It is customary in geological literature to apply the term fault to any dislocation of the rocks, in which the broken ends of the beds are carried past one another, yet, used in this manner, it includes structures of very different significance, produced in dissimilar ways. It therefore seems advisable to distinguish between the two main classes of structure by removing thrusts altogether from the category of faults. Used in this restricted sense, faults are those dislocations which generally tend toward the vertical and occur in horizontal, inclined, or but slightly folded strata, which, to all appearance, have been subjected to tension rather than compression, though the latter frequently occurs locally, while thrusts tend to be horizontal and are found in regions of violent compression. The classification of faults is even yet the subject of vigorous discussion, and no general agreement has been reached, so that the following scheme is to be taken as merely tentative, though it departs but little from the customary plan, except in the complete separation between thrusts and reversed faults, which has been advocated by many writers.

In the present state of knowledge, however, any scheme of classification has an undue appearance of exactness.

Dislocations

Faults

I. Radial

1. Normal

a. Strike

b. Dip

c. Oblique

2. Reversed

II. Horizonta

III. Pivotal

Thrusts

I. Scission

II. Fold

III. Surface