U. S. Geol. Surv.
Scale, 1+ mile per inch.
PARTS OF LOS ANGELES AND SAN BERNARDINO COUNTIES, CALIFORNIA.
Fig. 70.—The valley (canyon) of the Yellowstone. A young valley in an elevated region.
Fig. 71.—Mature erosion topography in a region of slight relief, Iowa. (Calvin.)
Fig. 72.—Mature erosion in a mountain region. From mouth of Gray Copper Gulch, Silverton, Colo., quadrangle. (Cross, U. S. Geol. Surv.)