Keshu

Earth is the third planet from the Sun. It is the only known planet where life exists. It is a rocky planet with land, water, and air. Earth has mountains, oceans, rivers, deserts, forests, and many living things like humans, animals, and plants.

2. Shape and Size

• Earth is almost round but slightly flattened at the poles.

• Diameter is about 12,742 kilometers.

• Circumference is around 40,075 kilometers.

• It is the fifth largest planet in the solar system.

3. Structure of Earth (Inside Layers)

• Crust – The outer layer. Thin and solid. We live on this.

• Mantle – Below the crust. Made of hot, soft rock.

• Outer Core – Liquid metal, mainly iron and nickel.

• Inner Core – Solid metal, very hot and under high pressure.

4. Atmosphere

Earth is surrounded by a layer of gases called the atmosphere. It protects us from harmful rays and keeps the planet warm enough to live.

• Main gases: nitrogen (78 percent), oxygen (21 percent), and small amounts of other gases.

• The atmosphere has layers like the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

5. Water and Land

• About 70 percent of Earth is covered in water.

• 30 percent is land, including continents and islands.

• Water exists as oceans, lakes, rivers, glaciers, and underground.

6. Continents

There are seven continents:

• Asia

• Africa

• North America

• South America

• Antarctica

• Europe

• Australia

7. Earth’s Movements

• Rotation – Earth spins on its axis once every 24 hours. This causes day and night.

• Revolution – Earth orbits the Sun once every 365.25 days. This causes seasons.

• Earth is tilted at an angle of about 23.5 degrees, which affects how sunlight hits different parts.

8. Moon

Earth has one natural satellite – the Moon. It causes ocean tides and reflects sunlight. It takes about 27 days to orbit Earth.

9. Life on Earth

Earth supports millions of living species. Life needs air, water, sunlight, and the right temperature. No other known planet has all these things.

10. Natural Systems

• Water cycle – how water moves through evaporation, condensation, precipitation, and collection

• Carbon and nitrogen cycles – how elements move between the air, ground, and living things

• Tectonic plates – large pieces of Earth’s crust that move and cause earthquakes and volcanoes

11. Human Impact

• People have changed Earth through pollution, cutting down forests, and using too many resources

• This leads to problems like climate change, global warming, and loss of species

• Some people work to protect Earth by recycling, saving energy, and planting trees

12. Earth in the Solar System

• Third planet from the Sun

• Has gravity, which holds the Moon and atmosphere

• Protected from harmful space radiation by the magnetic field