ABSTRACT

The writer first developed the techniques of geological interpretation of aerial photographs prior to 1930. Since then he has worked extensively in "flatland" regions of low dip as well as in more mountainous regions in many different places around the world. Certain basic assumptions should underlie the work of the geological interpreter of aerial photographs in the broad eroded continental areas. Two of the most important ones are as follows:

1. The assumption of more or less universal structural control of drainage patterns.

2. The assumption of almost universal superposition of drainage except for extremely local and minor streams. The proper use of these basic assumptions and other reliable generalizations in the interpretation of aerial photographs can yield important results in the geological discovery of structural anomalies which are quite obscure to other means of exploration.

The writer feels that one of the major advances in geological science during the last one-half century has been the use of vertical aerial photographs for geological exploration. The results of their use have been especially significant in the "flatland" regions of low dip, and the full significance is not yet apparent.