava flow met the ocean, and waves slowly carved it into the dramatic arch millions of visitors photographed at Hawai'i Volcanoes National Park. It collapsed sometime between September 23 and 28, likely during Tropical Storm Nolo, the result of "differential erosion," where the ocean wears away softer layers of lava faster than harder ones, combined with years of earthquake damage from the 2018 Kilauea eruption. Park officials had actually warned for years that the arch was unstable, even labeling it a "temporary display of nature's handiwork." The same ocean that spent five centuries building it took less than a week to take it back. Source: CNN, National Park Service, Yahoo News