Earth and Earth Systems – Quick Review

Factors That Make a Planet Habitable

  • Temperature: maintains liquid water; biochemical reactions function within a narrow thermal window.

  • Atmosphere: traps heat, blocks harmful radiation, supplies key gases (e.g., extN<em>2ext{N}<em>2, extCO</em>2ext{CO}</em>2).

  • Water: solvent, transport medium, thermal buffer, reactant.

  • Energy: steady external (Sun) + internal sources drive climate, cycles, and life processes.

  • Nutrients: provide elemental building blocks and energy sources for organisms.

Earth – Key Points

  • Third planet from the Sun; only known world with surface liquid water and life.

  • Size rank in Solar System: fifth largest.

Earth’s Systems (Closed System: exchanges energy, minimal matter loss)

Lithosphere / Geosphere

  • Solid crust + upper mantle; physical foundation for other spheres.

Hydrosphere

  • 70%70\% of surface covered by liquid water.

  • Only 3%3\% is fresh: 23\tfrac{2}{3} as ice, 13\tfrac{1}{3} in streams, lakes, groundwater.

  • Global water distribution: oceans 97.2%97.2\%, glaciers 2.15%2.15\%, groundwater/lakes/rivers/soil/atmosphere 0.65%0.65\%.

Atmosphere

  • Thin gaseous envelope: 78%78\% , $trace gases.

  • Redistributes heat via circulation; exchanges heat & moisture with hydrosphere (hydrologic cycle).

Major Layers (altitude)

  • Troposphere: 0––12\text{–}18\,\text{km};weather.</p></li><li><p>Stratosphere:; weather.</p></li><li><p>Stratosphere:11––50\,\text{km};ozone,jetaircraft.</p></li><li><p>Mesosphere:; ozone, jet aircraft.</p></li><li><p>Mesosphere:40––80\text{–}90\,\text{km};meteorsburn.</p></li><li><p>Thermosphere:; meteors burn.</p></li><li><p>Thermosphere:80\text{–}90––800\,\text{km};auroras,ISS.</p></li><li><p>Exosphere:; auroras, ISS.</p></li><li><p>Exosphere:800––3000\,\text{km}; transitions to space.

Biosphere

  • Sum of all ecosystems: soil to deep sea; interacts with all other spheres.

Sphere Interactions (Examples)

  • Volcanoes (geosphere) emit ash → nuclei for water droplets (hydrosphere) → increased rainfall → biosphere response; ash & gases influence atmosphere.

  • Acid rain: atmospheric \text{NO}x//\text{SO}x dissolve in rain (hydrosphere) → acidify soil (geosphere) & waters (hydrosphere) → harm organisms (biosphere).

  • Weathering/erosion (geosphere–hydrosphere) control ocean nutrient supply (biosphere).

  • Atmospheric chemistry & temperature regulate organismal viability.

  • Volcanic CO_2$$ + aerosols modify climate (atmosphere).

  • Rainfall/runoff sculpt land surface (geosphere) and transport materials (hydrosphere).