Landforms and their Evolution Notes in English Class 11 Geography Chapter-6 Book-Fundamental of Physical Geography

 

 

distinctive landforms created by various processes of erosion 

1. River 

• V shaped valley 

• Alluvial Sankhu 

• Alluvial fan 

• river meander 

• Oxbow Lake 

• Embankment 

• flood plain 

2. Ground water  

• Lepidge 

• perforation 

• Kandara 

• Blind Valley 

• tera rosa 

• Hummus 

3. Sea water  

• Coastal ledge 

• coastal cave 

• Stack 

• Pulin 

• Barrier 

• Coordinating blocker 

• Coast Line 

4. Himani 

• U shaped valley 

• hanging valley 

• Aerit 

• Snow Gower 

• mountain peak 

• Nunataka 

• moraine

• Sheep Rock  

5. Wind 

• aeruginosa 

• umbrella shell 

• Jyumen 

• Yardang 

• domed mound 

• sand dune 

• Loess 

• Playa 

Landform 

• Landforms are small to medium sized landforms. 

• This is the physical form located on the surface of the earth.

Landscape

• Several landforms combine to form a broad landscape.

• A landscape is a large set of landforms that represents a broad portion of the geosphere.

• Landforms are created through the erosion and deposition of various geological processes and factors such as running water, groundwater, wind, glaciers, and waves.

• Landforms change over time due to the influence of geomorphic processes. 

• Every landform has a beginning, and then changes in size, shape, and nature.

• Changes in climate affect the intensity of geomorphological processes. 

• The vertical movement of biospheres can cause modification of landforms.

running water 

• In humid regions where there is excessive rainfall, the most important geomorphological factor that causes surface degradation is erosion.

1. Layer flow 

• how to sail on wide and narrow paths

2. Linear flow

• It flows in valleys in the form of rivers and streams.

conditions of flowing water 

1. Puberty

• Rivers create shallow valleys.

• Floodplains are narrow or absent.

• Watersheds are wide and flat, containing swamps and lakes.

• When hard rocks are exposed, waterfalls and rapids are formed.

2. Adulthood  

• The rivers have large volumes of water, and the tributaries join together to form V-shaped valleys.

• The main river flows across a wide flood plain.

• Waterfalls and rapids disappear.

3. Old age 

• The rivers flow freely across wide floodplains.

• The dividers are flat, in which lakes and swamps are found.

• The landforms are at or slightly above sea level.

Degradative spatial formations = valleys  

• The valleys begin with narrow and small streams.

• These streams turn into long and wide ravines, which over time become deeper, wider, and longer to form valleys.

Types of valleys 

V shaped valley 

• These valleys are formed due to the continuous erosion process of the river.

Gorge 

• A deep, narrow canyon.

• Both sides have steep slopes.

• The bottom and top parts have the same width.

• Formed in hard rocks.

Kenyon

• Deep valley like a gorge.

• Steeply sloping banks  have a top portion that is wider than the bottom.        

• Formed in horizontal stratification of sedimentary rocks.

Of the water trough 

• Small pieces of rock eroded on the river bed move in a circular motion.

• The size of these depressions increases over time, causing the river valley to deepen.

depressed 

• Pond: Deep ponds formed by the falling of water and the circular rotation of the rocks.

subungual erysipelas

• These are river bends which are deep cuts in the river bed.

• This usually occurs in hard rocks.

• There are deep bends in the bed, but the gradient of the river is generally low.

severe erysipelas

• These are river bends that occur in flood or delta plains.

• These usually occur in flood plains and delta areas where the river gradient is very gentle.

• The river bends here are more curved and wider, and are formed as a result of more abrasion.

River Terraces

• These mark the bottoms of old river valleys or flood plains.

• These are eroded lands, formed by perpendicular erosion of river deposited flood plains.

• River altars can be at different heights.

Paired altars

• Altars of equal height on both sides of the river.

Alluvial fan 

• Alluvial fans are formed when a river flows from higher elevations into gently sloping plains and deposits soil and rocks there.

• When the river flows through mountainous areas, it brings huge amounts of soil and rocks.

• When the river comes to gentle sloping plains, it cannot carry its load (soil and rocks).

• Therefore, this material gets deposited in the shape of a cone, which is called alluvial fan.

• The rivers which flow from alluvial fans often do not flow very far along their original course but change their course and divide into many branches called distributaries.

Delta

• A delta is an area where a river dumps the material it has carried into the sea, leaving behind a cone-shaped area.

• In this the deposition of material is systematic, with coarser particles being deposited on the shore and finer particles in the sea.

Floodplains

• Floodplains are areas that form along river banks when material is deposited during floods.

• When the river changes from a steep slope to a gentle slope, larger objects are already deposited on the banks.

• They are built at a height and are not affected by flood water. 

• These are formed by flood deposits and river deposits.

• The old river channel gets filled up and solid material gets deposited there.

river meander 

• Floodplains are areas that form along river banks when material is deposited during floods.

• When the river changes from a steep slope to a gentle slope, larger objects are already deposited on the banks.

• They are built at a height and are not affected by flood water. 

• These are formed by flood deposits and river deposits.

• The old river channel gets filled up and solid material gets deposited there.

ground water 

• Groundwater is water that is hidden beneath rocks and plays a role in rock erosion and landform formation through various processes.

कन्दरा/गुफा  

• There are limestone and dolomite rocks between the rocks and the water seeps through the cracks and joints and flows horizontally along the stratification of the rocks.

• Vacant spaces are created by the dissolution of limestone rocks.

• These spaces form long and narrow tunnels.

Glacier

• The ice mass flowing on the earth in the form of a layer or as a linear flow from mountain slopes into valleys is called a glacier.

• Glaciers can flow anywhere from a few centimetres or less to a few metres per day. 

• Glaciers move mainly due to gravity.

• Glaciers cause strong erosion due to the friction generated by their own weight.

Sark

• In the upper part of the glacier, erosion takes place on the bed, which forms troughs with steep sides, which are called cirques. 

Horn

• When two circles meet each other in opposite directions, a pointed peak-like shape is formed, which is called a horn.  

Aret

• Due to continuous erosion the walls on either side of the cirque become tight and it is shaped like a comb or saw like ridges called arets (sharp ridges). 

• Their upper part is pointed and their outer shape is crooked. 

• Climbing these ridges is often impossible.

Glacial valleys/troughs

• They are U shaped.

• The bottom is broad and the edges are smooth.

• The slope is steep.

• The debris is scattered in the valley or the moraine debris is in the form of a swamp.

• Lakes emerge on the rocky surface.

What are Moraines   ?

• A pile of debris and soil left behind by a glacier.

Type:

1. The last snow

• Long piles of debris deposited at the end of the glacier.

2. Parietal moraine

• Stacks built into the side of a glacial valley wall.

3. Lateral moraine

• Together with the terminal moraine they form horseshoe or crescent shaped mounds.

4. Planar moraine

• A layer of debris deposited on the valley floor, formed when a glacier melts.

5. Medial moraine

• Stacks formed in association with lateral moraines in the middle of the valley, which are less obvious.

Esker

• There are piles of debris and rocks accumulated beneath the ice, which become visible after the ice melts.

• In summer the glacier melts and the water flows over the ice and also seeps down through holes in the ice.

• This water collects beneath the glacier and flows as a river beneath the ice.

• This water brings large boulders, rock fragments and debris, which get deposited beneath the ice.

• After the ice melts, these debris appear as curved piles, called eskers.

Himani Dhaut Maidan

• Glacial wash plains are flat, broad areas formed by melting ice and depositing silt and debris.

• When the ice melts, water flows out from beneath the ice and deposits silt, gravel, sand, and clay on the land.

• This water collects glacial-alluvial deposits (gravel, sand, shale, etc.) and spreads them over wide, flat plains.

Drumlin

• Drumlins look like oval or elongated, smooth and curved hills.

• When a glacier melts, it carries a lot of rocks, sand and soil with it. This debris gets deposited under the ice and when the ice recedes, this debris gets deposited in a specific shape.

cliff 

• These are found on the seashores in the form of high, steep rocks, which are formed by the friction of waves. 

• The bottom of a sea cliff is a flat or gently sloping platform covered with debris brought by the waves.

Terraces

• When these platforms rise above the average height of the waves, they are called wave-eroded altars.

Caves

• The constant friction of the waves creates spaces at the base of the cliffs, leading to the formation of sea caves.

Stack

• The retreat of a cliff leaves some remnant rocks, which were previously part of the cliff, isolated on the shore, these are called sea stacks. 

• These too are gradually destroyed by the process of erosion.

Deposited landform

Beaches

• Beach sand is sand on the seashore that is mostly brought from land by rivers and streams or by wave erosion.

Bars

• Offshore, the ridge of sand and silt running parallel to the shore is called a bar. 

• These are found in the sea at some distance from the shore and are formed from sediments brought by waves and currents.

Barriers

• When the deposition of sand becomes so much that the barricade becomes visible above the sea level, it is called a barrier. 

• These structures are built at bay entrances or river mouths and protect coastal areas.

Spits

• When one end of a barrage is connected to a bay or land and the other end continues towards the sea, it is called a spit.

Pediment

• A gently sloping, broad, and flat rock surface found at the base of mountains or hills. 

• It is formed primarily due to erosion processes, where water and wind remove weathered material from the mountain face, leaving a flat surface.

Pediplain

• There is a wide, undulating plain that results from several pediments joining together. 

• As erosion continues, mountains are gradually eroded away, and their pediments join with the pediments of neighboring mountains to form a broad, flat plain called a pediplain.

Playa

• Playa is a type of landform found in deserts. It is mainly formed in areas that are surrounded by hills and mountains. 

• In these areas the drainage is mainly concentrated in the middle of the basin. Due to the deposition of sediments continuously brought from the edges of the basin a flat plain is formed in the middle of the basin. 

• When there is sufficient water available in this area, this flat plain turns into a shallow water lake.

Deflation Hollows

• When winds blow continuously in one direction in desert areas, they carry away rocks and unconsolidated soil particles. 

• Due to this process, shallow and wide depressions are formed on the surface, which are called drainage troughs.

Caves

• Due to the high velocity of winds, when flying dust and sand particles continuously hit the rocks, small pits or cavities are formed on the surface of the rocks. 

• These cavities become deeper and wider over time.

Mushroom Shell

• It is a type of rock formation in which the lower part of the rock is thin and the upper part is wide and round, giving it a mushroom shape.

Barchan

• These are crescent-shaped sand dunes with their arms pointing out in the direction of the wind. 

• Barkhans are formed when the wind direction is constant and the supply of sand is low.

Seif

• These are like barkhans, but have only one arm. 

• Seif dunes develop due to changes in wind direction, and can have high and long sides.

Parabolic Dunes

• These dunes are different from barkhans and their shape is parabolic. 

• Vegetation also contributes to their formation, which provides stability to the sandy surface.

Longitudinal Dunes

• These dunes are formed when the supply of sand is low and the wind direction is constant. 

• These are highly extended in length and reduced in height.

Transverse Dunes

• These dunes are formed at right angles to the direction of the wind. 

• They are formed when the wind direction is certain and the source of sand is at right angles to the wind direction.