Shaping of the Earth Surface Class 9 PPT & Notes PDF | USP

Class 9 Social Science Chapter 2 – Shaping of the Earth's Surface

Mountains, valleys, plains, and coastlines all look permanent, but the Earth's surface is constantly being built up and worn down by powerful natural forces. In this chapter, "Shaping of the Earth's Surface," Class 9 CBSE Social Science (Geography) students learn about the internal and external forces that shape landforms, the theory of plate tectonics, and how rivers, wind, glaciers and coasts carve the land over time. This free PPT and notes download covers the complete NCERT 2026–27 syllabus in a simple, exam-focused format so you can revise quickly before tests.

Internal (Endogenic) Forces

Internal forces originate from within the Earth and are responsible for building up the land, creating mountains, plateaus, and landmasses.

• Earthquakes: Sudden shaking of the Earth's crust caused by the release of energy along faults.
• Volcanoes: Openings in the Earth's crust through which molten rock (magma), ash, and gases escape, often forming new landforms.
• Folding: Occurs when rock layers are compressed and bent, usually forming mountain ranges like the Himalayas.
• Faulting: Occurs when rocks break and shift along a fracture, often causing block mountains and rift valleys.

External (Exogenic) Forces

External forces act on the Earth's surface from outside and are responsible for wearing down and levelling the land through three continuous processes.

• Weathering: The breaking down of rocks in place due to temperature changes, water, wind, or living organisms, without any movement of material.
• Erosion: The process by which weathered material (soil and rock fragments) is picked up and transported by agents like rivers, wind, glaciers, and waves.
• Deposition: The process by which eroded material is dropped or settled at a new location, forming new landforms such as plains and deltas.

Plate Tectonics

According to the theory of plate tectonics, the Earth's crust is broken into several large and small plates that float on the semi-molten mantle below and are constantly moving, though very slowly. The movement and interaction of these plates at their boundaries is responsible for most of the major landforms and natural events on Earth, including earthquakes, volcanoes, and mountain formation.

Landforms Created by Rivers

Rivers are one of the most powerful agents of erosion and deposition, and they create distinctive landforms in each stage of their journey from source to sea.

• Upper Course: Steep gradient with strong erosional activity, forming V-shaped valleys and waterfalls where the river flows over hard rock.
• Middle Course: Gentler gradient where the river begins depositing material, forming winding bends called meanders.
• Lower Course: Very gentle slope near the sea, where the river deposits large amounts of sediment, forming flat floodplains and triangular deltas at the mouth.

Landforms by Wind, Glaciers, Coasts and Groundwater

Besides rivers, several other agents shape the Earth's surface in specific regions. Wind action in deserts creates landforms such as sand dunes and mushroom rocks. Glaciers carve out U-shaped valleys and deposit material as moraines in cold mountainous regions. Coastal waves erode cliffs and build beaches, while groundwater dissolves limestone to form caves and stalactites in karst regions.

Types of Plate Boundaries

Real-Life Applications

Understanding the forces that shape the Earth's surface helps in disaster preparedness, since regions near plate boundaries such as the Himalayas and the Pacific Ring of Fire are more prone to earthquakes and volcanic eruptions. City planners and engineers use this knowledge to design earthquake-resistant buildings in high-risk zones. Farmers and geographers rely on the study of river landforms to understand fertile floodplains and predict flooding, while knowledge of weathering and erosion is essential in soil conservation, mining, and construction projects.

Frequently Asked Questions

Q1. What is the difference between internal and external forces?
Internal forces originate within the Earth and build up landforms such as mountains and volcanoes, while external forces act from outside and wear down the land through weathering, erosion, and deposition.

Q2. What is the difference between weathering and erosion?
Weathering is the breaking down of rocks in place without any movement, while erosion involves the transportation of the broken material by agents like water, wind, or ice.

Q3. What landforms does a river create in its upper course?
In its upper course, a river creates V-shaped valleys and waterfalls due to strong erosional activity on a steep gradient.

Q4. What is plate tectonics?
Plate tectonics is the theory that the Earth's crust is divided into several plates that move slowly over the mantle, and their movement at boundaries causes earthquakes, volcanoes, and mountain building.

Q5. What is a delta and where is it formed?
A delta is a triangular landform made of sediment deposited by a river where it meets the sea or a lake, formed in the lower course of the river.

What's Included in This Free Download

• 51-slide PPT covering the complete chapter with diagrams and real-life examples
• Complete notes based on the new NCERT 2026–27 syllabus
• Practice worksheet with important questions

Prepared by Sumeet Sahu, Unique Study Point, Indore. Free for all Class 9 CBSE students.