A valley is a long narrow depression in the earth's crust, flanked by well defined ridges and usually due to the erosive action of rivers or glaciers but sometimes due to trough-faulting. The valley cut by vertical erosion is usually V-shaped in cross-section and irregular in its course, its gradient being punctuated by sudden drops and long shelves. These irregularities represent local base levels which are gradually removed by denudation, so that as the falls are worn back and lakes infilled the breaks in the profile are reduced. With lateral erosion and mass movement, the valley broadens. Deposition occurs as the gradient slackens, and floodplains fill the valley floor. Rejuvenation leaves remnants of old floodplains above the new ones in the form of terraces, the highest of which are the oldest. A lowering of the water-table may leave dry valleys, and sudden uplift may leave hanging valleys, while the flooding of valleys by the sea gives rias. Research Valley
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Research Valley