Megatsunami - History of The Hypothesis

History of The Hypothesis

Geologists searching for oil in Alaska in 1953 observed that in Lituya Bay, mature tree growth did not extend to the shoreline as it did in many other bays in the region. Rather, there was a band of younger trees closer to the shore. Forestry workers, glaciologists, and geographers call the boundary between these bands a trim line. Trees just above the trim line showed severe scarring on their seaward side, whilst those from below the trim line did not. The scientists hypothesized that there had been an unusually large wave or waves in the deep inlet. Because this is a recently deglaciated fjord with steep slopes and crossed by a major fault, one possibility was a landslide-generated tsunami.

On 9 July 1958, an earthquake of magnitude 7.7-8.3 (on the Richter scale) caused 90 million tonnes of rock and ice to drop into the deep water at the head of Lituya Bay. The block fell almost vertically and hit the water with sufficient force to create a wave approximately 524 metres (1,719 ft) high. Howard Ulrich and his son, Howard Jr., were in the bay in their fishing boat when they saw the wave. They both survived and reported that the wave carried their boat "over the trees" on one of the initial waves which washed them back into the bay, though the larger wave did not harm them much. A similar tsunami out at sea could come tens of kilometers inland.

This event and evidence of a potentially similar past event at the same location inspired the term megatsunami.

Read more about this topic:  Megatsunami

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