Six unoccupied houses along North Carolina’s Outer Banks have collapsed into the ocean as Hurricanes Humberto and Imelda rumble in the Atlantic, the latest private beachfront structures to fall as sea levels rise due to global warming. A sixth in Buxton collapsed overnight, the park service said on its website. Ocean overwash on Tuesday also prompted the state Transportation Department to close a portion of North Carolina Highway 12 on Ocracoke Island. Eighteen privately owned houses have now collapsed on Seashore beaches since 2020, the park service said. The first 11 were north of Buxton in Rodanthe, but a Buxton home fell into the surf two weeks ago.