Another way in which rivers have been enabled to cut their way through opposing ranges of hills and even mountains is by occupying the district before the hills or mountains were made. Such streams are called antecedent and are denned as "those that during and for a time after a disturbance of their drainage area maintain the courses that they had taken before the disturbance." (Davis.) In this manner a stream originally consequent may become antecedent. The simplest case of antecedent drainage is where an area is uplifted without deformation and without changing the direction of the slopes. Under such circumstances all the streams retain their old channels, and simply gain renewed power to cut them into deeper trenches, down to the new base-level. Such streams are said to be revived. Revived streams which had begun to meander may be held in these windings and trench them into deep gorges. Even if the upheaval be accompanied by folding or deformation, one or more of the streams may persist in its ancient course, provided the folding be very slow and gradual, so that the river is able to cut down through the obstacles which are raised athwart its course. A revolving saw cuts its way through a log which is pushed against it, so the river cuts its way through the rising barrier.

If the latter be raised faster than the river can cut, then the stream will be dammed back into a lake, or will be diverted to a new course. Naturally, the great trunk rivers are more likely to hold their previous courses than the smaller streams.

A fine example of an antecedent river is the Columbia, of Washington and Oregon, which is deflected to the westward by the volcanic plateau of central Washington as far as the foot of the Cascade Mountains, where it turns southward, following the mountains for some distance, then it once more turns to the westward and cuts through the Cascades in a great canon. This course the river has maintained despite a differential uplift of thousands of feet, and probably also the rising of the Cascades athwart its course. The Snake River, a tributary of the Columbia, has cut a canon 6000 feet deep through lava and granite, through a slowly rising upwarp.

Several rivers in the Alps and Himalayas, which rise in the inner part of the ranges and cut their way out through deep chasms, are believed to be antecedent.