Which one of the following statements correctly describes how stream terraces can form?
A)Base level drops; the stream aggrades its channel, and the former floodplain is left below the present elevation of the stream.
B)A temporary base level is eliminated; the stream downcuts upstream from the old temporary base level, and the former floodplain is left well above the present elevation of the stream.
C)Base level rises; the stream downcuts, and the old floodplain is left well above the elevation of the present-day channel.
D)A temporary base level is eliminated; the stream builds its channel upstream from the old temporary base level, and the former floodplain is left well above the present elevation of the stream.

Question

Quizplus · Accepted Answer

When a temporary base level (such as a dam or a glacier) is removed, the stream adjusts by downcutting its channel upstream from the old temporary base level, leaving the former floodplain well above the present elevation of the stream. This process results in the formation of stream terraces. Option A is incorrect because the stream would aggrade its channel if base level drops, leaving the former floodplain below the present elevation of the stream. Option C is incorrect because if the base level rises, the stream would cut into the old floodplain, leaving it below the elevation of the present-day channel. Option D is also incorrect because if the stream builds its channel upstream from the old temporary base level, the former floodplain would be left below the elevation of the present-day channel.

Which One of the Following Statements Correctly Describes How Stream