Essay on the formation of new landscapes

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A new landscape is elevated from the sea to no great heights, sloping towards the sea, and finally subjected to rainfall. On this land rain falls, the run off concentrates into lower parts. Running water begins to excavate channel for it. Tributary channels are cut.

Where the land surface is level, there will be swampy tracts by stagnant water. In depressions ponds and lakes will be formed. Running water on such an uplifted land begins strong vertical cutting down toward base level. Rivulets carve rills that become gullies and ravines.

Lastly, stream flow is concentrated into a few main streams that carve out well-separated V-shaped valleys. The depth of such valleys depends on the height of the new land above the base level. Remember that the larger part of the land surface at this stage is not eroded to any great extent and remains at the original elevation.

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Thus, most of the land still remains highly elevated. Therefore interfluves (land between two river valleys) are broad and flat. The steeper slopes or gradient of the stream channels cause waterfalls, cataracts and rapids.

Lakes and swamps develop on elevated parts of the land. The drainage system is poorly developed. From the mouth of the main rivers as well as their tributaries, down cutting proceeds and the valley development extends upstream farther and farther.

As a result of rapid down cutting, a gorge form of narrow and steep-sided valley results. The depth of gorge however depends on the elevation of the land surface above base level. Unconsolidated rocks assist in lateral erosion which broadens the gorge. Weathering is more effective in making the gorges broader.

The number of tributaries multiplies, so that the flat-topped interfluves are narrowed. At this stage head-ward erosion is dominant which results in the extension of tributaries. With the passage of time the streams cease their vertical down cutting and lateral erosion gains the upper hand.

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