It all started with a magnitude 8.3 earthquake in July 1958. It shook the southern coast of Alaska. And it triggered a devastating tsunami. It ripped through the narrow body of water and killed five people. The colossal wave swept away trees on the steep slopes surrounding the bay. It was the largest wave in history.
Hermann Fritz is a professor of civil and environmental engineering at the Georgia Institute of Technology. He specializes in tsunamis and hurricanes. He says that larger waves may have existed, although there are no certainties.
Fritz authored a study in the journal Pure and Applied Geophysics who recreated the tsunami. He used a specialized scaled laboratory tank. He calculated a height of 150 m, making it higher than any recorded wave crest on Earth.
The extreme scale of the landslide provided the force to create such a large wave. But the shape of the bay is the real reason the wave was so high, Fritz said. Lituya Bay is a fjord, a long, narrow coastal inlet with steep sides. During a typical landslide-generated tsunami, the wave radiates in a fan shape. But the narrow shape and steep slopes of Lituya Bay channeled everything in one direction. It was pushed into the surrounding slopes, which is why it was so high, Fritz said.
Landslide-generated tsunamis are much rarer than tectonic tsunamis. “They can be very large near the source, but they decay quickly,” Fritz said. The wave slowed to no less than 100 m when it reached the narrow opening of the fjord.
The 1958 tsunami was not the first of its kind in Lituya Bay. Geologists had previously discovered evidence of smaller tsunamis that occurred there in 1853, 1854, and 1936. But all evidence of these was washed away by the much larger megatsunami. The largest wave in history washed away everything in its path.