A study of the physiography of any district involves not only a consideration of the surface phenomena, but an examination of the materials composing that portion of the earth’s crust and an investigation of the subterranean forces to which they have been subjected. A steeply inclined valley wall may merely indicate a youthful period in the topographic cycle; may be the result of glaciation; may be due to some inherent bedrock structure or the inclination of certain strata, or may even have been caused by recent faulting.
In investigating any physiographic problem, therefore, all the available evidence which tends to elucidate the physiography should be considered, no matter how superficial or deep seated may be the materials or forces involved. It is thus that the domains of physiography and general geology encroach and overlap—but always to their mutual ad1 vantage. Nowhere has the writer found this better illustrated than . . .