GeoE/EnvE 153: Earth Engineering Spring 2025 Lecture 6: The Earth and It’s Systems

The Earth and Its Systems

• Civil, geological, and environmental engineers deal with all aspects of the Earth's systems:
  1. Lithosphere
  2. Hydrosphere
  3. Atmosphere
  4. Ecosphere
  5. Climate Change

Earth and the Solar System

• Universe is approximately 14 billion years old.
• Accretion of the Earth occurred about 4.6 billion years ago.
• The oldest rock exposure on Earth is about 3.5 - 4.0 billion years old.

A Chemically Differentiated Earth

• Crust:
  • Continental crust: granitic composition
  • Oceanic crust: basalt composition
• Mantle: iron-rich silicates
• Core: iron and nickel
• Lithosphere: crust and uppermost mantle

The Earth’s “Heat Engine”

• Convection is the dominant mechanism for redistributing thermal energy.
• Thermal convection causes rock/mineral mass to rise from the outer core.
• Conservation of mass implies that rock at the Earth's surface must be subducted into the interior.

Major Features of the Earth’s Surface

• Continental rocks:
  • Low density, older rocks (Na, K, and Ca silicates)
  • Concentrated by differentiation and recycling of the lithosphere
• Ocean basins:
  • Denser, younger rocks (Fe and Mg silicates)
  • Formed by mantle plumes that generate new oceanic lithosphere

Isostasy

• Isostasy is the state of gravitational equilibrium between the Earth's lithosphere and asthenosphere, where tectonic plates