Geography Chap 9 (Goh Cheng Leong + NCERT)

Chapter 9

Lakes

Formation and Origin of Lakes

Lakes formed by Earth Movement:

1) Tectonic Lakes:
   >Lake Titicaca= highest lake in world= Andes.
   >Caspian Sea.

2)Rift Valley Lakes:
  >sinking of land b/w two //^LL fault.
  >East African rift valley=Zambia+Malawi+Tanzania+Kenya+Ethiopia+readsea ---Israel+Jordan.
  >Lake Tanganyika= worlds deepest Lake.
  >dead sea= saline

Lake formed by Glaciation:

1)Cirque Lakes or Tarns:
  >cirques/Corries = Red Tarn
  >Ribbon Lake.
  >(Image ↓:)

2)Kettle Lake
  >Lake=created by depression by “moraines” suspended in outwash plain falls after melting of ice.
  >identity= irregular shape.
  >Kettle Lake in Scotland.
   >Image ↓:


 
3)Rock hollow Lakes:
  >Formation= ice mountain was there----caused depression====ice melted===Lake left
  >formed by  = ice scouring.
  >found in finland.
  >Image ↓:



4)Lakes due to Morainic damming of Valleys:
  >both = Laterla + Terminal “Morains” has potential to damn the valley.
  >Lake Windermere, UK.


5)Lakes due to deposition of glacial drifts
  >Lowland with predominant “Drumlins” + poor drainage = Lakes
  >N. Ireland.
  >Image ↓:

Lakes formed by Volcanic activity:
1)Crater and Caldera lakes:
  >Lake Oregon(USA) + Lake Toba(N. Sumatra) + Lake Avernus (Naples).

2)Lava-blocked Lakes:
  >When Lava flow solidifies in valley= forming lake.
  >Ex- Sea of Galilee è ,in Jordan valley..

3)Lake due to subsidence of volcanic land surface:
  >Crust of hollow Lava flow= Collapse. ==leaving shallow depression.
  >Myvatn (Iceland).


Lakes formed by erosion:

1)Karst Lake:
  >underlying “Limestone rock” dissolves ---inside caves collapse= Lakes=AKA Poljes.
  >water in wet period.
  >Lake Scutari (Yugoslavia).

2)wind deflated lakes:
  >Deflating action in =DESERT= creates hollow = Lakes.
  >Great basin of Utah (USA).
  >Qattara depression in Egypt.

Lakes formed by Depression:

1)due to river deposits:
  >Ox-bowlakes
 
2)Lakes due to Marine deposits:
  >wind + waves isolates lake from ocean =Lagoons
  >Generally found at the “Delta of long rivers =Ganga/Nile”
  >usually drained during = Low tides.
  >South west France= lots of Lagoons.
  >Images ↓:



3)Lakes due to Landslide, Screes and Avalanches:
  >AKA barrier Lake.
  >Land slide/ screes = blocks the RIVER è temp Lake.
  >short lived  Lake


Lakes formed by Human and Biological Activities

1)Man-Made Lakes:
  >Artificial====Dam construction ---reservoir lake behind.

2)Lakes made by Animals:
  >animals like “Beavers” ==lives in community= builds Dam.
  >These dams= Permanent in nature.
  >Beaver Lake (Yellowstone, USA)
 >Beavers Image ↓:


 >Beaves lake ↓:


3)Other types of Lakes:
  >by mining activities + some made for tourism

Lakes and Man

1)Means of communication:
  >Great lake of N. America = cheapest transport route.

2)Economic and Industrial development:
  >industrial development in HOMES district(Lakes: H=Huron + O=Ontario + M= Michigan + E=Erie + S= Superior)
  >In China = Poyang, Tung ting are lakes with industrial dev in “Wuhan, china)

3)Water Storage:
  >both Natural + Artificial = supplies water to town.
  >ex- Okhla lake(in basin of Yamuna) = supplies water to Delhhi.
  >Vetarna+ Vihar +Tulsi = to Bombay

4)Hydro electric power generation:
  >lakes in mountain + any other high head.

5)Agricultural purpose:
  >lakes when dries = leaves alluvial deposite= Fertile.
  >lakes in Dam===provide irrigation water.

6)Regulating River:
  >Lakes in the basin of a river ====Regulates the river
     >>Saves from flood = during excessive rain---water diverts to lake==reducing intensity.
     >>Save from Draught= when less water available ----lake hold water ----taken by moving river.
     >>Clean water= River carrying loads(clay, dust etc) is deposited to some extent.
  >Ex= Bhakra + Nangal Dams on Sutlej .

7) Moderation of Climate:
  >deep and large lakes===behaves as Ocean.
  >Oceanic effect= breezes + rain + moderating effect.

8) Source of Food:
  >source of protein = Fish, crabs etc
  >artificial lakes for fish breeding= prominent in China+ Japan.

9)Source of Minerals:
  >Borax = Na₂B₄O₇. H20 =sodium +Boron + osygen.
    >>Traditional extracted from = Lakes of J&K.
    >>Now = imported .
    >>used in =Insecticide + cosmetics + shaving cream etc

>Gypsum=== CaSO₄. 2H2O
    >>Lakes of Rajasthan + J&K + Gujrat.
    >>used in Cement + Plaster of Paris etc.

  >Rock Salt
  >Common Salt
 

10) Tourist attraction and Health resorts:
    >Dal lake