The 1958 Lituya Bay Megatsunami Free Essay Example, 2500 words

Geography of Lituya Bay Don Miller describes Lituya Bay as ‘a T-shaped tidal inlet that transects the coastal lowland and foothills belt bordering the Fairweather Range of the St. Elias Mountains, on the northeast shore of Alaska’ (Miller, 1960). The stem of the letter T is formed by the main body of the inlet, which is seven miles long and two miles wide, with Cenotaph Island in its central part; the upper part of the T, which had been about 3 miles long in 1958, is formed by two other inlets – Gilbert Inlet and Crillon Inlet. The fiord-like inner part of the bay is surrounded by steeply rising walls – to elevations between 2Â  200 and 3Â  400 feet in the foothills and over 6Â  000 feet in the Fairweather Range (Miller, 1960). The shores surrounding the main part of Lituya Bay are predominantly stony beaches; the adjacent areas rise more gently from the beaches at varying gradients (Miller, 1960; Pararas- Carayan-nis, 1999). Two glaciers - Lituya Glacier Fig. 2 Lituya Bay’s position on the map of Alaska and North Crillon Glacier - each one about 12 miles long and a mile wide, descend their fronts into the heads of Gilbert and Crillon Inlet respectively (Miller, 1960). We will write a custom essay sample on The 1958 Lituya Bay Megatsunami or any topic specifically for you Only $17.96 $11.86/pageorder now About half of the front of Lituya Glacier and two-thirds of the front of North Crillon Glacier had bordered low deltas, before the July 9 earthquake and the wave that followed. A long spit - La Chaussee Spit – encloses the outer part of the bay, ‘with only a very narrow entrance of about 700 – 800 feet, kept open by tidal currents’ (Pararas-Carayannis, 1999). Bathymetry of Lituya Bay Based on soundings taken until 1940 (U. S. Coast and Geodetic Survey, 1942), Miller recorded that the maximum depth of the bay, just south of Cenotaph Island, is 720 feet and the minimum or sill depth is 33 feet at mean lower low water in the entrance (Miller, 1960). Describing the geography of Lituya Bay, Miller specified that the tides are diurnal, with a mean and a maximum range of about 7 and 15 feet respectively, and cause currents ‘with a maximum velocity of nearly 14 statute miles per hour in the narrow entrance’ (Miller, 1960) According to Pararas-Carayannis, who relies on the same bathymetric surveys made until1940, the head of Lituya Bay is ‘a pronounced U-shaped trench with steep walls and a broad, flat floor sloping gently downward from the head of the bay to a maximum depth of 720 feet(220 meters) just south of Cenotaph Island’(Pararas-Carayannis, 1999). Fig. 3 Detailed map of head of Lituya Bay, showing site of the rockfall, landslides, changes in the shoreline (heavy dotted line), and extent of wave inundation (light dotted line) from the 1958 earthquake and the giant wave it triggered.