Lake Shapes

Many lakes have characteristic shapes determined by their mode of origin that are only partly described by their parameters. The ratio of length over width can give information on whether a lake is rectangular, circular or ellipitical and high Dss can indicate a dendritic lake, but a simple descriptive word is usually better. Circular lakes (Ds near 1) are uncommon, but can be found in volcanic vents, in some deflation basins and in lakes due to meteoric impact. Subcircular lakes are more common and are associated with a variety of origins: volcanic craters, deflation basins, dolines, cirques, kettle-holes to name the more common ones. Ellipitical lakes are a special subgroup of these and are generally associated with wind deflation. Subrectangular elongate lakes generally are of structural origin or result for glacial erosion in valleys (piedmont lakes). Markedly dendritic lakes result from flooding of dissected valleys as in some coastal lagoons, some landside lakes and in many reservoirs. It is these in which Ds is high (>3). Triangular lakes also usually arise from flooding, usually either on floodplains or along coasts. These may be confused with circular lakes on length/width ratios, but not by their descriptor. Lunate (or new-moon shaped) lakes result from river meandering to form oxbows, and sometimes from asymmetrical placed subcones in volcanic craters. Highly irregular lakes are possible from the fusion of lake basins and in glacially scoured areas. These also may have high Dss.

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