As geological agents, lakes play an insignificant role in the gradation of the earth’s surface than other natural agencies like river, wind, glacier, sub-surface water, seas etc.
Excepting an inconspicuous degree of erosion brought about by lake water the geological action of lakes are mostly concerned with the deposition of sediments, since it acts as the depositional site for the detritus carried by the rivers and streams feeding the lake.
The movement of the water in lakes occurs in the form of waves, that emerge with strong winds, currents and wind tides, both high and low. Like that of marine bodies of water, the erosion of lakes consists of the abrasion of shores and near-shore parts of the lake floor.
Different types of lacustrine sediments are formed depending on a variety of factors, such as-
(i) the size, shape and depth of the lake basin;
(ii) the geological structure and composition of the surrounding basin;
(iv) climate etc.
Lacustrine deposits are classified into three types-
(a) Terrigenous deposits which consist of the fragmental material brought in by rivers and streams and the detritus formed by lake abrasion.
(b) Chemogenic deposits formed through chemical precipitation of various salts and colloids dissolved in water.
(c) Biogenic deposits formed due to accumulation of various organisms on lake floor.
Important Lakes of India
(a) In Peninsular India-
1. Coastal lakes – Chilika lake, Pulicat lake, Kayal lake.
2. Lonar lake-(In Maharashtra).
3. Sam bar lake-(In Rajsthan).
4. Dhands – (Small lakes of aeolian origin in Rajsthan).
5. Runn of kutch – (Marshy tract in Gujurat coast).
(b) In Extra-peninsula-
1. Lakes of Kashmir – Fresh water lake like Walur, Dal lake and saline lakes like Pangkong, Salt lake, Tsomoriri etc.
Lakes of kumaon – Lakes like Nainital and Bhimtal.