Giant Waves in Lituya Bay, Alaska; USGS PP 354-C

Waves Between 1854 and 1916

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Waves Between 1854 And 1916

Eyewitness Accounts

When the writer first visited Lituya Bay in 1952 stories of "floods" were heard from several fishermen who anchored their boats in the bay. One described catastrophic floods caused by breaking of a glacial lake near the head of the bay in 1890 and again in 1928. Another mentioned a flood about 1899 that destroyed a native village and a fish saltery near the mouth of the bay, and a second flood about 1928, when Huscroft was living on Cenotaph Island. Others reported that both floods occurred after sharp earthquakes. It is clear now that these accounts referred at least in part to the 1936 and 1853-54 waves, but the mention of dates 1890-99, of earthquakes, and of a saltery near the mouth of the bay suggest the occurrence of another wave of intermediate age. In 1958 James Betts of Angoon, Alaska reported that his grandfather had experienced a flood or wave in Lituya Bay in 1899 (Tom Smith, oral communication, Aug. 1958). The writer has been unable to obtain further information on this report.

Other Evidence

Possible evidence for the occurrence of at least one giant wave in Lituya Bay between the 1853-54 wave and the 1936 waves was first noticed during the 1953 field investigation, on the north shore near the mouth of the creek draining from Fish Lake. At this locality, in a narrow belt midway between the 1936 and 1853-54 trimlines, the spruce and hemlock trees appeared to be a little smaller in average size than in the forest adjoining and just below the 1853-54 trimline. This impression was not tested at the time by sectioning the trees. In the course of later study of ground photographs taken in 1917, photographs of the north shore of the bay between Cenotaph Island and Gilbert Inlet (J. B. Mertie, nos. 604, 605, 619, and 620, U.S. Geological Survey Photolibrary, Denver) showed not only the 1853-54 trimline but also, in the interval about 0.8 to 1.8 miles west of Gilbert Inlet, a probable lower trimline that had about the same height and configuration as the 1936 trimline in the same area. This segment can be identified with certainty as a trimline 'on a photograph taken in 1894 by a Canadian Boundary Survey party (McArthur no. 128; print loaned by W. O. Field, Jr., Mar. 3, 1959). The lower trimline in this area shows faintly on the 1929 trilens photographs and on these can be traced westward along the north shore, with decreasing certainty, to the locality of the field observation near Fish Lake. The eastward extent of this trimline near Gilbert Inlet is also uncertain. It probably falls to or near the shoreline, as shown on figure 18, but the photograph taken in 1894 suggests that it may rise eastward to or nearly to the 1853-54 trimline in this area.

Possible trimlines that may be at least in part younger than the definitely identified trimline on the north shore are shown in ground photographs taken in 1916 by Trevor Davis (oral communication, July 1958) near Cascade Glacier and on the spurs southwest of Gilbert and Crillon Inlets, and in photographs of the north shore of Anchorage Cove taken in 1917 (Mertie nos. 98, 99). The supposed trimline at Cascade Glacier is recognizable on the 1929 trilens photographs and can be projected about a mile to the southeast as an irregular lower limit of scattered clumps and groves of spruce trees. A few scattered spruce trees of about the same size are standing below this line, however. None of these supposed trimlines shown on 1916 and later photographs can be recognized on the few copies of 1894 photographs that are available, but because of incomplete coverage and the poor quality of some of the prints, their existence at that time cannot be disproved.

Dates

The lower trimline definitely identified in a photograph of the north shore of Lituya Bay taken in 1894 indicates that at least one giant wave occurred before this date but later than the 1853-54 wave. The stage of vegetation growth below the lower trimline, as shown on the photograph, suggests that the trimline was formed about midway in the interval 1854 to 1894. Hence the "evidence of flooding and washing" noted in 1874 by Dall (1883, p. 203) may have resulted from this wave.

The other possible trimlines shown on 1916-17 photographs, on the basis of the previously mentioned unsubstantiated eyewitness account and on the basis of the stage of vegetation growth, are attributed tentatively to a wave occurring in 1899. The occurrence during that year of the great Yakutat Bay earthquakes and the report of a great amount of drift timber and muddy water in the ocean between Cape Fairweather and Yakutat 2 days after the largest of the earthquake shocks (Tarr and Martin, 1912, p. 79) are further evidence for this date. The absence of any reference to Lituya Bay among the many reports of those who experienced the Yakutat Bay earthquakes probably means either that no report was received by Tarr and Martin (1912, p. 65-68) or that no one was in Lituya Bay at that time, because the shocks were felt throughout a large area in southern Alaska and adjacent Canada.

Effects Of The Waves

The trimlines plotted on figure 18 were reconstructed, mainly from the 1916 photographs by Davis and the 1929 trilens photographs. Altitudes on the trimlines were obtained by transferring points by inspection to the 1948 vertical photographs, from which the approximate height above water level was then estimated or measured photogrammetrically. Trimlines formed by two different waves were tentatively identified. The older wave apparently destroyed all or nearly all vegetation up to a sharp trimline for a distance of 4 miles or more along the north shore. A maximum altitude of 80 feet and a maximum width of 2,100 feet back from the high-tide line were measured for this trimline. The younger wave destroyed vegetation to a maximum altitude of about 200 feet on the northeast shore of Crillon Inlet and to lesser heights on the spurs southwest of Gilbert and Crillon Inlets, and possibly to a height of a few feet on the north shore of Anchorage Cove. On the south shore of Lituya Bay, west of Mudslide Creek, destruction of vegetation by either wave, if any, must have been limited to a narrow zone bordering the beach. The total area of substantial destruction of vegetation below all of the tentatively identified trimlines in less than 0.4 square mile. Most of the evidence of destruction by the waves between 1854 and 1916 was removed by the 1936 wave and any remaining evidence was wiped out by the 1958 wave.

Nature And Cause Of The Waves

Photographs taken in 1894 by McArthur (nos. 105A, 128) show fresh, bare surfaces on the upper slopes of the northeast wall of Gilbert Inlet and the valley of Mudslide Creek, suggesting that slides had occurred in these areas not long before. It is doubtful that the older wave was generated by a slide from the northeast wall of Gilbert Inlet, because McArthur's photographs do not show a trimline on the opposite shore of Gilbert Inlet. By analogy with the 1958 wave, destruction of vegetation should have been greatest there. A slide in the valley of Mudslide Creek could account for the maximum known destruction obliquely opposite on the north shore of the bay, and also for the absence of a conspicuous trimline in the inlets at the head of the bay.

The trimline of the wave inferred to have occurred about 1899, as reconstructed from photographs, compares most closely in magnitude and configuration with the trimline of the 1936 waves. It seems likely, therefore, that the 1899 (?) wave was generated in Crillon Inlet, possibly by the same unknown mechanism that caused the 1936 waves. However, if a wave did occur at the time of one of the great earthquake shocks in 1899, displacement along the Fairweather fault warrants consideration as a possible cause. By analogy with the 1958 wave, a rockslide into Crillon Inlet must also be considered. St. Amand (1957, p. 1357-59) suggested that at least one of the earthquakes in 1899 resulted from movement on the Fairweather fault. Evidence in support of this suggestion was found by Tocher and Miller (1959) after the 1958 earthquake. New surface breaks were seen from the air near the scarps on Nunatak Fiord described by Tarr and Martin (1912, p. 37-40) ; along the Fairweather fault southeast of Lituya Bay much of the new breakage had taken place along old scarps. The few oblique photographs taken at the head of Lituya Bay at the turn of the century are not adequate to either prove or disprove the occurrence of a rockslide in Crillon Inlet.


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Created 3 August 2004, Last Update 01 July 2012

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