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:
- Lithosphere
- Hydrosphere
- Atmosphere
- Ecosphere
- 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