This MCQ module is based on: Spheres of the Earth — Lithosphere, Hydrosphere, Atmosphere and Biosphere
TOPIC 47 OF 50
Spheres of the Earth — Lithosphere, Hydrosphere, Atmosphere and Biosphere
🎓 Class 9
Science
CBSE
Theory
Ch 13 — Earth as a System: Energy, Matter, and Life
⏱ ~19 min
🌐 Language: [gtranslate]
🧠 AI-Powered MCQ Assessment
▲
📝 Worksheet / Assessment
▲
This assessment will be based on: Spheres of the Earth — Lithosphere, Hydrosphere, Atmosphere and Biosphere
Upload images, PDFs, or Word documents to include their content in assessment generation.
Introduction: One Planet, Many Connected Realms
Step outside on a clear morning in any Indian town. The ground beneath your feet is solid rock and soil. A river or pond holds liquid water. The wind that touches your cheek is a slice of the atmosphere. Birds, trees, insects and you yourself are alive — and the warm sunlight bathing it all comes from 150 million kilometres away. None of these things exists in isolation. Together they form a single, interconnected planetary machine. Scientists describe Earth as a system made of four overlapping spheres.
Big Idea: Earth is not a heap of separate things. It is one connected system in which rocks, water, air and living beings continuously exchange matter and energy.
13.1 The Four Spheres at a Glance
The four spheres are not stacked like layers of a cake — they overlap and mix. A drop of rain begins in the atmosphere, falls onto the geosphere, flows through a river of the hydrosphere, and is sipped by a deer of the biosphere. Each sphere has its own composition but constantly trades material with the others.
🌍 Spheres Tour — Click each sphere to recall what it contains L1 Remember
Click the geosphere, hydrosphere, atmosphere or biosphere circle to recall what each sphere holds and how it links to the others.
Click any sphere above (geosphere, hydrosphere, atmosphere, biosphere) to recall what it contains and where Indian examples fit in.
13.2 The Geosphere — Earth's Solid Body
The geosphere is everything solid about our planet — from a grain of sand on a Goa beach to the iron core thousands of kilometres below your feet. It is the stage on which the other spheres act.
Indian landforms in the geosphere
The Indian subcontinent shows the geosphere in spectacular variety. The towering Himalayas are young fold mountains still rising. The Deccan Plateau is a huge flat-topped highland built from ancient lava flows. The Thar Desert in Rajasthan is dry sand and rocky outcrops. The Gangetic Plain is fertile soil deposited by rivers over millions of years.
Inside the geosphere
Cut Earth open and you would see three main layers. The crust is the thin outermost shell (5–70 km thick) made of solid rock. Below it lies the mantle — a thick layer of hot, semi-solid rock that flows extremely slowly. At the centre is the core, made mostly of iron and nickel. Its outer part is liquid and its inner part is solid because of immense pressure. Heat from the core drives volcanoes, earthquakes and the slow drift of continents.
Soil — where geosphere meets life: Soil is more than crushed rock. It contains weathered minerals, decayed organic matter (humus), water, air and living organisms. Soil is the bridge that allows plants to grow and connects the geosphere to the biosphere.
13.3 The Hydrosphere — All the Waters of Earth
The hydrosphere covers about 71% of Earth's surface. Yet most of this water is salty and unusable for drinking or farming.
| Reservoir | Approx. share of total water | Notes |
|---|---|---|
| Oceans (salt water) | ~97% | The Indian Ocean borders our country to the south. |
| Glaciers and ice caps | ~2% | Himalayan glaciers feed rivers like the Ganga and Brahmaputra. |
| Groundwater | ~0.7% | Stored in pores between rocks; tapped by wells and tubewells. |
| Rivers and lakes | <0.01% | Tiny fraction yet vital for human use. |
India's perennial rivers — the Ganga, the Brahmaputra, the Yamuna, the Godavari, the Krishna and the Cauvery — together support more than a billion people. Lakes such as Dal Lake in Kashmir and Chilika Lagoon in Odisha host unique ecosystems. Beneath our feet, groundwater stored in aquifers is a hidden reservoir that we are using up faster than nature can replenish it.
13.4 The Atmosphere — Earth's Gaseous Blanket
The atmosphere is a mixture of gases held to the Earth by gravity. Although it extends hundreds of kilometres upward, almost all the air we breathe lies in the lowest few kilometres.
Composition of the air
| Gas | % by volume | Role |
|---|---|---|
| Nitrogen (N₂) | ~78% | Inert; needed by plants after fixation. |
| Oxygen (O₂) | ~21% | Used in respiration and burning. |
| Argon (Ar) | ~0.93% | Noble, unreactive. |
| Carbon dioxide (CO₂) | ~0.04% | Used in photosynthesis; traps heat. |
| Water vapour, others | variable | Drives weather and rainfall. |
Layers of the atmosphere
The troposphere is where almost all weather happens — clouds, rain, monsoons. Above it, the stratosphere contains the ozone layer that shields us from harmful ultraviolet rays. Higher still, the mesosphere burns up most meteors. The thermosphere holds the international space station and the dancing auroras of the polar skies.
13.5 The Biosphere — The Zone of Life
The biosphere is the zone where life is found. It overlaps all three other spheres — fish swim in the hydrosphere, birds fly through the atmosphere, earthworms burrow into the geosphere, and every one of us is part of the biosphere too.
India is one of just 17 megadiverse countries on the planet. From the snow leopards of Ladakh to the saltwater crocodiles of the Sundarbans, from the Western Ghats forests to the coral reefs of the Andaman Islands, the Indian biosphere is extraordinarily rich. Looking after it is a national responsibility.
13.6 The Sun — The Engine of It All
Without the Sun, Earth would be a frozen, lifeless rock. Sunlight powers almost every process in the four spheres:
- It heats the air and oceans, driving winds, ocean currents and the monsoons.
- It evaporates water from the seas, fuelling the water cycle and rainfall.
- It powers photosynthesis in plants, producing the oxygen we breathe and the food we eat.
- Only the deep heat of Earth's interior — driving volcanoes and earthquakes — comes from a different source: the geosphere itself.
Why this matters: Almost every form of energy we use, including the food on our plate and the fossil fuels in our vehicles, can be traced back to sunlight captured by living things. The Sun is the master clock of Earth's system.
13.7 How the Spheres Interact
The spheres are constantly trading matter and energy. Here are everyday examples from India:
- Atmosphere ↔ Hydrosphere: Sun-warmed seawater evaporates from the Arabian Sea, becomes the south-west monsoon, then falls as rain on Kerala.
- Hydrosphere ↔ Geosphere: The Ganga carves valleys through the Himalayas and lays down soil on the plains.
- Biosphere ↔ Atmosphere: A peepal tree absorbs CO₂ and releases O₂ during the day.
- Biosphere ↔ Geosphere: Earthworms loosen and enrich the soil for the next crop.
Activity 13.1 — Spotting Spheres in a Single SceneL4 Analyse
Predict first: In a photograph of a riverbank, how many spheres can you spot at the same time?
- Take a window seat in your home, school or a park. Spend two minutes looking carefully.
- List one thing you see that belongs to each sphere — geosphere, hydrosphere, atmosphere, biosphere.
- For any two of them, write a sentence describing how they affect each other.
- Mark with an arrow whether energy or matter is flowing.
Sample observation: Standing near a banyan tree after a shower, you might see — wet soil (geosphere), puddles of rainwater (hydrosphere), moist air with a breeze (atmosphere), and ants, birds and the tree itself (biosphere). The tree drinks water from the soil (biosphere ← hydrosphere ← geosphere) and releases water vapour into the air (biosphere → atmosphere). Almost every observation crosses two or more spheres, proving that Earth is a single linked system.
Competency-Based Questions L3 Apply
A geography teacher displays a satellite image of the Indian subcontinent during the south-west monsoon. The image shows white clouds over the Western Ghats, brown plains around the Thar, the green Gangetic basin, and the blue Bay of Bengal. The teacher asks students to interpret the picture using the four-sphere model.
1. Which sphere is represented by the white swirling clouds?
(c) Clouds are condensed water in air; they are part of the atmosphere — though they also belong to the hydrosphere as water droplets. Either way the visible feature in the air is atmospheric.
2. The brown patch of the Thar Desert mainly represents the:
(b) The exposed sandy surface is part of Earth's solid crust — the geosphere.
3. State two ways in which the Bay of Bengal (hydrosphere) influences the air above it (atmosphere) during summer.
It supplies water vapour through evaporation, fuelling rain clouds; and it moderates air temperature so the coast is cooler than the interior.
4. True or False: The biosphere is a separate layer that does not overlap with the other spheres.
False. The biosphere overlaps with all three — life is found in soil, water and air.
5. Fill in the blank: The chief outside source of energy that drives Earth's spheres is the __________.
Sun. Solar radiation powers winds, the water cycle, ocean currents and photosynthesis.
Assertion–Reason Questions L4 Analyse
Options: (A) Both A and R true, R explains A. (B) Both true, R does not explain A. (C) A true, R false. (D) A false, R true.
A: The hydrosphere is mostly fresh water available for drinking.
R: About 97% of Earth's water is in oceans and is salty.
(D) The assertion is wrong — most water is salty. The reason is correct and actually contradicts the assertion.
A: The ozone layer is in the stratosphere.
R: Ozone in this layer absorbs harmful ultraviolet rays from the Sun.
(B) Both statements are correct. The reason states what ozone does, but does not explain why it is located in the stratosphere — so it is a true but unrelated reason for the location.
A: Soil is part of the geosphere only.
R: Soil contains weathered rock, water, air and living organisms.
(D) The assertion is incorrect — soil overlaps the geosphere, hydrosphere, atmosphere and biosphere. The reason itself is correct and shows why the assertion fails.
AI Tutor
Science Class 9 — Exploration
Ready