Chapter - 7
Land forms and their development
️ Geo-shapes :-
The factors of erosion play a major role in the formation of the Earth's surface. Rivers, winds, glaciers and waves etc. come in these factors of erosion.
They break the rocks of the ground floor. They carry the sediments received from them and deposit it elsewhere. By these processes, many types of landforms are formed on the surface, we can divide all these landforms into shapes made of erosion and deposition.
️ Geomorphology :-
Geomorphology is the study of the history of the earth's surface, in which its shape, materials and processes from which this surface is made, are studied.
️ Landforms :-
- Volcano
- canyon
- Mountain
- Field
- island
- Lake
- Waterfall
- valley
️ eroded Ruthalroop :-
The figures formed by the rivers are the figures formed by erosion, v shaped canyon, gorge, canyon, waterfall and eroded fissure .
Deposited landforms: -
River Vedikas, Gokhur Lake, Gumphit River come under the figures made of deposition .
️ River | Flowing water:
Different stages of landform development formed by the river :-
- Youth (in hilly region)
- Adulthood (in plains)
- Old age (in delta regions)
️ Youth :-
This stage of rivers is found in mountainous areas and the number of rivers in this stage is very less.
These rivers form V-shaped valleys in which flood plains are absent or narrow flood plains are found along the main river.
In this, the water divides are very wide, in which there are swamps and lakes.
️ Adulthood :-
This state of rivers is found in the plains. In this stage, the amount of water in the rivers is high and many tributaries also come and get mixed in it.
River valleys are V-shaped but deep. In this stage the river is wide and wide, hence wide floodplains are found.
In which the river flows within the valley becoming a whirlpool.
️ Old age :-
This stage is found in delta regions and in this stage, small tributaries get reduced. And the slope gradually slows down and the rivers flow freely in the wide flood plains and form river estuaries, natural embankments, Gaukhur lakes etc.
️ Eroded Landforms ️
️ Valleys :-
The valleys start with small streams, these small streams gradually develop into long and wide tubules and these tubes gradually become deeper and broader and longer and take the form of valleys.
These valleys are divided on the basis of length, width and shape – V-shaped valley, gorge, canyon.
️ Guard :-
The gorge is a deep narrow valley with sharp slopes on both sides.
The width of the guard is almost equal in its bottom and upper part.
The gorge is formed in hard rocky areas.
️ Canyon :-
The banks of the canyon are also steep slopes and are as deep as the gorge itself.
The upper part of the canyon is wider than the bottom.
Canyons are often formed by horizontal stratification of sedimentary rocks.
️ Water Socket :-
Small rocky pieces by getting stuck in the river bed make a trough by rotating round and round at the same place, it is called water trough.
️ Depressed pool (PlungePool) :-
A deep and large water well is formed at the bottom of the waterfall, which is formed by the fall of the water from the height and the circular rotation of the boulders in it. Such wide and deep pools at the bottom of waterfalls are called Plunge Pools, these pools are helpful in deepening the valleys.
️ River Vedas :-
River altars are the bedrock of early floodplains or ancient river valleys. These altars are formed by vertical erosion in the flood plains. There may be several altars at different heights showing the initial river water level.
️ Types of river altars :-
There are two types of river Vedas.
- paired altars
- unpaired alveoli
️ Paired altars :-
If the river altars are of equal height on both sides of the river then they are called paired altars.
️ Unpaired Vedas :-
When the altars are found only on one bank or bank of the river and not on the other or there is a difference in their height on the banks, then such altars are called unpaired altars.
️ Reasons for the origin of river Vedas :-
River Vedikas arise due to the following reasons:-
- Decreased water flow.
- Change in water area due to climate change.
- Earthquake due to tectonic causes.
- If the rivers are near the coast, then the change in sea level.
️ Waterfall :-
When the water of the river passes through such a hard rock, which it cannot cut, and next comes a soft rock which it cuts easily, then gradually there is a difference in the river bed and its water from top to bottom. It falls like a waterfall.
️ Kshiprika :-
When hard and soft rocks come in sequence on the river bed, then the river starts flowing on it making a ladder-like shape, in this process many small waterfalls are formed, they are called Kshiprikas.
✴️ Deposited landmarks
️ Alluvial feathers :-
When the river comes down from the mountainous areas, its flow slows down and it collects the pebbles that came with it in the shape of a triangular fan. This is called alluvial feather.
️ Delta :-
The rivers, while falling into the sea, flow very slowly due to high depression and slow slope and deposit the depression in a triangular shape which is called delta.
️ Flood plains :-
Just as valleys are formed by erosion, in the same way, flood plains are formed by deposition.
Flood plains are the main form of river deposition. Fine materials like sand, clay particles, pebbles, stones, get deposited in the low lying areas around the river and thus water spreads on the banks every year due to floods. They get deposited in that place and these are called flood plains.
️ River Vispar :-
S shaped curve in the river course is called river visorp. When the river flows slowly in the plains, it makes such bends due to excessive load. Erosion on the outer bank of the river and deposition on the inner bank increases the size of the curve. Which is separated from the river over time, which is called Gokhur Lake.
️ Gumphit River :-
The speed of flow slows down in the lower valley of the river and the river starts depositing its sediments. Due to this the river divides into many branches. These branches are separated from each other by a wall made of sand. Such a river divided into branches is called Gumphit River.
( Groundwater ) :-
The horizontal and vertical flow of water flowing in a horizontal state through the joints, holes, of the rocks under the water surface is the reason for the erosion of the rocks. Lime-rich rocks form many landforms by chemical reaction in wet areas where rainfall is high.
️ Erosion landforms formed by underground water / ground water :-
Slurry stoma :-
These are funnel shaped troughs which are circular from above. Their depth varies from half a meter to 30 meters or more.
Merger Stoma:-
These are attached at some depth to the bottom of the slurry. They are formed by molten action at the bottom of limestone rocks.
Lapis :-
Gradually, most of the selected rocks turn into gorges and trenches and very irregular thin and sharp ridges are left in the whole area, which are called lapiges. They are formed by dissolving processes in the joints of rocks.
Deposited land forms formed by ground water / ground water: -
Stalactite :-
It is the topography formed by the deposition process in the lime regions. Lime mixed water drips from the roof of the caves. Some part of the dripping droplets are left hanging in the ceiling. Its water evaporates as steam and lime remains stuck in the roof. The shape of such hanging pillars is called stalactite.
Stalagmite :-
When lime mixed water falls below the canopy of the caverns, the water evaporates but the lime freezes on the same surface. In this way a pillar stands on the ground of the caves. Which is called stalagmite.
Pillar :-
Both stalactites and stalagmites of different thicknesses grow and join together, which is called Kandara Pillar or Lime Pillar.
️ Glacier :-
Glacier The snow flow on the earth in the form of a thick layer or the snow mass flowing in the form of linear flow from mountain slopes to valleys is called.
️ How many types of glaciers are there?
It is of two types :-
Continental Glaciers or Giripad Glaciers: - These are the glaciers which are spread over a large flat area in the form of a layer of ice.
Mountain or Valley Glaciers: - These are the glaciers which flow in the valleys on the mountain slopes.
Features of Glacier :-
The flow of glacier is much slower than flowing water.
Glaciers can flow from a few centimeters to a few meters per day.
Glaciers are mainly caused by the force of gravity.
️ Erosion site created by glacier :-
Sark : - In the upper part of the glacier, there is erosion on the bottom, in which troughs with steep edges are formed which are called sarks.
Tarn Lake:- The water gets filled in the sark due to the melting of glaciers. Which is called Tarn Lake.
Shringa: When two sarks meet in opposite directions, then a shape like a pointed peak is formed. which is called a horn.
Deposits made by glaciers: -
Drumlin :- A pile of sand and gravel collected by glacier is called drumlin.
Sheep Rock: - A heap of sand, gravel and rocks whose slope is slow on one side and sharp on the other.
️ Fiord :-
Very deep glacial depressions in which sea water is filled and which are on the sea coastline are called fjords.
(Monadanox): -
The dividers in the middle of the drainage basin lower until they are completely flat and eventually a slow relief is formed in which the remains of obstructed rocks are visible somewhere, it is called a moninoak.
Enselberg: -
As a result of erosion, standing landforms in the form of remnants of mountains in desert areas are called Iselbergs.
️ Erosion and deposition by winds and description of landforms formed from them :-
Erosion and deposition by winds depend on the amount of particles carried by it.
It is more in deserts and semi-arid areas where there is a barrier free area for a long time.
The wind cannot lift the coarse sand particles to a high height. Therefore, the erosion work is confined to a small height.
The wind rubs the rocks present like sand.
Transport of eroded material depends on the speed of wind.
Based on these principles, the following figures are formed in dry desert and semi-arid regions:
Beehive Shell: - When strong winds cut a rock by the effluent particles, then the top shell becomes like an umbrella.
Barkhan:- The sand particles that the winds carry with them, when the speed becomes the object, they gather in one place and take the form of a crescent moon. Their slope is slow on one side and sharp on the other. These dunes keep moving forward.
