A 1,500-foot tsunami took scientists by surprise. Now we know why it happened

Early in the morning on August 10, 2025, Christine Smith awoke in a boat anchored in an inlet along southeast Alaska’s glacier-threaded coast. Smith and her husband were leading a small cruise on their 65-foot wooden boat, the David B. Inclement weather had forced them to spend the night 50 miles from their planned anchor spot in Tracy Arm, a dramatic fjord to the southeast of Juneau. As the naturalist and chef on board, Smith prepared to make breakfast and write about the rainy, foggy conditions in her daily log. Her husband, the captain, got her attention, asking, “Have you ever seen this before?”

From the boat, they could see water foaming over a nearby sandbar and repeatedly surging over, then retreating from, large rocks on the shoreline. The tide should have been falling. Perplexed, Smith texted her friend Jackie Caplan-Auerbach to see if the Western Washington University seismologist might know if this odd ebbing and flowing could be the result of a nearby landslide.

From what Caplan-Auerbach and other scientists pieced together in the hours and days that followed, Smith learned that if the David B had anchored in Tracy Arm as planned, she and the others aboard would have been killed.