1909.] OUTLOOK OF SEISMIC GEOLOGY. 299 



— The studies of earthquakes during the last few years have done 

 much to destroy the ilkisions of more than half a century. Since 

 the time of Lyell, the burden of all geological instruction has been 

 the extreme slowness of terrestrial dynamic processes. Oscillations 

 of level described as slow and uniform warpings of the crust, had 

 been gauged by measurement upon shores, which in the expressive 

 language of de Montessus are dead, and where in consequence earth- 

 quakes are seldom or never left. If movements accomplished within 

 a week and largely upon a single day, can elevate stretches of coast 

 over 47 feet, as was true of portions of the Alaskan coast in 1899, 

 what modifications of our traditional theories will be required ! 

 There is a pressing need for extended studies on rising coasts to 

 determine by some scale the rate of elevation. 



Now it happens that one of the most rapid of erosional processes 

 is that accomplished by the waves as they beat upon a lee shore, and 

 this process is one capable of fairly accurate quantitative measure- 

 ment. The Pacific coast of North and South America, the greater 

 part of the way from Alaska to Patagonia, has, during a recent 

 period, been rising to the accompaniment of earth shocks. As we 

 now understand, these uplifts have been mainly spasmodic, and 

 the strand-lines abandoned with each successive uplift now stand 

 revealed in a series of steps or terraces, which, when closely 

 examined, reveal the characteristic marks of wave action sometimes 

 at heights of fifteen hundred feet and more (see Fig. 7, and Plates 

 XA\ and XVI.). Careful maps prepared after correlation of these 

 strand lines throughout long distances when combined with precise 

 studies of the rate of wave cutting, could hardly fail to shed light 

 upon the broader problems of seismic geology. 



In some cases such abandoned shores now in an elevated posi- 

 tion reveal clearly that their uplift was sudden and that no interval 

 long enough to permit wave cutting separated it from the inaugura- 

 tion of the present level. Thus in figures 6 and 8 are represented 

 shores which might almost be described as fossilized earthquakes, 

 for the evidence is clear that the elevation took place in what was 

 essentially a single sudden stage and must have been accompanied 

 by a great quake. 



Seacoasts ofifer the best possible data for observation and meas- 



