National Geographic : 1899 Jul
236 PHYSIOGRAPHY OF NICARAGUA CANAL ROUTE Summing up the foregoing state ments very briefly, it appears that the surface of the Nicaraguan depression consists of a broadly undulating plain formed by the erosion of streams flowing to the ; Pacific and to the Atlantic from low gaps at the divide. Above this plain are residual hills, most abundant at the axis of the isth mus, where the continental divide was formerly located, but increas ing in height along the axis to ward the north, where they merge With the mountains of northern Nicaragua, and finally, there are many valleys which have .been Scut in the surface of the plain by the erosion of streams after the Region had been elevated to a higher altitude. The lower por tions of these valleys have subse quently been drowned and silted Sup with. the formation of broad alluvial floodplains. W During most of the time in which these topographic features were being developed the Pacific coast had an outline very different From that which it has at present. Lakes Nicaragua and Managua Then had no existence, and the re gion which they now occupy was Sin part the basins of streams flow ing to the Pacific, in part open ocean, and in part a bay which then indented the Pacific coast and whose southern point was near the present island of Madera. The relations of the present and former coast lines are shown on the accompanying map, plate 6.