1958 Lituy Bay Megatsunami: Alaska's Historic Event

The Geological Standoff Between Glaciers and Mountains

On the night of July 9, 1958, a 7.8 magnitude earthquake triggered rocks and ice to plunge into Lituy Bay in Alaska. NFX historian, Elizabeth Coxhead. Describes it as a precipitate geological standoff between the the local glacier and the steep mountains surrounding the bay. The resulting domino effect created a tsunami much larger than any other recorded wave - one that would have towered above a cruise ship. At Lituy Bay, the geology is not just a quiet backdrop; it is the dominant player. Only a few decades ago, the site was a one mile wide field of ice. The earthquake was unprecedented, but the movements of the glaciers and the water beneath them were more dramatic. The bay has a narrow entrance and is surrounded by steep mountains. The geological forces and seismic activity caused the glacier and mountains to be at odds. Not only was the glacier pushed into the water, but water also flooded up the mountains.

Scientific Visualization, Historiographical Challenges

From a 2021 NFX reproduction of the Lituy Bay event, the impressive imagery of the 1958 Lituy Bay tsunami drew scientific conclusion on what might have triggered the event. According to Coxhead, scientists have reasoned the cause of the event to be a landslide that reached into the Lituy Bay. To demonstrate the scenario, the team performed a complex numerical model. This scientific visualization used Finite Element Analysis to visualize and analyze the geological factors. The process does not have a single agreed upon timeline or a database of events, and the scientific history itself is evolving. As a result, reconstructing the geological and historical details of events like the Lituy Bay tsunami is both art and science. There is a discrepancy among even the most emphatic academics about the causal effect of the landslide. While some contend that the landslide is the primary cause, others believe the ensuing water waves exacerbated the landslide. It is also possible that both geological mechanisms contributed to the disaster. Historical texts appear to agree that the earthquake was the catalyst.

The Design of the Lituy Bay, Alaska

Many tsunamis are caused by earthquakes, but for Lituy Bay in Alaska, the landscape played a critical role. It is this unique geography which made the Lituy Bay tsunami so monumental, which further explains why it may be confusing to geologists and historians alike. The steep walls of Lituy bay contained the force of the water, thereby amplifying the disaster. In contrast, many of the dams around the world are designed with spillways to release water. Unlike Lituy Bay, water spillways are designed with slopes that release water more gradually, thus avoiding rapid wave amplitude. The Lituy Bay spillway would have been a steep slope of about 60 degrees. Similar to how glaciers erode mountains, the Lituy Bay was carved over time, unlike the more commonly found gradual slopes and valleys. This narrow bay was a carving process done over many millennia that required precise geological conditions.

The Need For Accurate Visualizations

The historical reconstruction of the Lituy Bay tsunami is an example of a broader challenge facing geological scientists and historians. The increasing complexity of natural disasters will no doubt increase the need for accurate visualizations. However, many other catastrophic events - like earthquakes, volcanic eruptions, hurricanes, and wildfires - will also challenge our visualizations. Some research has shown that the landscape may have influenced the intensity of the Lituy Bay tsunami. Landforms play a critical role in amplifying the effects of some disasters, as well as providing barriers which can slow the spread. The tension between the rigid mountains and the glacier, as well as the looped dynamics of the water and the bay. These visualizations are beautiful, but they also provide an opportunity to understand some of the geological phenomena behind these disasters. The Lituy Bay case study strongly suggests the importance of understanding geomorphology, historical context, and visualizations for assessing these disasters.