The Tracy Arm landslide sent a tsunami wave far up the opposite side of the fjord near South Sawyer Glacier. Credit: John Lyons/U.S. Geological Survey On the evening of Aug. 9, 2025, passengers on the Hanse Explorer finished taking selfies and videos of the South Sawyer Glacier, and the ship headed back down the fjord. Twelve hours later, a landslide from the adjacent mountain unexpectedly collapsed into the fjord, initiating the second-highest tsunami in recorded history. We conduct research on earthquakes and tsunamis at the Alaska Earthquake Center, and one of us serves as Alaska state seismologist . In a new study published in the journal Science with colleagues, we detail how that landslide sent water and debris 1,580 feet (481 meters) up the other side of the fjord—higher than the top floor of the Taipei 101 skyscraper —and then continued down Tracy Arm. The force of the water stripped the fjord's walls down to bare rock.…