1964 Alaska Earthquake: The Harbors That Slid Into the Sea

At 5:36 p.m. on Good Friday, 27 March 1964, the most powerful earthquake ever recorded in the United States struck southern Alaska. Magnitude 9.2. The ground shook for about four and a half minutes. In the port towns of Valdez and Seward, the deadliest danger was not the shaking. Within seconds, the waterfronts themselves, built on loose, water-soaked river deltas, slid into the fjords as submarine landslides. They took docks, rail yards and oil tanks with them and threw waves back onto the towns before the ground had stopped moving. At Valdez, the cargo ship Chena was lifted, heeled hard over and slammed down where the dock had been. About thirty people on the waterfront died. At Seward, burning oil spread across Resurrection Bay, and about half an hour later the regional tsunami arrived and carried the fire ashore. This is a calm, sourced reconstruction of how two harbors fell into the sea, why their waves came in minutes instead of hours, and why Valdez had to be rebuilt on new ground. We also cover Whittier and Chenega, where local landslide waves also struck within minutes, and the regional tsunami that crossed the Pacific to Kodiak, Oregon and Crescent City, California. WHAT IS SETTLED AND WHAT IS NOT • Settled: the time (5:36 p.m. AST), the magnitude (Mw 9.2), the waterfront failures at Valdez and Seward within seconds, and the timing of the local waves (within minutes; before the shaking ended). • Disputed: the total number of deaths. Sources give 129, 131 and 139. About nine in ten died in tsunamis, most of them in local landslide waves. Death counts for Valdez (30–33), Seward (11–13) and Crescent City (10–12) also differ by source. • Disputed: the Valdez slide volume (about 55 to 75 million cubic metres). • Disputed: the highest run-up near Valdez. We use 52 m / 170 ft, the high-water line in the USGS reports; some sources give 67 m for splash. • Still open: the exact sequence of the Valdez waves, the sources of some local tsunamis, and when the next great earthquake will trigger the next delta failure. Seismic surveys show older slide deposits beneath the 1964 one in Port Valdez. This is the sixth film in our series on landslide-generated waves. Watch Lituya Bay 1958 (episode 1) and Tracy Arm 2025 (episode 5) for two more Alaskan fjords where the wave started at the shoreline. CHAPTERS 0:00 Before the shaking stopped 0:37 Four and a half minutes: the M9.2 earthquake 1:24 Valdez: the dock, the Chena and the slide 2:34 Seward: a harbor on fire 3:36 Why the waves came so fast (Whittier and Chenega) 4:23 The wave that crossed the Pacific 4:43 What changed, and what we still don't know