Weathering and Work of River Wel-Come Dept. of Geography Topic Weathering and Work of River Presented By –Asst. Prof. R.P.Chavan Dept. of Geography SSVPS Dhule’s late S.D.Patil alias Baburao dada arts, commerce & late M.D. Sisode science College Shindkheda dist.- Dhule (Maharashtra) INDIA

Chemical Weathering – Solution (Honey Comb Structure)

physical Weathering – exfoliation (onion typed weathering)

physical Weathering – exfoliation (onion typed weathering)

physical Weathering – exfoliation (onion typed weathering)

physical Weathering – Block disintegration

Weathering by Burrowing animals:

Weathering by plants:

Importance of Weathering Soli Formation Water Conservation: increase in infiltration, percolation of water in to the ground . B) Economical Importance:- Building, Construction of roads, Dams and others

River and River System:- Chapter: 2 WORK OF RIVER River and River System:- River is a mass of water flowing on slope along a definite course. The water flows higher to lower levels due to the earth gravitational force. River with its tributaries constitutes river system. The flow of water arranges itself in a hierarchical pattern. The stream network is like branching tree. Those braches on outer point they concede as first order streams. They do not have branches or tributaries. The junction of two first order streams will produce a second order stream. The third order streams are formed by union of two or more of second order. Drainage Density:- It is a ratio of the total length of all the streams in a single river system to the area drained by that river system.

Depositional Landforms of River Erosional Landforms of River ‘V’ shaped Valley George Rapids Water Fall Pot Holes Depositional Landforms of River Meanders and Ox-Bow-Lake Flood Plains and Levees Deltas

I) Land Forms associated with the Erosional Work of the River: 1) ‘V’ shaped Valley: ‘V’ shaped valley formed in upper course of course of a river due to downward cutting. The river valley which is come into existence is very deep and narrow. This valley is gradually widened due to continuous erosion work of river. Hence valley becomes wide at the upper side while valley floor remain narrow. This valley looks like English alphabet ‘V’ hence the name ‘V’ shaped valley. Eg. ‘V’ shaped valley formed by ‘Ulhas’ river near Khandala.

Photograph of ‘V’ shaped Valley:

Photograph of ‘V’ shaped Valley:

Photograph of ‘V’ shaped Valley:

Photograph of ‘V’ shaped Valley:

2) Gorge: Gorges are very deep and narrow valleys having wall like steep valley side. If the rocks in the river bed are hard then they are very less weathered by river. Gorges are formed due to active downward cutting of the valleys. Eg. Most of the rivers in the Himalaya have Gorges, Indus, Brahmaputra etc.

2) Gorge:

2) Gorge:

3) Rapids: If the river beds have alternate and tilted layer of soft and hard rock then the small numbers of steps are formed due to erosion of soft rocks layer. The river water flows with very high speed on these steps through river bed. This feature is known as rapids. Eg. Rapids are observed on Krishna River near Pachagani and are Ullas River near Khopoli.

4) Water Falls: Waterfall refers sudden fall of water. They develop in the upper course of river. They are existing in areas where soft rock is in the lower layer and hard rock is on the upper layers. The soft rocks are more easily eroded than the hard rock by river. As result, the difference between these two sections increases. This way waterfall develops. eg Niagara fall of North America, The Yenna falls near Mahabaleshwar in Maharashtra, the Jog falls on the Sharawati river, etc.

Photograph of Water Fall

Photograph of Water Fall

5) Pot holes: The small depression in rocky beds of the river is called Pot holes. The rocks in the river beds are eroded by river water. Hence after some period cracks and holes are develop in the rock. The erosional material which is carried by river water obstructed in joints and holes. These material whirls in joints and holes became they are deeper and widen. This way pot holes are developed in the rocky bed of river. The diameter of pot holes ranges from few cm to several meters. The depth of pot holes is far more than diameter. eg the pot holes are develop in the bed of Mutha river at Vitthalwadi near Pune and in the bed of Godawari near Nashik.

5) Pot holes:

5) Pot holes:

II) Land Forms associated with the Deposional Work of the River: When the river flows in a plain it widens its valley. When any obstruction comes in course of a river, river cannot flow in a straight course. It flows by taking turns to obstruct. This way many loop like bends and turns are come into existence whenever there comes the obstructions in the course of a river. The bends of longitudinal courses of the river known as meanders. The river erodes rapidly against the concave sides of the meanders the processes of erosion of concave sides and deposition of sediments on convex sides of meanders continue. Then the meander becomes almost circular in a course of time. The two ends of meanders come closer. Meanders & Ox-Bow -Lake:

Photograph of Meanders in River

2) Floods Plains and Levees: During the flood period water spread over a plain area in lower course of river. The load carried by river deposited in that area during this period. This way long flood plain is formed along the both bank of river. eg the flood plain of the Ganges, Hwange Ho, Mississippi etc.

3) Delta : The word ‘delta’ derived from the letter of the Greek Alphabet is written as ‘∆’. Many deltas are triangular. ‘Delta’ refers to the fan shaped alluvial track of land which is formed because of the deposition of sediments at the mouths of river where it meets to sea. A number of factors are necessary for the delta formation- River should have mountainous upper course. There should have weak tidal waves. There should not large lakes in the course of river. There should be weak ocean currents and waves. The river should have long plain so that is flows with very low velocity. The Godavari, the Krishna, the Nile, the Ganga, the Mississippi river have formed deltas.

Photograph of Delta at River Mouth

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