We usually expert a stream with a highly meandering course to be on a floodplain in wind valley. However, certain exhibit meandering channels that flow in steep, narrow valleys. Such meanders are called incised(incisum = to cut into) meanders. How do such features form?
Originally, the meanders probably developed on the flood plain of a stream that was relatively near base level. Then, a change in base level caused the stream to begin downcutting. One of two events could have occurred. Either base level dropped or the land upon which the river was flowing was uplifted. An example cf the first circumstance happened during the Ice Age when large quantities of water were withdrawn from the ocean and locked up in glaciers on land. The result was that sea level (ultimate base level) dropped, causing rivers flowing into the ocean to begin to downcut. Of course, this activity ceased at the close of the Ice Age when ice sheets melted and sea level rose. Regional uplift of the land, the second cause for incised meanders, is exemplified by the Colorado Plateau in the south- western United States. Here, as the plateau was gradually uplifted, numerous meandering rivers adjusted to being higher above base level by downcutting.
We usually expert a stream with a highly meandering course to be on a floodplain in wind valley. However, certain exhibit meandering channels that flow in steep, narrow valleys. Such meanders are called incised(incisum = to cut into) meanders. How do such features form? Originally, the meanders probably developed on the flood plain of a stream that was relatively near base level. Then, a change in base level caused the stream to begin downcutting. One of two events could have occurred. Either base level dropped or the land upon which the river was flowing was uplifted. An example cf the first circumstance happened during the Ice Age when large quantities of water were withdrawn from the ocean and locked up in glaciers on land. The result was that sea level (ultimate base level) dropped, causing rivers flowing into the ocean to begin to downcut. Of course, this activity ceased at the close of the Ice Age when ice sheets melted and sea level rose. Regional uplift of the land, the second cause for incised meanders, is exemplified by the Colorado Plateau in the south- western United States. Here, as the plateau was gradually uplifted, numerous meandering rivers adjusted to being higher above base level by downcutting.
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