The 1958 Lituya Bay Megatsunami: The Tallest Wave Ever Recorded
On the evening of July 9, 1958, three fishing boats were anchored in Lituya Bay, a remote glacial fjord on the Gulf of Alaska coast. At 10:15 PM local time, a magnitude 7.8 earthquake struck the Fairweather Fault, triggering a chain of events that would produce the tallest wave ever recorded in modern history and permanently change how scientists understand tsunamis.
A Wave That Rewrote the Record Books
The earthquake dislodged a massive section of the mountainside above Gilbert Inlet at the head of the bay. Roughly 30 million cubic meters of rock, approximately 90 million tons, broke loose and plummeted several hundred meters into the inlet below, striking the water with a force that displaced the bay on a geologic scale. The resulting megatsunami sent water surging up the opposite slope to a height of 524 meters, or 1,719 feet, stripping trees and soil from the hillside up to the elevation of a modern 170-story building. That runup remains the highest ever reliably documented.
The tremors were felt across more than 400,000 square miles of Alaska and Canada, reaching as far as Seattle and Whitehorse, Yukon. The sound of the initial rockfall impact was heard 80 kilometers away. According to NASA Earth Observatory, the damage scar carved into the hillside by the wave remains visible from space to this day.
What the Survivors Witnessed
Despite the catastrophic scale of the wave, most of those aboard the anchored boats survived. Howard Ulrich and his seven-year-old son were aboard the Edrie in a small inlet on the southern side of the bay. Ulrich watched from the deck as water erupted at the head of the bay and bore down on his boat two to three minutes later. The Edrie was lifted and carried, then swept back toward the center of the bay. Ulrich regained control and navigated out through secondary waves still reaching 20 feet high.
Bill and Vivian Swanson, anchored near the bay entrance, were carried up on the swell and swept over the spit separating the bay from the open ocean, their boat lifted high enough that they looked down at treetops below them. Both survived with minor injuries. Two other fishermen anchored elsewhere in the bay were killed, and their boat was never recovered.
Why the Wave Was So Massive
Research in the decades following the event established that the megatsunami was caused not by the earthquake's ground motion directly, but by the massive rockfall it triggered. The rock mass fell as a near-solid unit, striking the shallow sediment floor of Gilbert Inlet and displacing water upward in a violent surge. A 2010 analysis proposed that a second, larger slide followed almost immediately: the rockfall may have destabilized up to ten times its own volume in glacial sediment trapped beneath the adjacent Lituya Glacier, releasing it in a "dual slide" that compounded the wave's energy.
Lituya Bay had experienced similar events before, with tsunamis exceeding 100 feet recorded in 1854, 1899, and 1936. But the 1958 event was the first for which detailed measurements and firsthand survivor accounts existed. Scientists used those records to model how landslides, rockfalls, and glacial movement can generate waves far larger than those produced by underwater earthquakes alone, fundamentally expanding the recognized causes of tsunami-scale disasters.
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