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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



tsunami in places undoubtedly increased the height to which the water 

 dashed on shore. Moreover, in other places, where the rise in water 

 level due to the tsunami was gentle, storm waves on top of the tsunami 

 were responsible for much of the damage. The generally greater vio- 

 lence of the waves on the windward (northern and northeastern) 

 coasts as compared to that on the leeward coasts may have been in 

 considerable part the result of the large storm waves which were driv- 

 ing in on the windward coasts. Places on the windward coasts which 

 were sheltered from the storm waves also experienced less violent 

 waves. Thus at Kalaupapa, on the sheltered side of the peninsula 

 on the windward side of Molokai, both photographs and the testimony 

 of observers indicate that the rise of 25 feet caused by the tsunami was 

 not violent. On the windward coasts, much of the rapid variation in 



Figure 5. — Map of the island of Molokai, showing heights (in feet above lower low 

 water) reached by the water during the tsunami of April 1, 1946. 



intensity of wave attack may have resulted from the caprice of storm 

 waves. 



Submarine topography. — Owing to their great wave length, the 

 waves were somewhat affected by the ocean bottom throughout their 

 course. However, the effect of the bottom increased greatly as the 

 waves moved into shallow water, and caused a slowing of the wave, 

 an increase in its height, and a steepening of its front. A direct evi- 

 dence of the increase in height of the waves in shallow water was 

 afforded by the lesser heights reached by the water at the ends of cer- 

 tain peninsulas projecting into deep water and not prolonged seaward 

 by pronounced ridges, as compared with the heights on adjacent shores 

 rising from shoal water. Thus at the end of Kalaupapa Peninsula, 

 on the northern coast of Molokai (fig. 5) , the water dashed only 7 feet 

 above normal sea level, distinctly less than do the waves of ordinary 

 storms ; whereas on the coasts rising from shoal water both east and 

 west of the peninsula, the water swept up to heights of 30 to 54 feet. 

 At the end of Keanae Peninsula, on the northern coast of Maui (fig. 6) , 



