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Lake basins originate through a wide variety of natural and anthropogenic processes. Some of these processes are cataclysmic (volcanism), some are gradual and usually imperceptible (tectonic movement), while others (meteorite impact) are rare and extraordinary. To the human observer, most lakes are permanent features of the landscape. On a geologic time scale, by contrast, most lakes are fleeting and all are ultimately ephemeral. Although we have few opportunities to witness a lake's origin, the same set of lake-forming processes at work historically continue unimpeded today.

Three elements are common to the origin of every lake: (1) an environmental force, (2) a body of terrain reshaped by that force into a closed depression (basin), and (3) a water supply. These three elements have met on the landscape with immense frequency during the Earth's history and have given rise to an estimated 304 million natural lakes in existence today.

The first element in a lake's origin is an environmental force and is the facet of its natural history most commonly used by scientists to guide the general classification of lake basins. George Evelyn Hutchinson (1903-1991) provided one of the most extensive surveys available on the origins of lake basins in the first chapter of his four-volume series, A Treatise on Limnology. There he describes the formation of numerous distinct types of lake basins resulting from 11 principal environmental forces, including glacial, tectonic, volcanic, fluvial, organism behavior, chemical, wind, landslide, shoreline, meteorite, and organic accumulation.

The second element in a lake's origin concerns the specific process by which an environmental force reshapes terrain into a closed depression. This is the originating element conventionally used by scientists to name distinct types of lake basins. In the case of glacial force, for example, different names are given to basins scoured in bedrock versus those impounded by moraine. Scientists have also found it useful at times to organize lake basins quite broadly according to whether the terrain-shaping process works destructively, constructively, or obstructively. Destructive processes (glacial scouring) excavate depressions, constructive processes (moraine deposition) build rims that define depressions, while obstructive processes (landslide) build rims that barricade preexisting flows. An individual lake basin may be molded by more than one process. Because the Earth's terrain is so richly varied in its composition of soil, rock structure, and topographic relief, there are ceaseless opportunities for unique outcomes in the bathymetry and shoreline structure of lake basins.

A lake district refers to a set of lakes that share a principal originating force and that reside geographically in a defined setting on the landscape. Although individual basins in a lake district are generally of similar age and origin, they can differ exceptionally in size and shape. For example, the set of English Lake District basins shown in Figure 1 all originated at about the same time by glacial scouring. Their differences in shape and bathymetry illustrate how the interplay between an environmental force and the terrain under influence can change rapidly across small geographic distances.

The third element in a lake's origin is its water supply. Unlike the first two elements, water itself is not always present at a lake basin's inception. Water derives variously from ice, rivers, precipitation, groundwater, wetlands, and preexisting lakes. Water sources to lakes may shift radically through time. For instance, most glacial lakes that were filled originally

Area (km2)

Length (km)

Max-depth (m)

Mean depth (m)

Volume (m3)(106)

Area of drainage basin (km2)

1. Windermere

14.8

17

64

21.3

314.5

230.5

2. Ullswater

8.9

11.8

62.5

25.3

223.0

145.5

3. Derwent Water

5.3

4.6

22

5.5

29

82.7

4. Bassenthwaite Lake

5.3

6.2

19

5.3

27.9

237.9

5. Coniston Water

4.9

8.7

56

24.1

113.3

60.7

6. Haweswater

3.9

6.9

57

23.4

76.6

26.6

7. Thirlmere

3.3

6.0

46

16.1

52.5

29.3

8. Ennendale Water

3.0

3.8

42

17.8

53.2

44.1

9. Wastwater

2.9

4.8

76

39.7

115.6

48.5

10. Crummock Water

2.5

4.0

44

26.7

66.4

43.6

11. Esthwaite Water

1.0

2.5

15.5

6.4

6.4

17.1

12. Buttermere

0.9

2

28.6

16.6

15.2

16.9

13. Loweswater

0.6

1.8

16

8.4

5.4

8.9

14. Grasmere

0.6

1.6

21.5

7.7

4.9

27.9

Figure 1 Fourteen of the largest ice scour lakes in the English Lake District (shown blackened above) and their physical characteristics (associated table). Burgis MJ and Morris P (1987) The Natural History of Lakes. Cambridge: University of Cambridge. Reprinted by permission.

Figure 1 Fourteen of the largest ice scour lakes in the English Lake District (shown blackened above) and their physical characteristics (associated table). Burgis MJ and Morris P (1987) The Natural History of Lakes. Cambridge: University of Cambridge. Reprinted by permission.

by melt water are now maintained by alternative supplies (precipitation, groundwater). Scientists find it useful to differentiate between lakes connected to rivers (drainage lakes) versus those whose hydrology is reliant exclusively on precipitation and groundwater (seepage lakes). On a regional scale, water supply can be unstable, resetting the hydrological origin of a lake long after its geological birth. One prominent example of this phenomenon is Lake Victoria (Africa), which originated several hundred thousand years before present but was entirely dry as recently as 12 400 years ago.

Certain types of lake-building processes can be expected to dominate over others at any given moment in the Earth's history. In today's inventory of larger lakes, those whose surface areas are greater than 0.01 km2 (1 ha), approximately 90% have basin origins that trace to glacial, tectonic, or fluvial forces (Table 1). Of these, glacial force far outweighs the importance of all others. This contemporary bias owes to recent and widespread glaciation during the Pleistocene when ice sheets covered nearly 25% of the Earth's continents.

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