THE GREAT ALASKAN EARTHQUAKES OF 1899. 



By CHARLES DAVISON, Sc.D., F.G.S. 



On September tttli, U!')'), it was known in all 

 the scismological observatories of tlie world that a 

 violent earthquake had occurred in some distant 

 region on the previous evening. From the duration 

 of the tremors which preceded the large undulations 

 on the different records it was ascertained that 

 the origin of the earthquake must have been in 

 or near Alaska, and this determination was soon 

 verified by the arrival of meagre despatches from 

 the central part of the disturbed area. 



There for a time the matter rested. Tlie earth- 

 quake was evidently one of the first magnitude, or 

 it would not have been recorded in such distant 

 regions. The damage to property, liowever, was 

 insignificant, simply because there was little 

 property to destroj'. Nor was there any loss of 

 life, for the country is almost uninhabited. Indeed, 

 nearly six years elapsed before it became known 

 to scientific men that the earthquake presented 

 phenomena of the most unusual interest. Fortu- 

 nately, most of these phenomena left traces that 

 were still distinct in 1905, though others presented 

 features that were not recognised until a year or 

 two later. 



In the summer of 1905 a party of geologists sent 

 by the United States Geological Survey visited 

 Yakutat Bay. The party was under the direction 

 of the late Professor Ralph S. Tarr, with Mr. 

 Lawrence Martin as physiographic assistant. Very 

 early in their work they noticed dead mussels and 

 barnacles adhering to the cliff, far above the reach 

 of the present tides. Had the barnacles died many 

 years ago they would have lost their hold on the 

 rock, and indeed many of them had fallen on to 

 ledges below. It was therefore evident that, quite 

 recentl}', there must have been a considerable rise 

 of the land, and the observers at once, and as it 

 proved rightly, attributed the work of elevation to 

 the crustal movements which had caused the earth- 

 quakes of 1899. In 1906 Professor Tarr again 

 visited the district, intending to study the glaciers 

 farther to the west, but was unable to cross them 

 owing to their great advance and the unusually 

 crevassed condition of their surfaces. Further 

 observations on the effects of the earthquake on 

 the glaciers were made by Messrs. Tarr and Martin 

 in 1909, and again in the following year by Mr. 

 Martin. The very valuable report on the earth- 

 quake and its effects by these two capable observers 

 has recently been published by the Geological 

 Survey of the United States.* As the report, 

 however, is lengthy and somewhat inaccessible to 



Fnglisli readers, I propose in this article to give 

 a summarv of the principal facts observed, devoting 

 special attention to those features which dis- 

 tinguish the earthquake from most others with 

 which we are acquainted. These are (i) the 

 remarkable changes of level manifested in Yakutat 

 Bay, the maximum uplift amounting to more than 

 forty-seven feet, and (ii) the advance and crevassing 

 of the glaciers, which took place principally between 

 the years 1905 and 1910, and which may not yet 

 have come to an end. 



The earthquake disturbed the southern part of 

 Alaska, and especially that district in which the 

 average trend of the coast is nearly east and west. 

 The region surrounding Yakutat Bay was that in 

 which the severest shaking and the changes of 

 level were manifested. The disturbed area on 

 land contains two hundred and sixteen thousand 

 three hundred square miles ; but this can only 

 be about half the total disturbed area, which must 

 therefore be estimated at about four hundred and 

 thirty-two thousand square miles. But even this 

 amount, great as it is, must be too small; for the 

 earthquake was felt at two isolated places to the 

 west, which are respectively six hundred and 

 seventj' and seven hundred and thirty miles from 

 Yakutat Bay. Thus, if the boundary of the 

 disturbed area be regarded as a circle with a radius 

 of seven hundred miles, the total area shaken by 

 the earthquake must amount to about one and a 

 half million square miles. 



This figure alone gives us some conception of the 

 violence of the earthquake. It has seldom been 

 exceeded by any known disturbance. The great 

 Lisbon earthquake of 1755 disturbed an area of 

 not more than about two million square miles ; the 

 Assam earthquake of 1897, one of about one and 

 three-quarter million square miles ; the Kangra 

 (India) earthquake of 1905, one of about one and a 

 half million square miles. The largest known dis- 

 turbed area is that of the Charleston earthquake of 

 1 886, which must have shaken more than two and 

 three-quarter million square miles. This earthquake, 

 however, was not one of exceptional strength. It 

 merely owes its extensive area of perception to the 

 presence of a sensitive and intelligent population. 

 On the other hand, the great Japanese earthquake 

 of 1891 disturbed only three hundred and thirty 

 thousand square miles, the Californian earthquake 

 of 1906 about three hundred and seventy thousand 

 square miles, and the Messina earthquake of 

 1908 about two hundred thousand square miles. 



• " The Earthquakes of Yakutat Bay, Alaska, in September, I89c)." By R. S. Tarr and L. Martin. 



Professional Paper 69. 



U.S. Geol. Surv., 



168 



