LAKES

1. Lakes

Hollows of land where water accumulates exhibit considerable variation in size, shape, depth, and permanence. From expansive water bodies like the Caspian Sea, measuring 760 miles in length with a depth of 3,215 feet, to temporary or permanent freshwater lakes such as Lake Geneva and the Great Lakes of America, these features play a crucial role in Earth's geography.

Types of Lakes

1. Inland Drainage: Regions with low precipitation and intense evaporation often result in lakes with high salinity, like the Dead Sea. Conversely, lakes with low salinity, such as the Black Sea, receive numerous rivers.
2. Desert Lakes: Playas, characteristic of desert regions, may dry up due to unreliable rainfall. In hot deserts, lakes disappear through evaporation, percolation, and outflow.

2. Formation of Lakes

Earth Movement

• Tectonic Lakes: Earth movements, including warping, sagging, bending, and fracturing, contribute to the formation of lakes such as Lake Titicaca (in the intermontane plateau of the Andes) and the Caspian Sea, the world's largest lake.
• Rift Valley Lakes: Lakes like Tanganyika, Malawi, and the Dead Sea result from faulting and sinking of land within the East African Rift Valley.

Glacial Formation

• Cirque Lakes: These lakes, formed by glacial erosion, include armchair-shaped tarns like Red Tarn in the Lake District and ribbon lakes like Lake Ullswater.
• Kettle Lakes: Irregular lakes on morainic surfaces, formed by the melting of stagnant ice, are exemplified by the meres of Shropshire and Orkney.
• Rock-Hollow Lakes: Ice scouring by glaciers creates lakes found in Finland, a country often referred to as the "land of lakes."

Volcanic Activity

• Crater and Caldera Lakes: Volcanic explosions contribute to the formation of lakes like Crater Lake in the USA, Lake Toba in North Sumatra, and Lake Avernus near Naples.
• Lava Blocked Lake: Solidification of lava in volcanic areas forms lakes like the Sea of Galilee in the Jordan Valley.
• Subsidence of Volcanic Land Surface: Shallow depressions like Myvatn in Iceland result from the subsidence of volcanic land surfaces.

Erosion and Solution

• Karst Lakes: Rainwater's solvent action on limestone carves solution hollows, leading to long, narrow lakes as seen in Lac de Chaillexon in the Jura Mountains.
• Wind-Deflated Lakes: Deserts create playas and salt lakes through wind deflation, such as the Qattara Depression in Egypt and the Great Basin in Utah.

Depositional Features

• River Deposits: Oxbow lakes formed in floodplains by river deposits, like those in the Mississippi and Rio Grande regions.
• Marine Deposits: Isolated lagoons formed by spits and bars, often found in deltas like those of the Nile and Ganga rivers.

Human and Biological Activities

• Man-made Lakes: Artificial lakes created by concrete dams and reservoirs, like Lake Mead above Hoover Dam on the Colorado River, serve various purposes.
• Animal-created lakes: Beaver activity results in lakes like Beaver Lake in Yellowstone National Park, USA.

3. Lakes and Their Impact

• Great Lakes, such as the St. Lawrence waterways in the USA, serve as vital arteries of commerce.
• Lakes influence the establishment of early settlements, town sites, industries, and transportation routes, as evident in the Yangtze Basin's development in China.
•  Lakes like Thirlmere, Katrine, Vyrnwy, and Okhla Reservoir play crucial roles in supplying domestic water to cities like Manchester, Glasgow, Liverpool, and Delhi.
• Lakes such as the Niagara River, Catawba River, and Abu Bakar Dam contribute to hydroelectric power production in different regions.
• Dams for irrigation, like Sennar Dam and Hirakund Dam, facilitate agricultural activities but may suffer from defects.
• Lakes help maintain steady river flows by absorbing excess water during the rainy season, impacting regions like the Yangtze Kiang, Tonle Sap, and artificial reservoirs.
• Lakes influence local climates, with milder winters observed in regions east of Lake Erie, Ontario, and Huron. They also impact cloudiness, as seen in regions around large lakes like Lake Michigan and the Caspian Sea.
• Lakes provide a source of protein through freshwater fish, and some, like the Caspian Sea, yield minerals like common salt, borax, and gypsum.
• Scenic lakes, including Lake Geneva, Lucerne, Lugano, Como, Placid, Vaner, Vatter, and Taiping, attract tourists and serve as health resorts.