554 H. W. FAIRBANKS 
rise from 400 to 1500 feet from open valleys which are but little 
elevated above tide level, and terminate in Morro Rock which 
rises out of the ocean to a height of nearly 600 feet. These are 
undoubtedly peaks of erosion, the hard crystalline rock of which 
they are composed weathering away much more slowly than 
the soft strata of the Golden Gate series in which they were 
intruded. 
The extensive valleys south of the Santa Lucia range are 
underlaid by the oldest sedimentary rocks (Golden Gate series) 
of the sheet and are, in their general features, of great antiquity 
compared with the abrupt mountain ranges on either hand. 
The valley block has acted practically as a unit since the period 
of disturbance giving rise to the Santa Lucia and Buchon 
ranges. 
The principal hydrographic basin is that of the Salinas. 
This stream flowing across the northeast corner of the area 
pursues a comparatively regular course until it empties into 
Monterey Bay. The remarkable thing, however, about the river 
is, that instead of flowing in the lowest depression between the 
Santa Lucia range and the granite mountains, it has cut a channel 
for a number of miles through the granite flowing in a canyon 
5OOmtou7Oo) tect) deep: ts meandering. Course m bring cuaitaaan 
places to the edge of the granite, where it receives tributary 
streams from the Santa Lucia. These transverse streams have 
so eroded their separating divides in the soft sandstones 
between the two ranges that they form an almost continuous 
valley which is strictly a continuation of the valley of the 
Salinas farther down. This is clearly a case of superimposed 
drainage, for when the course of the Salinas and its tributaries 
was originally outlined the present valley region must have 
been higher than the granite ridge. 
A similar superimposed drainage is to be observed in the 
case of the streams which flow southwesterly from the Santa 
Lucia range. These traverse the broad open stretches of the 
San Luis valley, which in its lower portion is not over 200 feet 
tJouR. GEOL., Vol. V, p. 576. 
