Atmosphere, Lithosphere and Hydrosphere

1. Atmosphere

1.1 Layers of the Atmosphere

1.2 Composition of the Atmosphere

• Nitrogen (78%): Most abundant gas
• Oxygen (21%): Essential for respiration
• Argon (0.93%): Inert gas
• Carbon Dioxide (0.04%): Greenhouse gas, vital for photosynthesis
• Other Gases (0.03%): Neon, helium, methane, water vapor, ozone, etc.

1.3 Important Terms and Concepts

• Greenhouse Effect: Trapping of heat by CO₂ and other gases
• Ozone Layer: Absorbs UV radiation, located in the stratosphere
• Ionosphere: Layer in thermosphere that reflects radio waves
• Auroras: Light displays caused by solar particles interacting with Earth’s magnetic field

1.4 Key Facts for Competitive Exams

• The troposphere is the layer where weather occurs.
• The stratosphere contains the ozone layer.
• The thermosphere is where auroras and ionosphere are located.
• Water vapor is a major component of the atmosphere and plays a key role in weather and climate.

2. Lithosphere

2.1 Components of the Lithosphere

• Crust: Outermost layer, composed of rocks and minerals
  • Continental Crust: Thicker (30-70 km), granitic, less dense
  • Oceanic Crust: Thinner (5-10 km), basaltic, denser
• Mantle: Beneath the crust, solid but can flow over long periods
  • Upper Mantle: Includes the asthenosphere, a semi-fluid layer
  • Lower Mantle: Solid, denser, under high pressure
• Core: Center of the Earth
  • Outer Core: Liquid, composed mostly of iron and nickel
  • Inner Core: Solid, due to extreme pressure, composed of iron

2.2 Important Terms and Concepts

• Plate Tectonics: Theory explaining the movement of Earth’s lithospheric plates
• Seismic Waves: Used to study the interior of the Earth
• Isostasy: Concept of balance between crust and mantle
• Volcanoes and Earthquakes: Result of tectonic activity

2.3 Key Facts for Competitive Exams

• The continental crust is thicker and less dense than the oceanic crust.
• The asthenosphere is a semi-fluid layer in the upper mantle.
• The outer core is liquid, while the inner core is solid.
• Plate tectonics explains the formation of mountains, volcanoes, and earthquakes.

3. Hydrosphere

3.1 Water Bodies

3.2 Water Cycle

• Evaporation: Water from oceans, lakes, and land turns into vapor
• Condensation: Vapor cools and forms clouds
• Precipitation: Water falls as rain, snow, sleet, or hail
• Runoff: Water flows over land into rivers and oceans
• Infiltration: Water seeps into the ground to become groundwater

3.3 Important Terms and Concepts

• Hydrological Cycle: Continuous movement of water on, above, and below Earth’s surface
• Freshwater vs. Saltwater: Freshwater is less than 3% of Earth’s total water
• Aquifers: Underground layers of water-bearing permeable rock
• Transpiration: Evaporation of water from plants

3.4 Key Facts for Competitive Exams

• Oceans contain 97% of Earth’s water.
• Glaciers store ~68% of Earth’s freshwater.
• The hydrological cycle is crucial for climate regulation and ecosystem sustainability.
• Groundwater is a major source of freshwater for many regions.
• Transpiration contributes to the water cycle and influences local climates.