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Looking for NCERT Class 11 Geography Fundamentals of Geography Chapter 5 Geomorphic Processes Notes? You’re in the right place! This blog gives you simple and clear notes that make it easy to understand the key concepts of this chapter. Whether you’re preparing for your exams or just want a quick revision, these notes will help you grasp the essential ideas without going through the entire textbook. Let’s dive in!
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Explore Notes of Class 11 Fundamentals of Geography
Introduction
The Earth’s surface is not still; it keeps changing. This happens because of natural processes called geomorphic processes that shape the landforms we see around us, like mountains, valleys, plateaus, and plains. These changes happen slowly over millions of years, but sometimes they can happen quickly too, like during earthquakes or volcanic eruptions.
Why is the Earth Uneven?
The Earth’s surface is uneven because its outer layer, called the crust, is constantly moving and changing. This movement happens both vertically (up and down) and horizontally (side to side). These changes are caused by forces inside the Earth, which push, pull, and break the crust, creating mountains, valleys, and plains. In addition to these internal forces, external forces such as wind, water, ice, and sunlight continuously act on the Earth’s surface, shaping it over time. The combined effect of these forces makes the Earth’s surface irregular and dynamic.
Also Read:
- NCERT Solutions and Notes for Class 7 Geography Chapter 7: Life in the Deserts (Free PDF)
- NCERT Class 7 Geography Chapter 3 ‘Our Changing Earth’: Notes and Solutions (Free PDF)
What are Geomorphic Processes?
Geomorphic processes are natural forces that constantly act upon the Earth’s surface to create and modify various landforms. These processes are responsible for forming features like mountains, valleys, rivers, and plains. They work over long periods and bring continuous change to the Earth’s crust. There are two main types of geomorphic processes:
- Endogenic processes: These are internal forces that originate from within the Earth. They tend to build up the surface by creating new landforms.
- Exogenic processes: These are external forces that operate on the Earth’s surface. They usually break down or wear away existing landforms.
Endogenic Processes (Internal Forces)
Endogenic processes come from inside the Earth and are responsible for the construction of new landforms. These processes include diastrophism, volcanism, and seismic activity.
1. Diastrophism
Diastrophism refers to the large-scale movement of the Earth’s crust, resulting in the formation of continents, mountains, and plateaus. It includes:
- Orogenic movements: These movements involve intense folding and faulting of rocks, which lead to the formation of mountain ranges such as the Himalayas.
- Epeirogenic movements: These are vertical movements of large landmasses, leading to the uplift or sinking of continents or plateaus without much folding.
2. Volcanism
Volcanism is the process through which molten rock (magma), gases, and ash are released from inside the Earth to the surface. It can result in:
- Formation of volcanoes.
- Creation of lava plateaus.
- Development of volcanic islands such as the Hawaiian Islands.
3. Earthquakes (Seismic Activity)
Earthquakes are sudden movements of the Earth’s crust caused by the release of energy from tectonic stress. They may cause:
- Cracks and fractures in the Earth’s surface.
- Uplift or subsidence of land.
- Triggering of landslides and tsunamis.
Exogenic Processes (External Forces)
Exogenic processes are forces that originate from outside the Earth and are primarily driven by climate elements like wind, water, temperature, and biological activity. These processes generally break down rocks and modify existing landforms. The major types of exogenic processes are:
- Weathering
- Mass Wasting (Mass Movements)
- Erosion and Deposition
1. Weathering
Weathering is the process of breaking down rocks at or near the Earth’s surface without moving them. It is caused by atmospheric elements such as temperature, water, wind, and biological activity. Types of Weathering:
1. Physical or Mechanical Weathering
This type breaks rocks into smaller fragments without changing their chemical composition. It occurs mainly in dry and cold climates. Major processes include:
- Frost action: Water enters cracks in rocks, freezes, expands, and causes the rock to break.
- Thermal expansion: Repeated heating and cooling cause rocks to expand and contract, eventually leading to cracks.
- Exfoliation: Outer layers of rocks peel off like onion skin due to temperature changes.
- Salt crystal growth: Salts in water crystallize in rock pores and cause the rock to break apart.
2. Chemical Weathering
Chemical weathering involves the decomposition of rocks through chemical changes. It is more effective in hot and humid regions. Key processes include:
- Solution: Minerals dissolve in water.
- Carbonation: Rainwater reacts with carbon dioxide to form weak carbonic acid, which dissolves rocks like limestone.
- Oxidation: Oxygen reacts with minerals, especially iron, forming rust.
- Hydration: Rocks absorb water, swell, and become weak.
- Reduction: Removal of oxygen from minerals under waterlogged conditions.
3. Biological Weathering
Biological weathering is caused by living organisms. It includes:
- Growth of plant roots in rock cracks, breaking the rocks apart.
- Burrowing animals like ants or rabbits loosen rocks and soil.
- Microorganisms produce acids that chemically break down rock minerals.
2. Mass Movements (Mass Wasting)
Mass movement refers to the downhill movement of soil and rock under the influence of gravity. It happens without the aid of flowing water, wind, or ice. This process is influenced by slope steepness, weathering, water content, and human activity. Types of Mass Movements:
- Slow Movements: Sometimes, soil moves downhill very slowly. One type is called soil creep, where soil slowly slides down a slope over a long time. Another type is solifluction, which happens when wet soil moves slowly over frozen ground. This usually happens in very cold places like the tundra.
- Rapid Movements: Other times, soil and rocks move quickly and suddenly. Landslides are when a large amount of soil and rocks quickly slide down a hill. Debris flows are fast floods made of water, mud, and rocks rushing down steep slopes. Slumps happen when a part of the land slides down in a curved shape, making step-like areas. Rockfalls occur when loose rocks fall straight down from cliffs or steep hills.
3. Erosion and Deposition by Natural Agents
Erosion is the process of removing weathered material, while deposition is the laying down of this material elsewhere. Various natural agents such as rivers, glaciers, wind, sea waves, and groundwater cause erosion and deposition, forming different landforms.
1. River (Fluvial) Action
Rivers are powerful agents of both erosion and deposition. They shape landscapes from mountains to plains.
| Erosional Landforms | Depositional Landforms |
| A river cuts down into the mountains and makes a deep valley shaped like the letter “V.” | Flat land next to a river that is made when the river floods and drops soil. It is good for farming. |
| When a river falls over a steep edge, it creates a waterfall with rushing water. | When a river slows down after coming out of a mountain, it drops sand and dirt in a fan shape. |
| A deep and narrow valley with steep sides made by the river cutting through rock over time. | At the river’s end, where it meets the sea, it drops a lot of soil and builds new land called a delta. |
2. Glacier (Glacial) Action
Glaciers are slow-moving masses of ice that erode, transport, and deposit rock materials.
| Erosional Landforms | Depositional Landforms |
| Bowl-shaped hollows found at the start of glacial valleys where ice collects. | Piles of rocks and dirt left behind as glaciers melt and move. |
| Wide valleys with flat bottoms carved by moving glaciers. | Smooth, long hills shaped by glaciers pushing and dropping sediment. |
| Sharp mountain peaks and narrow ridges created by glaciers cutting around mountains. | Long, winding ridges made of sand and gravel deposited by meltwater rivers under glaciers. |
| Flat areas covered with sediment spread out by melting glacier water. |
3. Wind (Aeolian) Action
Wind is a dominant geomorphic agent in arid and semi-arid regions. It erodes, transports, and deposits loose materials.
| Erosional Landforms | Depositional Landforms |
| Low areas formed when wind blows away loose sand and soil, leaving depressions. | Hills or mounds of sand built up by the wind blowing and piling it in one place. |
| Sharp, narrow ridges carved from rock by strong winds carrying sand. | Fine particles like silt and clay carried by wind over long distances and deposited as fertile soil. |
4. Sea Wave (Marine) Action
Sea waves continuously erode and deposit material along coastlines, changing their shape.
| Erosional Landforms | Depositional Landforms |
| Steep rock faces formed when waves constantly hit and wear away the coast. | Areas of sand, pebbles, and shells piled up along the shore by waves. |
| Flat areas found at the base of cliffs, created as waves erode the rock. | Long, narrow deposits of sand or pebbles that stretch into the sea. |
| Shallow water bodies near the coast, separated from the sea by sandbars. |
5. Groundwater Action
Groundwater causes erosion by dissolving soluble rocks such as limestone and gypsum, and it also contributes to deposition in caves.
| Erosional Landforms | Depositional Landforms |
| Round holes or depressions made when underground caves collapse. | Icicle-shaped formations hanging from cave ceilings made by mineral deposits. |
| Hollow spaces underground formed by water dissolving limestone rock. | Mineral formations rising up from cave floors, formed from dripping water. |
Soil Formation
Soil is formed by the breakdown of rocks and the accumulation of organic matter over time. This process is known as pedogenesis. The formation and quality of soil depend on several factors.
Factors Influencing Soil Formation:
- Parent rock: Determines the mineral content of the soil.
- Topography: Steep slopes have thinner soil; flat areas allow deeper soil.
- Climate: Temperature and rainfall control the rate of weathering.
- Biological activity: Plants, animals, and microbes contribute organic matter and help in weathering.
- Time: Longer periods allow more complete development of soil profiles.
Also Read:
- NCERT Solutions and Notes for Class 7 Geography Chapter 5: Water (Free PDF)
- NCERT Class 7 Geography Chapter 4 ‘Air’: Notes and Solutions (Free PDF)
Important Definition in NCERT Notes Class 11 Geography Chapter 5 Geomorphic Processes
This chapter explains how the Earth’s surface changes through different natural processes. It helps us understand how landforms like mountains, valleys, and plains are created and changed over time. Here are some important terms from the chapter, explained in an easy and simple way to help you remember them better.
1. Weathering: The breaking down of rocks into smaller pieces by natural forces like wind, water, and temperature changes.
2. Erosion: The process where weathered rock and soil are moved away by natural agents like water, wind, ice, or gravity.
3. Transportation: The movement of eroded materials (soil, rocks) from one place to another by water, wind, ice, or gravity.
4. Deposition: When the eroded materials settle down or are dropped in a new place after being transported.
5. Mass Wasting: The movement of soil and rocks down a slope due to gravity. It can be slow or fast.
6. Soil Creep: A very slow downhill movement of soil, happening over a long time.
7. Solifluction: Slow movement of waterlogged soil over frozen ground, common in cold places like the tundra.
8. Debris Flow: A rapid flow of water mixed with mud and rocks moving down steep slopes.
9. Slump: A curved sliding of a landmass down a slope, creating step-like formations.
10. Rockfall: When loose rocks fall freely from a cliff or steep slope.
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FAQs
Endogenic processes originate from inside the Earth and build up the landforms, such as mountain formation through diastrophism or volcanic eruptions. Exogenic processes occur on the Earth’s surface and mainly wear down or modify existing landforms through weathering, erosion, and deposition.
Weathering is the breaking down of rocks into smaller pieces without moving them, caused by factors like temperature, water, and biological activity. Erosion, on the other hand, is the removal and transportation of these weathered materials by agents such as water, wind, ice, or gravity.
Mass movements or mass wasting occur when soil and rocks move downhill due to gravity without the help of flowing water or wind. Types include slow movements like soil creep and solifluction, and rapid movements like landslides, debris flows, slumps, and rockfalls.
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