Landforms Created by River and Glacier system
- These are the deep natural underground cave formed by the erosion of rock, especially by the action of water
- These currents erode the river’s bed and create small depressions in it.
- These are drilled into the bed of a river and are cylindrical in nature.
- The diameter and depth vary from a few centimetres to meters.
- These are formed due to the whirling impact of the water current in the upper course of the river.
- In India, the potholes can be observed in the river bed of the Kukadi, Krishna and Godavari river in Maharashtra.
A representational picture is given below :
- In mountain ranges, you will find these types of valleys
- V-shaped valleys have steep valley walls with narrow valley floors
- V-Shaped valleys are deep river valleys with steep sides that look like a letter V, a diagram shown below will give you a better understanding
- These are generally formed by the result of erosion and withering by fast-flowing rivers and are generally formed in the upper course of the river.
- A deep and narrow valley with steep sides is called a Gorge.
- Many gorge are found in river Ulhas in Thane district in Maharashtra and the gorge of the river Narmada at Bhedaghat near Jabalpur in Madhya Pradesh are well known.
- Waterfalls are formed due to erosion of both hard rock and soft rock.
- As the river flows over the resistant rock, it falls onto the less resistant rock, eroding it and creating a greater height difference between the two rock types, producing the waterfall.
- Over thousands of years, the repeated collapse of the caprock and retreat of the waterfall produces a gorge of recession.
- Waterfalls exist because of the difference in rock types. When a river flows, it passes through many different rock types and when a river passes from a resistant rock bed to a softer one, it erodes softer one very quickly and at the junction between the rock types, it steepens its gradient.
- The highest waterfall in the world is Angel Falls in Venezuela (~800 m).
- The largest waterfall is the Chutes de Khone (Khone Falls) on the Mekong River in Laos.
- The Niagara Falls on the river Niagara and Jog falls in Karnataka on Sharavathi river are famous waterfalls.
Meanders and Ox-bow lakes:
Meanders are bends in a river that form as a river’s sinuosity increases.
- A meander forms when moving water in a stream erodes the outer banks and widens its valley, and the inner part of the river has less energy and deposits silt.
- Meanders form a snake-like pattern as the river flows across a fairly flat valley floor.
- The sinuosity of a river is a measurement of how much a river varies from a straight line.
- Meanders are formed due to lateral erosion and as the erosion increases over the period of time, the meanders in the river again start flowing in the straight line.
- Meanders formation is a self-intensifying process where a greater curvature results in more erosion of the bank which in turn results in greater curvature.
- Oxbow lakes are an evolution of meanders that undergo extensive deposition and erosion
- When the meanders cut from the main course and water accumulates in this pool then it resembles the shape of the oxbow.
- These are formed in the region where the Tributaries Rivers joins the main river.
- These are formed due to the deposition of material carried by the Tributaries Rivers.
- These flows come from a single point source at the apex of the fan, and over time move to occupy many positions on the fan surface.
- This deposition resembles the shape a Fan like plains
- These are formed due to the overflows of the river and flood in the nearby areas.
- It is an area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.
- Floodplains are made by downstream travelling meanders.
- Slit carried by the water gets deposited in flooded areas and formed flat plains on both sides of river.
- The Gangetic plain is a flood plain.
- It is an embankment built to prevent the overflow of a river by a ridge of sediment deposited naturally alongside a river by overflowing water.
- When a river floods, it deposits its load over the flood plain due to a dramatic drop in the river’s velocity as friction increases greatly.
- Repeated floods cause the mounds to build up and form levees.
- Delta is a term coined by Herodotus (The Father of History) after the Greek letter Delta because of the deltoid shaped at the mouth of the Nile river.
- A River delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water.
- This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot transport away the supplied sediment.
- Over a period of time, this deposition builds the characteristic geographic pattern of a river delta.
- Sunderbans delta of the Ganga River is the largest in the world.
Landform created by the actions of River
- A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation over many years.
- On an average day, a glacier moves 1 to 15 meters a day.
- There are two types of glaciers, Continental Glacier and Alpine or Mountain glacier
Landforms Created by Glacier:
- It is half-open steep-sided hollow at the head of a valley or on a mountainside, formed by glacial erosion.
- Cirques are created by glaciers, grinding an existing valley into a rounded shape with steep sides.
- The back wall of the cirque is like a high cliff and the floor is concave and huge in size. The total shape resembles an armchair.
- When a glacier melts completely, water accumulates in the cirque and forms a lake which is known as a tarn.
- U-shaped valleys, or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape, with steep, straight sides and a flat bottom
- As the erosion of the sides is greater than that of the floor, a valley is formed with vertical sides and a wide floor. This valley is called a U-Shaped valley.
- These valleys can be several thousand feet deep and tens of miles long.
- As a glacier moves downhill through a valley, usually with a stream running through it, the shape of the valley is transformed. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. This parabolic shape is caused by glacial erosion striving to decrease friction as much as possible
- It is a valley which is cut across by a deeper valley or a cliff.
- Hanging valleys are often associated with valley glaciers, joining the main valley along its sides.
- Hanging Valley Landforms Have 2 Main Characteristics - a valley that leads to another valley below and A cliff or steep wall below the meeting point
- They are the product of different rates of erosion between the main valley and the valleys that enter it along its sides.
- The tributaries are left high above the main valley, hanging on the edges, their rivers and streams entering the main valley by either a series of small waterfalls or a single impressive fall
- Geologically, a fjord is a long, narrow inlet with steep sides or cliffs, created by glacial erosion
- Fjords are common in Norway, Greenland and New Zealand.
- The material transported and deposited by a glacier is known as moraine.
- A mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity
- Zigzag hills, with many steep slopes, made up of long stretches of sand and gravel are called eskers.
- The oval-shaped hills of lesser height are called drumlins.
- There are 4 types of moraines – Lateral, Medial, Terminal and Ground
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