Gilbert, Grove Karl (1843–1918)

Time and space represent perhaps the two most fundamental inputs to the explanation of landscape development and differentiation. In traditional qualitative models, time is the preeminent variable. However, if the landscape and/or its constitutive elements reflect some sort of instantaneous balance between the forces acting on it, or them, and surface resistance, then we are offered a fundamentally different starting point from which to examine their development. Geomorphological models dominated by a temporal perspective have been largely biological in tone; however, Grove Karl Gilbert, a contemporary of William Morris Davis, viewed landscapes from the perspective of physics and engineering. The great contrast between the two approaches is that a Davisian approach results in a time-dependent model of development, while that of Gilbert favors time-independent modeling. In the former, spatial variation is essentially a form of contamination; in the latter, time, be it absolute or relative, contaminates. Clearly, both time and space must be considered; however, the relative weight assigned to each influences the resulting perspective enormously.

Gilbert received enormous professional recognition while alive; however, his professional life followed a very different path from that of Davis. Working for the U.S. Geological Survey, he served as an administrator for lengthy periods. He also was not apparently very interested in integrating his ideas into a comprehensive model of landscape development. Finally, his profound commitment to physical and engineering principles did not resonate greatly with the dominantly qualitative and biologically inspired views of the time. Consequently, his enormous insights, while lauded during his professional lifetime, lay fallow for a long time after his death. It was not until the 1960s that John T. Hack reinvigorated Gilbert's legacy when he invoked it as the foundation for his own ideas of dynamic equilibrium.

Present-day geomorphology would not be what it is without Gilbert's seminal paper “Report on the Geology of the Henry Mountains.” Among Gilbert's many important conceptual contributions are “the law of uniform slope,” “the law of structure,” “the law of divides,” and “the tendency to equality of action, or to the establishment of dynamic equilibrium.” He also produced important methodological papers that may be seen as the clear forerunner of the concept of “multiple working hypotheses,” more commonly associated with its later formulation by T. C. Chamberlin.