308 C. W. HAYES GEOLOGY OF NICARAGUA CANAL ROUTE 



The effect of these climatic conditions is seen in the topogra[)]iy which 

 ciiaracterizes the region west of the hike. The hills are extremely steep 

 and deeply gullied. At the mouth of each ravine there is an alluvial 

 cone, showing that a heavy load of coarse and fine detritus is moved hy 

 the occasional flood which the ravine carries. 



The depth of the residual material, the regolith, is also very much less 

 on the west side than it is on the east. This is doubtless due in part to 

 the fact that the conditions of rock weathering are less favorable in the 

 former than in the latter region, but it is also due in part to the more 

 favorable conditions under which the agents of degradation act. Both 

 of these factors, however, are directly dependent on climate. 



Another factor which on the west side may be effective in modifj'ing 

 topographic forms is wind erosion. During the dry season, when the 

 protecting vegetation has been removed by forest fires, the steady force 

 of the trade winds raises clouds of dust, and the total amount of trans- 

 portation effected by this agency must be very considerable. The effects 

 are most noticeable on the lake and ocean beaches, where the sand is 

 driven with great force and piled up in dunes. Roads on which there 

 is sufficient travel to keep down the vegetation are usually sunk below 

 the surface of the adjacent country. The track is often bordered b}'- a 

 vertical bank from 5 to 15 feet high, and a part of this erosion is doubt- 

 less due to wind action. 



Rock Formations 

 conditions foe study 



The geology of the region under consideration has been examined in 

 detail onl}^ in the vicinity of the route of the proposed canal. Even 

 where studied most carefully, the relations of the various rock formations 

 are extremely obscure. This obscurit}'' arises chiefly from the nature of 

 the exposures which must be depended on in making out these relations. 

 p]ast of the lake, rock exposures are very infrequent, and it is practically 

 impossible from them alone to determine the relations of the various 

 rock formations. The vegetation is so abundant that no distant views 

 can be obtained, and the information which can usually be derived from 

 a broad study of the topography is entirely wanting. The extreme 

 depths to which the rocks are decayed and the uniform mantle of red 

 clay which covers their outcrops efi'ectually conceal their distribution 

 and relations. The larger streams, as already explained, are chiefly 

 flowing in old valleys which they are now silting up. Since thev are 

 not corrading their beds, their channels furnish exposures of materials 

 other than alluvial only where the}' happen to impinge on the adjoining 



