Geomorphology Notes for UPSC

The surface of the Earth is never still. Mountains rise, rivers cut valleys, glaciers carve the land, winds make dunes and waves shape coastlines. The study of the origin, evolution and features of landforms is called geomorphology. It is the base of physical geography and a favourite area of the UPSC Civil Services Examination: Prelims asks about the types of rocks, weathering, features of rivers, glaciers, winds and coasts, and Mains asks about the processes behind landforms. This note explains the forces that shape the Earth, weathering and erosion, and the landforms made by different agents, in simple language, with tables for quick revision.

Forces That Shape the Earth

Two sets of forces act on the Earth. Endogenic (internal) forces come from within the Earth, such as the movement of plates, volcanoes, earthquakes, folding and faulting, and they build up the surface by creating mountains, plateaus and basins. Exogenic (external) forces act from outside, mainly through the atmosphere, water, ice and living things; they wear down the surface by weathering, erosion and deposition. The landscape we see is the result of a balance between the two: the endogenic forces create relief, and the exogenic forces level it down, a process called gradation.

Rocks and the Rock Cycle

Rocks are continuously changing from one form to another: this is the rock cycle. Igneous rocks are weathered into sediments, which form sedimentary rocks; heat and pressure change both into metamorphic rocks; and when these melt, new magma is formed. Fossil fuels such as coal and petroleum are found in sedimentary rocks.

Weathering

Weathering is the breaking down of rocks in place, without much movement. It prepares the material for erosion. There are three types.

• Physical (mechanical) weathering: breaking of rocks without changing their chemical composition. Examples: frost action (water freezes in cracks and expands), exfoliation (peeling of outer layers due to temperature changes, common in deserts), thermal expansion and contraction, and the growth of salt crystals.
• Chemical weathering: decomposition of rocks by chemical reactions. Examples: oxidation (iron rusts, giving reddish colour), carbonation (carbonic acid dissolves limestone), hydrolysis (feldspar changes into clay), solution (minerals like salt dissolve in water). It is most active in warm and humid regions.
• Biological weathering: by plants and animals, such as roots widening cracks, burrowing animals and acids from lichens.

The type of weathering depends on climate: physical weathering dominates in cold and dry regions, and chemical weathering in hot and wet regions. Mass wasting is the downhill movement of weathered material by gravity, as in landslides, rockfall, mudflows and soil creep. Weathering produces soil, so it is an important process for agriculture.

Erosion by Running Water

Running water is the most important agent of erosion in humid regions. In the upper course of a river, vertical erosion dominates, producing V-shaped valleys, gorges, canyons, rapids and waterfalls. A gorge is a deep, narrow valley with steep sides, and a canyon is a wide, deep valley, such as the Grand Canyon cut by the Colorado River. In the middle course, the river erodes sideways, forming meanders (loops), and when a meander is cut off, it forms an oxbow lake. In the lower course, deposition dominates, producing floodplains, levees (raised banks), braided channels and deltas where the river meets the sea. Deltas are named by their shapes: arcuate (Nile, Ganga), bird's foot (Mississippi) and estuarine (Narmada, Tapi). An alluvial fan forms where a mountain stream enters a plain, and a peneplain is the almost featureless plain formed in the final stage of erosion.

Cycle of Erosion

The American geographer W. M. Davis proposed the cycle of erosion with three stages: youth (the river is active, with steep V-shaped valleys and waterfalls), maturity (the valley widens, with a gentler slope and meanders), and old age (the land is worn down to a nearly flat peneplain). The idea is a simple model, and later geomorphologists have debated it, since uplift and erosion often happen at the same time.

Erosion by Groundwater: Karst Topography

In regions of limestone, groundwater dissolves rock and creates karst topography, named after the Karst region of Slovenia. Features include sinkholes (depressions), caves, underground streams, and, within caves, stalactites (hanging from the roof) and stalagmites (rising from the floor), which may join to form pillars. Examples in India are the Borra Caves (Andhra Pradesh), the Belum Caves and the Meghalaya caves.

Erosion by Glaciers

Glaciers are slow-moving rivers of ice, and they are powerful agents in cold regions. Erosional landforms include cirques (armchair-shaped hollows at the head of a valley), arêtes (sharp ridges), horns (pyramid-shaped peaks, like the Matterhorn), U-shaped valleys, hanging valleys and fjords (deep, narrow sea inlets in valleys flooded by the sea, found in Norway, New Zealand and Chile). Depositional landforms include moraines (rock debris carried by glaciers), drumlins (oval hills), eskers (long ridges formed by meltwater streams) and kettle lakes. Outwash plains are formed by meltwater in front of the glacier. In the Himalayas, glaciers like Gangotri and Siachen shape the valleys.

Erosion by Wind

Wind is active in dry regions where there is little vegetation. Deflation removes loose material and makes hollows (deflation hollows, like the Qattara Depression). Abrasion by wind-blown sand creates mushroom rocks (pedestal rocks), yardangs (streamlined ridges) and zeugens (table-like ridges). Wind deposition creates sand dunes: barchans (crescent-shaped dunes, with the horns pointing downwind) and seif (longitudinal) dunes. Very fine wind-blown dust forms loess deposits, which are fertile, as in northern China. The Thar desert has typical dune landscapes.

Coastal Landforms

Waves erode and deposit materials along the coast. Erosional features include cliffs, wave-cut platforms, caves, arches, stacks (isolated rock pillars) and stumps. Depositional features include beaches, spits (ridges attached to the land at one end), bars and lagoons (like Chilika Lake in Odisha, which is separated from the sea by a sand bar). A tombolo is a bar that connects an island to the mainland. Coastlines are classified as emergent (when land rises or sea level falls) and submergent (when land sinks or sea level rises), producing rias and fjords.

Landforms from Internal Forces

Folding produces anticlines (upfolds) and synclines (downfolds). Faulting produces rift valleys (a block of land sinks between two faults, as in the Narmada valley and the East African Rift) and horsts (uplifted blocks). Volcanoes produce cones, calderas (large crater-like depressions, such as Crater Lake) and lava plateaus (like the Deccan Traps). Earthquakes can raise or lower land and cause landslides.

Memory Tricks

Remember the order of weathering: P-C-B (Physical, Chemical, Biological). For glaciers, use "Cirque, Arete, Horn" for erosion and "Moraine, Drumlin, Esker" for deposition. For river stages, remember "Gorge, Meander, Delta" from source to mouth. For karst, "Stalactite hangs from the top (c for ceiling), stalagmite grows from the ground (g for ground)."

Landforms and Human Life

Landforms are not only a subject of study; they shape settlement, farming and economy. River plains and deltas such as the Ganga-Brahmaputra delta support very dense populations because of fertile alluvial soil and water. Loess plains give high farm yields. Fjords and sheltered bays give natural harbours. Limestone caves and karst areas attract tourism. Glacial valleys provide hydropower sites and tourism, while mountain slopes shape roads, railways and settlements. At the same time, landforms bring hazards: landslides in the Himalayas and the Western Ghats, floods in river plains, coastal erosion on beaches, and desertification at the edge of deserts. Understanding the processes helps in planning, for example by avoiding construction on unstable slopes and floodplains, and by protecting mangroves and dunes that act as natural barriers. This human angle is useful in Mains answers that ask about the significance of geomorphology for disaster management and development.

Quick Revision

• Endogenic forces build; exogenic forces wear down; rock types: igneous, sedimentary and metamorphic.
• Weathering: physical, chemical and biological; mass wasting is the movement of material under gravity.
• River features: gorge, meander, oxbow lake, levee, delta; karst: sinkholes, stalactites and stalagmites.
• Glacier features: cirque, arete, horn, U-shaped valley, fjord, moraine; wind features: barchan, loess.

Geomorphology becomes easy when you picture each landform. Draw simple sketches for each agent, revise the tables, and link examples from India and the world to make your answers more interesting.

Related Notes to Read Next

Continue your preparation with these related notes from the same subject:

• Minerals, Energy Resources and Industries of the World Notes
• Human Geography: World Population Notes for UPSC
• Plate Tectonics, Earthquakes and Volcanoes Notes for UPSC
• All World Geography notes

Frequently Asked Questions (FAQ)

What is geomorphology?

Geomorphology is the study of the origin, evolution and features of landforms on the Earth’s surface and the processes that shape them.

What is the difference between endogenic and exogenic forces?

Endogenic forces originate inside the Earth and build landforms, while exogenic forces act on the surface through weathering and erosion and wear them down.

What are the three types of rocks?

The three types of rocks are igneous, sedimentary and metamorphic rocks.

What is weathering?

Weathering is the breaking down and decay of rocks in place by physical, chemical and biological processes, without much transport.

What is the difference between weathering and erosion?

Weathering breaks down rocks in place, while erosion involves the removal and transport of the broken material by agents such as water, wind and ice.

What is an oxbow lake?

An oxbow lake is a crescent-shaped lake formed when a meander of a river is cut off from the main channel.

What is a delta?

A delta is a landform formed by the deposition of sediment at the mouth of a river where it meets the sea, such as the Ganga delta.

What is karst topography?

Karst topography is a landscape formed by the dissolving of limestone by groundwater, with features such as sinkholes, caves, stalactites and stalagmites.

What is a fjord?

A fjord is a deep, narrow sea inlet with steep sides, formed when a glacial valley is flooded by the sea, as in Norway.

What is a moraine?

A moraine is a ridge or deposit of rock and debris carried and deposited by a glacier.

What is a barchan?

A barchan is a crescent-shaped sand dune formed by wind, with its horns pointing in the direction of the wind.

What is loess?

Loess is a fine, wind-blown, fertile dust deposit, found for example in northern China.