l.AWSON.] 



Coast of Northern California. 



249 



sea. The cliff at the rear faces away from the ocean, and the bench 

 is very probably the remnant of a stream terrace. 



On entering Humboldt County conditions become more favora- 

 ble for observation of the higher baselevel bench marks. Although 

 there are several peaks and ridges rising to elevations of from 3,000 

 to 4,000 feet, plateau and terrace effects are common features of the 

 topography at various altitudes from 2,100 feet downwards. The 

 terraces on the flanks of the peaks eastward and southeastward of 

 Point Delgada are particularly conspicuous at altitudes of about 

 1,500 feet or more. Farther north near Pennoyer's ranch there is 

 a plateau tract at an altitude of about 2,100 feet which can scarcely 

 be interpreted otherwise than as a portion of an ancient baseleveled 

 plain. 



In the valley of the Mattole River, near Petrolia, there are very 

 clear and unmistakable remnants of ancient flood-plains terracing 

 the valley at altitudes of from 500 to 700 feet. Far above this 

 there are, on either side of the valley, plateau-like ridges at eleva- 

 tions which are probably not far from 2,000 feet. Above these rise 

 peaks whose slopes are in sharp contrast with the plateau. Mount 

 Blank, a few miles southeast of Cape Mendocino, appears on the 

 Coast Survey chart as a plateau having a general elevation of 2,100 

 feet, with a few knobs rising to 2,200 feet. The most pronounced 

 and persistent baselevel bench mark of this part of the Humboldt 

 County coast is one which appears very constantly at between 900 

 and 1,000 feet. This is well displayed near Point Gorda as a wave- 

 cut terrace, dissected by the Four-mile Creek. A corresponding 

 terrace appears at the same altitude on the north side of the mouth 

 of the Mattole, and remnants of it are seen all the way to Cape 

 Mendocino. It is a striking feature of the seaward flanks of Mount 

 Blank. On the crest of the ridge which terminates in Cape Mendo- 

 cino, the coast road passes over the remnant of a gravel flood-plain 

 at an altitude of about 950 feet, and west of the road there are ter- 

 races to an altitude of about 100 feet above the plain. Bear River 

 is the modern representative of the ancient river which evolved this 

 flood-plain; in the descent to Bear River the gravels are traceable 

 down the sides of the canon to the present stream bed. Beyond 

 Bear River the road passes over Bear River Ridge at about the same 



