This paper investigates the problem of the physical causes of the present shape and structure of the earth's surface features. A physical process, called orogenesis, is defined as the cause of the surface features of our planet. The several theories of this process are reviewed and criticized from the standpoint of a physicist.
The properties of continuous matter which could give rise to orogenesis can be divided into yielding and flowing. Theories assuming yielding within the orogenetic shell thus form one large group, those assuming flowing form another. Before treating each group of theories, the physical background necessary for a consistent analysis is discussed.
Finally, an outline is given of how much credit the different theories receive in literature. Only two theories are at all widely accepted, and a decision between these two theories can hardly be expected upon physical grounds until more specific data are known about the interior of the earth.