Conceptual scheme for the evolution of landscape in a humid temperature climate. The transition from, late youth ti early maturity is marked by the disappearance of remnants of the initial surface and by smoothing (grading) of valley side-slopes. In early maturity, most of the landscape is occupied by valley side-slope; in late maturity, by the valley flats of streams. The dashed line on each block represents sea level.

Confined and unconfined aquifers. Artesian wells may be flowing or non-flowing depending on whether the pressure surface is above or below the ground surface. (A) Wells in an unconfined aquifer. (B) Artesian wells in a confined artesian aquifer. Zumberge, 1958, p. 135.

Conglomerate in Newark Series, N.Y. State Thruway, about 1 mile west of Spring Valley, Rockland County, N.Y.

Shows a close-up of a pipe being connected on oil rig, Rapdan oil field, Saskatchewan.

Contact between second interglacial (Leinan) laminated silt and uppermost till. See Wickenden, 1931b, section C. Near Stewart Valley, Sask. See also Christiansen (1959).

Contact between Upper Cretaceous Judith River (our Belly River) and the overlying Bearpaw shales. Near bridge crossing Missouri River along Malta-Lewistown highway, Montana, May, 1964.

The hypothesis of continental drift has been invoked by some geologists to explain the occurrence of Permo-Carbiniferous tillites in Africa, South America, Australia and India. Arrows show the direction of ice movement inferred from striations (Zumberge 1958, p. 277).

Contour map of Scripps and La Jolla submarine canyons. Shepard, 1960, p. 136.

Contracting earth. Cross section of the earth, illustrating areas of compression and tension and the level of no strain. Jacobs et al., 1959, p. 353.

Contracting earth. Formation of arcuate fracture due to contraction. Jacobs et al., 1959, p. 355.

Contrasted slope profiles. Widening of valleys and change of slope profile during the cycle of erosion. Right, youth to old age according to W.M. Davis. Left, with parallel scarp retreat, according to W. Penck. (From Davis, 1930). King, 1953.

Convection currents. Continental mountain chains and island arcs could form where currents sink and meet. Mid-ocean ridges where they rise and blocks are torn apart. Arrows indicate directions of horizontal flow of currents at present. Broken lines are faults (J.T. Wilson, 1963, Sci. Amer.)

Convection currents within earth's mantle are basis for a theory of the origin of the mid-ocean ridge and rift. As seen here, the currents flow up under the rift, push out new material, lover laterally under continents and compress them, making mountains rise up. Heezen, 1960.

Convergence of shark, ichthyosaurus, and dolphin. (Umbgrove, 1943, p. 79).

Coral reefs. Shift in coral reef belts on earth throughout time (Scwartbach, 1961, p. 412)