Exterior of the Earth
a. Lithosphere (Solid Layer)
- Location: Outermost solid shell of the Earth.
- Coverage: ~30% of Earth’s surface
- Composition: Rocks, minerals, and soil.
- Density: 2.5 to 3.0 g/cc (outer crust); ~5.5 g/cc (average for entire Earth).
Key Features:
- Visible landmass forms 1/4th of Earth’s surface, mostly in the Northern Hemisphere.
- Composed of tectonic plates floating over the semi-molten asthenosphere.
- Thickness: 10 to 20 miles (~16 to 32 km).
- Supports life—both plant, and animal
b. Hydrosphere (Liquid Layer)
- Location: All water bodies covering Earth’s surface.
- Coverage: ~70% of Earth’s surface.
- Density: ~1.026 g/cc (seawater).
- Salinity: ~3.5% dissolved salts (primarily sodium chloride).
Key Features:
- Includes oceans, seas, lakes, rivers, and underground water.
- Seawater density varies based on:
- River inflows → Lower density.
- High evaporation zones → Higher density.
c. Atmosphere (Gaseous Layer)
- Location: Extends ~320 km above the surface.
Composition:
- 78% Nitrogen (N₂)
- 21% Oxygen (O₂)
- 93% Argon (Ar)
- 04% Carbon Dioxide (CO₂)
- Trace gases: Neon, Helium, Methane, Krypton, Hydrogen, & water vapor.
Key Features:
- Troposphere: Weather phenomena occur here.
- Stratosphere: Ozone layer present.
- Mesosphere: Meteors burn here.
- Thermosphere: Auroras occur here
Composition of Earth’s Crust
- Oxygen (O) – ~46.6%
- Silicon (Si) – ~27.7%
- Aluminum (Al) – ~8.1%
- Iron (Fe) – ~5.0%
- Calcium (Ca) – ~3.6%
- Sodium (Na) – ~2.8%
- Potassium (K) – ~2.6%
- Magnesium (Mg) – ~2.1%