Concept

The Earth is an oblate spheroid. Latitudes (parallels) and longitudes (meridians) form a grid used to locate any point and to reckon time. The Earth rotates on its axis (causing day and night) and revolves around the Sun (causing seasons).

Longitude is directly linked to local time.

Key Points & Formulas

• Equator = 0° latitude; Prime Meridian = 0° longitude (through Greenwich).
• Earth rotates 15° of longitude per hour; the International Date Line is roughly 180°.
• Tropic of Cancer 23½°N, Tropic of Capricorn 23½°S.
• Indian Standard Time is based on 82½°E.

Worked Example

Q. If the local time at a place is ahead of Greenwich by 5 hours 30 minutes, find its longitude.

Earth turns 15° per hour ⇒ 1 hour = 15°, so 5.5 h = 82.5°.

Time is ahead of GMT ⇒ the place is east.

Longitude = 82½° E (this is India's standard meridian).

Practice MCQs

Q1. The Earth rotates through how many degrees of longitude in one hour?

(A) 15° (B) 30° (C) 1° (D) 360°

Answer: A. 360° in 24 hours = 15° per hour.

Q2. The Tropic of Cancer is located at

(A) 23½° N (B) 23½° S (C) 0° (D) 66½° N

Answer: A. The northern tropic lies at about 23½° North.

Concept

Rocks are natural aggregates of minerals, classified by how they form. The three families are igneous, sedimentary and metamorphic, linked by the rock cycle.

Each type has characteristic examples tested in the exam.

Key Points & Formulas

• Igneous: formed from cooled magma/lava (e.g., granite, basalt) — 'primary rocks'.
• Sedimentary: formed by deposition and compaction (e.g., sandstone, limestone); may contain fossils.
• Metamorphic: formed by heat/pressure on existing rocks (e.g., marble from limestone, slate from shale).
• The rock cycle continuously converts one type into another.

Worked Example

Q. Marble is formed from which rock and by what process?

Marble is a metamorphic rock.

It forms when limestone (a sedimentary rock) is subjected to heat and pressure.

Practice MCQs

Q1. Granite is an example of which type of rock?

(A) Igneous (B) Sedimentary (C) Metamorphic (D) Fossil

Answer: A. Granite forms from solidified magma — an igneous rock.

Q2. Fossils are most commonly found in

(A) Sedimentary rocks (B) Igneous rocks (C) Metamorphic rocks (D) Volcanic rocks

Answer: A. Layered deposition in sedimentary rocks preserves fossils.

Concept

Climate is the average weather of a region over a long period, shaped by latitude, altitude, distance from the sea and winds. Major climatic types range from equatorial to polar.

India's climate is dominated by the monsoon.

Key Points & Formulas

• Factors: latitude, altitude, distance from sea, ocean currents, winds.
• Equatorial: hot and wet all year; Desert: hot and dry.
• Mediterranean: dry summers, wet winters.
• India has a tropical monsoon climate (seasonal reversal of winds).

Worked Example

Q. Why are coastal areas cooler in summer and warmer in winter than inland areas?

The sea heats and cools more slowly than land (high specific heat).

It moderates nearby temperatures.

Hence coasts have a smaller temperature range than the interior.

Practice MCQs

Q1. India's climate is mainly of which type?

(A) Tropical monsoon (B) Mediterranean (C) Polar (D) Equatorial

Answer: A. Seasonal monsoon winds give India a tropical monsoon climate.

Q2. Which factor most lowers temperature as you go higher up a mountain?

(A) Altitude (B) Latitude (C) Longitude (D) Ocean current

Answer: A. Temperature falls with increasing altitude.

Concept

Agriculture and industry are the backbone of an economy. India's agriculture depends heavily on the monsoon, while industries are located near raw materials, power and markets.

Knowing crop–region and industry–location links is useful.

Key Points & Formulas

• Kharif crops (sown with the monsoon): rice, maize, cotton.
• Rabi crops (winter): wheat, gram, mustard.
• Black soil suits cotton; alluvial soil suits rice and wheat.
• Iron & steel industries locate near coal and iron ore (e.g., Jamshedpur).

Worked Example

Q. Why is black soil ideal for cotton cultivation?

Black (regur) soil is rich in clay and retains moisture well.

Cotton needs moisture-retentive soil and a warm climate.

Hence black soil is also called black cotton soil.

Practice MCQs

Q1. Wheat is mainly a

(A) Rabi crop (B) Kharif crop (C) Plantation crop (D) Zaid crop

Answer: A. Wheat is sown in winter (Rabi season).

Q2. The soil best suited for rice cultivation is

(A) Alluvial soil (B) Desert soil (C) Laterite soil (D) Black soil

Answer: A. Fertile, water-retentive alluvial soil suits rice.

Concept

International trade involves importing goods a country needs and exporting its surplus. India's trade pattern reflects its resources and industries.

Crude oil dominates India's import bill.

Key Points & Formulas

• Major imports: crude petroleum, gold, electronic goods, machinery.
• Major exports: refined petroleum products, gems & jewellery, textiles, software services.
• A trade deficit occurs when imports exceed exports.
• Ports handle the bulk of foreign trade by volume.

Worked Example

Q. What is meant by a trade deficit?

Compare the value of imports and exports.

When imports exceed exports, the difference is a trade deficit.

India typically runs a trade deficit, largely due to crude-oil imports.

Practice MCQs

Q1. The largest single item in India's import bill is usually

(A) Crude petroleum (B) Wheat (C) Tea (D) Cotton

Answer: A. India imports most of its crude oil, making it the top import.

Q2. A country has a trade surplus when

(A) Exports exceed imports (B) Imports exceed exports (C) Imports equal exports (D) It stops trading

Answer: A. Surplus means the value of exports is greater than imports.

Concept

Tides are the periodic rise and fall of sea level caused mainly by the gravitational pull of the Moon (and Sun). Ocean currents are large-scale movements of seawater that redistribute heat around the globe.

Spring and neap tides depend on the Sun–Moon alignment.

Key Points & Formulas

• Tides are caused chiefly by the Moon's gravitational pull.
• Spring tides (highest): Sun, Moon and Earth in line (full/new Moon).
• Neap tides (lowest): Sun and Moon at right angles (quarter Moon).
• Warm currents (e.g., Gulf Stream) raise coastal temperatures; cold currents lower them.

Worked Example

Q. When do spring tides occur?

Spring tides occur when the Sun, Moon and Earth are aligned.

This happens at full Moon and new Moon.

The combined pull produces the highest tides.

Practice MCQs

Q1. Tides are caused mainly by the gravitational pull of the

(A) Moon (B) Sun only (C) Earth (D) Stars

Answer: A. The Moon is the chief cause of tides; the Sun has a smaller effect.

Q2. The Gulf Stream is an example of a

(A) Warm ocean current (B) Cold ocean current (C) Tidal bore (D) Monsoon wind

Answer: A. The Gulf Stream is a warm current that warms north-west Europe.

Concept

The atmosphere is the envelope of gases around the Earth, divided into layers. Atmospheric pressure is the weight of air per unit area; differences in pressure drive winds.

Pressure decreases with altitude.

Key Points & Formulas

• Layers (bottom-up): troposphere, stratosphere, mesosphere, thermosphere.
• Weather occurs in the troposphere; the ozone layer is in the stratosphere.
• Atmospheric pressure decreases with height.
• Winds blow from high-pressure to low-pressure areas.

Worked Example

Q. In which atmospheric layer do almost all weather phenomena occur?

Weather (clouds, rain, storms) needs water vapour and convection.

These are concentrated in the lowest layer.

So weather occurs in the troposphere.

Practice MCQs

Q1. The ozone layer, which absorbs harmful UV rays, lies in the

(A) Stratosphere (B) Troposphere (C) Mesosphere (D) Thermosphere

Answer: A. Ozone is concentrated in the stratosphere.

Q2. As altitude increases, atmospheric pressure

(A) Decreases (B) Increases (C) Stays the same (D) Doubles

Answer: A. There is less air above at higher altitudes, so pressure falls.

Concept

India has diverse physical regions: the northern Himalayas, the northern plains, the peninsular plateau, the coastal plains and the islands. Each has distinct relief, rivers, climate and resources.

The Himalayas are the source of major north-Indian rivers.

Key Points & Formulas

• Physical divisions: Himalayas, Northern Plains, Peninsular Plateau, Coastal Plains, Islands.
• Himalayan rivers (Ganga, Brahmaputra) are perennial (snow-fed).
• Peninsular rivers (Godavari, Krishna) are rain-fed.
• The Deccan Plateau is rich in minerals.

Worked Example

Q. Why are Himalayan rivers perennial while peninsular rivers are seasonal?

Himalayan rivers are fed by both rainfall and melting snow/glaciers.

So they flow throughout the year (perennial).

Peninsular rivers depend only on rainfall, so they shrink in the dry season.

Practice MCQs

Q1. Which of these is a Himalayan (perennial) river?

(A) Ganga (B) Godavari (C) Krishna (D) Kaveri

Answer: A. The Ganga is snow-fed and perennial; the others are peninsular and rain-fed.

Q2. The Deccan Plateau is especially rich in

(A) Minerals (B) Glaciers (C) Mangroves (D) Coral reefs

Answer: A. The peninsular plateau holds large mineral reserves.

Concept

Transport networks — roads, railways, waterways and airways — move goods and people and support trade. India has one of the largest rail and road networks in the world.

Ports handle most of the country's international trade by volume.

Key Points & Formulas

• Railways are the principal mode of long-distance land transport.
• Major ports: Mumbai (JNPT), Chennai, Kolkata, Visakhapatnam, Kandla.
• National Highways connect major cities; the Golden Quadrilateral links the four metros.
• Inland waterways and coastal shipping are cheap for bulk goods.

Worked Example

Q. Why is sea transport preferred for bulky international cargo?

Ships can carry very large volumes at low cost per tonne.

Most of India's foreign trade by weight moves through ports.

Hence sea transport is preferred for bulk cargo.

Practice MCQs

Q1. The Golden Quadrilateral highway network connects

(A) Delhi, Mumbai, Chennai and Kolkata (B) Only southern cities (C) All state capitals (D) Hill stations

Answer: A. It links the four metro cities by expressways.

Q2. Most of India's foreign trade by volume is carried by

(A) Sea (ports) (B) Air (C) Road (D) Rail

Answer: A. Ports handle the bulk of international cargo by weight.