An aerial photo of the August 10, 2025 landslide taken from across the fjord during a U.S. Geological Survey field reconnaissance overflight on August 13, 2025. Note the trimline along the far side of the fjord, caused by the tsunami stripping the walls of vegetation. View direction is approximately north. Photo by Cyrus Read/U.S. Geological Survey Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. If you’re one of the roughly 1.6 million who took a cruise in Alaska last year, chances are you sailed through the Tracy Arm fjord. The picturesque, narrow fjord is a popular sightseeing area  and is part of the Tongass National Forest, about 40 to 50 miles south of the capital city of Juneau. In the early hours of August 10, 2025 , an enormous landslide triggered a massive tsunami down the fjord. The tsunami was 1,578-feet-tall, or one-and-a-half times the height of the Eiffel Tower.…