hydrological cycle and the point out it's physical and biological roles in maintaining the earth systems

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Cycle in the strictest sense refers to a sequence of events which returns to it's starting point.Hydrological cycle in simple words refers to the cyclic movement of water in air,water and land which takes place by the change in it's phase from liquid to gas and again ack to liquid or solid(ice state).
according to C.A.M.king(1996)- asystem is defined as a set of objects that are considered together by studying their relationships to each other and their individual attributes.
 
The earth system which is both an isolated system(those in which the boundaries for the input of energy and output or export of mass and matter are closed or fixed) on one hand and on the other hand.The functioning of the earth system is the sum of the simultaneous functioning of several subsystems of the earth system one of which is th hydrological cycle.

Water which is the cheif and only component of the hydrological cycle is the source of life on this planet.Not only that it covers 3 parts of the earth's surface ,it forms a part of the body weight of all organisms.For example:-some species of fungi has <=90% water in their body.thus,hydrological cycle plays an immense role in maintaining the earth systems.

Physical roles:-
Water has a property of high specific heat capacity.When water in the form of oean currents move polewards then it liberates heat energy which modifies the severe cold climate prevailing in higher latitudes in winter near the coastal areas which help to keep some of the sea ports open during the winter season.
 
Sea water also modifies ,builds landforms by it's erosional and depositional action.Exmple:-Delta,modification of sea facing cliffs.Moreover,rainwater filling on the slopes wash away layers of soil causing sheet erosion.Large rivers which contains high volume of water depending upon channel gradient which determines it's velocity and whether there would be resistance of the rock strata and the character of the joints upon which the river/stream is flowing.V-shapped valley is an example of erosional landform while a delta can be cited as an example of a depositional feature.

Water in the solid state also has it's own contribution in sculpturing the landscape.Example:-Glacial Till is a depositional landform.Ice scoured plain is an example of the erosive action by the ice caps.
Water also chemically reacts with certain soluble rock formong minerals like calcium carbonate which are found extensively in the Karst region and give shape to landforms.

In the Karst region water forms sink holes and dissapear underground.On their path underground they form limestone caves, pillars,stalactites etc.

Biological Roles:-
Biological roles include transpiration and evaporation which in their own way help the food chain or the other non-biological earth systems.

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