From the earliest times in human history the economic and industrial activities of man have been changing the natural features of the earth’s surface in many different ways, such as by constructing dams, by diverting the courses of rivers, by connecting oceans and seas with canals, by tunnels, by mining, by draining oil from the rocks containing it, and in many other ways modifying the natural course of geologic processes.
Much has been written concerning this material influence of man on the earth, but the opposite effect, that is, the influence of the earth on man, has received much less attention; and yet from primitive times it has been active. It seems proper therefore to note the action of geologic phenomena on man throughout the ages in which he has existed. These influences may be either beneficial or detrimental to man’s welfare; they may advance his physical and mental . . .