Chapter 11Origin and Ages of Lakes

• Glacial• Tectonic• Volcanic• Riverine• Coastal• Solution• Reservoir

http://www.eeescience.utoledo.edu/Faculty/Gottgens/webpapers/Gottgens%20et%20al.%20WASP%201998.pdf

Glacial lakes

• Developed by an ice barrier– proglacial lakes)

• Developed by glacial erosion– Cirque and paternoster lakes,

fjords, and kettle or pothole lakes• Developed by glacial deposition

(moraines)• Developed by a mixture of

glacial activity

Summit Lake, Alaska

Cirque Lakes

Lake Seal, Tasmania

Paternoster lakes(Glacier National Park)

Fjords (Norway)

Kettle lakes (ex Dundee WI) formed when block of trapped glacial ice in accumulated till melted.

Plunge-pool lakes formed at the base of a waterfalls off retreating glaciers. melt water

Space-shuttle photograph of the Finger Lake district in western New York.http://www.geospectra.net/kite/ny_finger/finger.htm

Morainal damming formed the Finger Lakes, Lake Mendota (& many WI lakes)

Glacial Lakes

Polygon ponds, Arctic region (see book Fig. 11.18).

                                                                                                                         

Lake Baikal• Max depth 1,620 m• Length: 636 km• Width: 80 km• Shoreline length: 2,100 km• Volume: 23,600 km3 (almost 20% of the world’s surface fresh water, more than all five Great Lakes combined)

Tectonic Lakes (formed by deep earth crustal movements)

Lake Tanganyika

Graben lakes: multiple faults (see book Fig 11.19)

Rifting A geologic term that describes the process that occurs when land sinks between two parallel faults.

Lake ChadDepth: 2-3 mWatershed:lake = 604:1

African rift lakes

Lake Chad, which once straddled the borders of Chad, Niger, Nigeria and Cameroon, has shrunk by an estimated 95% since the mid 1960s, due to the growth of agriculture and declining rainfall. Image: Unep

Volcanic crater Lakes

(See also book Fig 11.20)

Riverine (or fluvial) lakes

Riverine lakes (book Fig 11.17): Dominant lake type at low latitudesOxbow, blocked-valley, floodplain lakes (varzea)

River meander becomes separated Oxbow lakes (billabong)

http://www.lmic.state.mn.us/gifs/wilkin_oxbow.jpg

Lakes with other origins

• Coastal lakes

• Solution (karst) lakes

• Reservoirs

Wintergarden, Florida

“Gator Lake”, Florida Everglades (1989)

Reservoirs