Landforms Created by River System

Landforms Created by River System

V-shaped Valley

A river flows with a greater velocity in the mountainous region, and big, pointed fragments of rock also flow with a great speed along with the water.

• The river bed is scoured and down-cutting starts, ultimately giving rise to a deep valley with steep sides — this valley is called a V-shaped valley.

• These valleys are found in mountainous regions.

Gorge

• A deep and narrow valley with steep sides is called a gorge.

• The gorge of the river Ulhas in Thane district (Maharashtra) and the gorge of the river Narmada at Bhedaghat (Madhya Pradesh) are well known.

• There are many gorges in the Himalayas.

Waterfall

If there are both hard (resistant) and soft (less resistant) rocks in the course of the river, the less resistant rock is eroded faster.

• The resistant rock does not erode easily.

• That is why the river falls with great speed from a cliff-like part of hard rock. This is called a waterfall.

• The Niagara Falls on the Niagara River is in North America.

Potholes

In areas where the river bed consists of hard rock, the stones are carried along with the river water due to the whirling impact of water.

• That is why holes of various shapes are formed in the rocky river bed.

• Such holes are called potholes.

• Many potholes are observed in the river bed of the Kukadi, Krishna, and Godavari in Maharashtra.

Meanders and Ox-bow Lakes

Meanders are formed by lateral erosion. As the erosion increases over time, the meanders in the river start flowing in a straight line.

• The loop previously formed then separates from the main course of the river.

• Water accumulates in this separated part.

• As this loop resembles an ox-bow, it is called an ox-bow Lake.

• It is formed due to the impounding of water in the abandoned meander loop.

Fan-shaped Plains

In the region near the source of a river, the tributaries joining the main river deposit materials carried by them on the banks of the main river.

• This deposition creates fan-like plains.

• They are called fan-shaped plains or alluvial fans.

Flood Plains

When, during the floods, the river water overflows its banks and spreads in the surrounding areas, the silt carried by the water gets deposited in those areas.

• This creates flat plains on both banks of the river.

• Plains created by this depositional work during floods are called floodplains.

• The Gangetic Plain is a floodplain

Natural Levees

When a river is ovoverfloodedits water crosses its banks. At that time, the speed of the water is reduced, and the pebbles and stones carried by the river get deposited near the banks.

• This high wall of deposited sediments is called a natural levee or natural embankment.

• Such levees are found on the banks of the Mississippi, the Huang-Ho, and the Southern bank of river Ganga.

Delta

Delta was coined by Herodotus (the Father of History) after the Greek letter delta (Δ) because of the deltoid shape at the mouth of the Nile.

• A delta is a landform formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river.

• Deltas are formed from the deposition of sediment carried by the river as the flow leaves the mouth of the river.

• Over time, this deposition builds the characteristic geographic pattern of a river delta.

Delta Region

• A river meets a sea or a lake. The silt carried by the river is deposited on the bed near its mouth.

• The area near the mouth of the river gets gradually filled up by this deposition, causing an obstruction for the river to flow in a single channel.

• It, therefore, splits into two branches and meets the sea.

Landforms Created by the Actions of a River

• Over a period of time, there is deposition also at the mouth of these branches. The main course of the river gets split into a network of small channels.

• These sub-channels are called Distributaries.

• A triangular region of innumerable distributaries is formed near the mouth of the river. This region is called the delta region.

• There are delta regions near the mouths of the rivers Godavari, Ganga, Nile, Mississippi, etc. Deltas are very fertile.

• The largest delta of the world is the 'Ganges Delta'/ 'Sunderbans Delta' (350 km).

Glacier

A mass of ice sliding down the slope from a snow-clad region is called a glacier. On average, a glacier moves 1 to 15 metres a day. While a glacier is moving, the friction of the ice at the bottom slows down the movement of the bottom layers.

There are two main types of glaciers:

1. Continental Glacier

2. Alpine Glacier

Continental Glacier

• An extensive sheet of ice spreading across a vast region sometimes begins to move due to the pressure of the ice.

• This moving sheet of ice is called a continental glacier.

• Such glaciers are seen in Antarctica and Greenland.

Alpine or Mountain Glacier

• There is a snowfield in the mountainous regions of the Himalayas, the Alps, the Andes, and the Rocky Mountains, etc.

• The ice accumulating in these areas starts sliding down the slopes.

• This mass of ice sliding down from the mountains is called a mountain glacier or an alpine glacier.

Iceberg

• Blocks of ice break off from the continental glaciers and float away into the sea.

• A block of ice floating in the sea is called an iceberg. These icebergs are huge.

• The density of ice being slightly less than that of water, only a small portion of an iceberg is seen above the water, while the rest is submerged.

Landforms of Glaciation

Various landforms are created due to the transportation, erosion, and deposition work of a glacier. Let us consider the major landforms thus created.

Cirque

• When the snow from mountain peaks slides, it gets deposited in a hollow, if there is one on any side of the peak.

• The accumulated snow starts sliding down the slope. This causes friction at the floor and sides of the hollow, enlarging it further. This is called a cirque.

• The back wall of a cirque is like a high cliff, and the floor is concave and huge. The shape resembles an armchair.

• When a glacier melts completely, water accumulates in the cirque and forms a lake known as a tarn.

Fiord

• Where the lower end of the trough is drowned by the sea, it forms a deep, steep-sided inlet called Fiord, as on the Norwegian and South Chilean Coasts.

U-shaped Valley

When a glacier flows through a valley in a mountainous region, the sides of the valley get eroded.

• Ice causes friction on the sides of the valley.

• As the erosion of the sides is greater than that of the floor, a valley with vertical sides and a wide floor is formed.

• This valley is called a U-shaped valley.

Hanging Valley

In the mountainous region, many tributaries join the main glacier.

• The quantity of ice in a tributary is comparatively smaller. Hence, it causes less friction.

• The valley of a tributary is at a higher level than that of the main glacier; the valley of the tributary appears to be hanging.

• That is why such a valley is called a hanging valley.

Moraine

The material transported and deposited by a glacier is known as moraine. Moraines are made up of pieces of rock shattered by frost action and are brought down the valley.

• Moraines are of the following types:

1. Lateral moraine

2. Medial moraine

3. Terminal moraine

4. Ground moraine

• After a glacier has melted, different landforms of deposition are seen.

• The oval-shaped hills of lesser height are called drumlins.

• Zig-zag hills, with many steep slopes, made up of long stretches of sand and gravel, are called eskers.

Final Thoughts

Rivers play a crucial role in shaping Earth's surface, creating diverse and fascinating landforms through erosion, transportation, and deposition. From the sharp V-shaped valleys and deep gorges carved in mountainous regions to the fertile flood plains and deltas formed by deposition, rivers leave a lasting imprint on landscapes.

Features like waterfalls, natural levees, and ox-bow lakes highlight the dynamic nature of river systems. These landforms not only enhance the natural beauty of our planet but also provide fertile soils for agriculture and serve as vital ecosystems for countless species.

Understanding these processes helps us appreciate how nature constantly transforms the Earth over time. It also emphasizes the need to preserve river systems to maintain their ecological and geographical importance.