1. Which one of the following scholars suggested the Earth’s origin from gases and dust particles?
2. The Nebular hypothesis of origin of Earth was given by
3. Who among the following modified the Nebular theory of Laplace during mid-19th century?
4. In terms of its size, the rank of Earth among the planets is
5. The diameter of Earth is approximately
6. Which of the following correctly describes the shape of Earth?
7. Earth has ……… types of motion.
8. The Earth rotates on its axis in which direction?
9. The plane formed by the axis and orbit is known as the ……… .
10. The movement of the Earth on its axis is called as ……… .
11. How many degrees does the Earth rotate about its own axis in one hour?
12. The Coriolis effect is the result of
13. The scientist who first discovered that Earth revolves around the sun was
14. At which average speed does the Earth revolve around the Sun?
15. The Earth completes one rotation on its axis in
16. The movement of the Earth around the Sun in a fixed path or orbit is called
17. In completing one revolution of the Sun, Earth takes approximately
18. What is the approximate mean velocity with which the Earth moves around the Sun in its orbit?
The Earth
Earth, the third planet from the Sun, is unique in the solar system due to its abundant water, atmosphere, and ability to support life. For millions of years, it has nurtured ecosystems, climatic patterns, and geological phenomena, making it a crucial subject for various competitive exams.
1. Basic Facts about Earth
- Position in the Solar System: Earth is the third planet from the Sun, after Mercury and Venus.
- Shape: Earth is an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator due to its rotation.
- Size: With a diameter of about 12,742 km, Earth ranks as the fifth-largest planet in the solar system.
- Age: Estimated to be around 4.5 billion years old.
2. Structure of the Earth
Earth is made up of several layers, each with unique characteristics:
- Crust: The outermost solid layer, consisting of continents and ocean basins. It varies in thickness, being thinner beneath oceans and thicker beneath continents.
- Mantle: A thick, semi-solid layer below the crust, making up about 84% of Earth’s volume.
- Core: Divided into an outer core (liquid) and an inner core (solid), primarily made of iron and nickel. The core is responsible for Earth’s magnetic field.
3. Earth’s Atmosphere
Earth’s atmosphere is a blanket of gases crucial for sustaining life. It consists of five main layers:
- Troposphere: The lowest layer, where weather occurs.
- Stratosphere: Contains the ozone layer, which absorbs harmful UV rays.
- Mesosphere: Known for burning up meteors that enter Earth’s atmosphere.
- Thermosphere: High temperatures occur here; it’s where the auroras form.
- Exosphere: The outermost layer, gradually merging into space.
Key Composition: Nitrogen (78%), Oxygen (21%), and trace amounts of other gases, including carbon dioxide and argon.
4. Earth’s Movements
- Rotation: Earth rotates on its axis from west to east, taking approximately 24 hours, which creates day and night.
- Revolution: Earth revolves around the Sun in an elliptical orbit, taking 365.25 days to complete one orbit, which defines a year.
- Tilt of Axis: Earth’s 23.5° tilt is responsible for the changing seasons.
5. Earth’s Magnetic Field
Earth’s magnetic field, generated by its liquid outer core, extends into space and protects the planet from harmful solar radiation. This magnetic shield also causes the beautiful auroras near the polar regions.
6. Water on Earth
- Hydrosphere: Earth’s water cover, including oceans, seas, rivers, and lakes, covers about 71% of its surface.
- Importance of Water: Water is essential for all life forms, regulating temperature, and shaping landscapes through erosion and deposition.
- Ocean Currents: Currents like the Gulf Stream and the Humboldt Current significantly influence regional climates and marine biodiversity.
7. Continental Drift and Plate Tectonics
- Theory of Continental Drift: Proposed by Alfred Wegener, this theory suggests that continents were once part of a supercontinent, Pangaea, which gradually split apart.
- Plate Tectonics: Earth’s crust is divided into tectonic plates that float on the semi-fluid mantle, leading to seismic activity, mountain formation, and volcanic eruptions.
8. Climate Zones and Biomes
- Climate Zones: Earth has three main climate zones – tropical, temperate, and polar – primarily determined by latitude.
- Biomes: Distinct ecosystems (like forests, deserts, and tundras) are shaped by climate, soil, and vegetation patterns.
9. Important Natural Phenomena
- Earthquakes: Caused by the sudden release of energy in Earth’s crust due to tectonic movement. The point directly above the earthquake’s origin on the surface is called the epicenter.
- Volcanoes: Openings in Earth’s crust that allow magma, ash, and gases to escape from below.
- Cyclones: Large-scale air masses that rotate around a low-pressure center, mainly affecting tropical and subtropical regions.
10. Environmental Challenges
- Climate Change: Due to increased greenhouse gases, Earth’s temperature is rising, affecting ecosystems and leading to phenomena like melting glaciers and rising sea levels.
- Deforestation and Pollution: Major threats to biodiversity, contributing to habitat loss, air and water pollution, and soil degradation.
- Conservation Efforts: Initiatives like the Paris Agreement, reforestation, and pollution control aim to protect Earth’s resources for future generations.
Quick Recap for Exams
- Earth is unique due to its atmosphere, water, and life-sustaining capabilities.
- Layers of Earth include the crust, mantle, and core.
- The atmosphere protects life and includes layers like the troposphere and stratosphere.
- Movements of Earth, such as rotation and revolution, cause day, night, and seasons.
- Key phenomena include earthquakes, volcanoes, and cyclones.
- Climate zones, biomes, and environmental issues are essential topics for understanding Earth’s ecosystems and conservation efforts.