KAMCHATKA. 129 



plane of denudation. These rocks may very probably be similar to those 

 of Petrapavlovsk, but they were not examined. 



Diagramatically the general structure of this part of the Kamchatka 

 peninsula may be represented as above, but it must be understood that 

 the illustration is not an actual drawing of any one part of the coast. 

 The order in time of the origin of its several features, as indicated by the 

 form of the land and with reference merely to their relative age, being as 

 follows : 



1. Stratified rocks, upturned, and denuded into systems of hills. 



2. Prolonged depression of 600 to 800 feet, during which a plane of 

 marine denudation was formed, while the sculpture of the inland hills 

 continued. 



3. Elevation of the land to within, say, one hundred feet of its present 

 level, during which narrow valleys were cut out across the plane of 

 marine denudation. 



4. Further elevation of the land to about the present level, after which 

 wide delta flats have been formed, as, for instance, that in the bay west 

 of cape Japounski and that about the mouth of the Avacha river. 

 These are so well marked as to indicate a considerable lapse of time. 



Figure i.— Diagram illustrating the orographic Characters of the southern Part of Kamchatka. 



The towering volcanic cones must, of course, have been formed at a 

 comparatively late date in this history, and their growth has continued 

 up to the present. 



Avacha bay, entered by a narrow strait, expands within to a wide body 

 of water from six to ten miles across. The little harbor of Petrapavlovsk 

 is situated on the east side of the bay. 



The rocks met with about this harbor are well stratified, often in regular 

 layers a few inches only in thickness. They consist of gray, black and 

 greenish felsites, hard argillites, generally very fine grained, associated 

 with gray, blackish or greenish halleflinta and greenish diabase or chlo- 

 ritic rocks, generally schistose. All these are much indurated and con- 

 siderably disturbed, sometimes, for limited areas, actually contorted. 

 They arc frequently broken by small faults, as well as by innumerable 

 joints, cutting in all directions, so as to shatter easily under the hammer 

 and to form by weathering rubbly slopes. While these rocks are evi- 

 dently in part composed of ancient volcanic materials, they must have 



