Lecture 7: Plate Tectonics

Life As a Central Role in the Evolution of the Solar System

  • Early life forms
  • Early life used up some CO2CO_2 but not enough
  • There had to be another mechanism to remove the CO2CO_2
  • Organic matter deposited as sediment
  • Formation of limestone CaCO3=CaO+CO2\rightarrow CaCO_3 = CaO + CO_2
  • Long term storage (sequestration) of carbon dioxide in sediments and sedimentary rocks
  • Carbon cycle reached steady state ~3.8 GaGa
  • Without life, Earth would have a CO2CO_2 - rich atmosphere

What is Unique About Earth?

  • Special chemical composition of our atmosphere
  • Nitrogen and oxygen rich atmospheres are super rare
  • Existence of water in the 3 states near the surface
  • All planets have water, but we only have water in all 3 states (solid, liquid,vapor)
  • Eco sphere and biosphere
  • Region where life is possible (existence of life)
  • Dynamic nature of rock weathering
  • Soil: organic + inorganic components
  • Dynamic nature of the lithosphere
  • Plate tectonics


  • Earth has several characteristics that make it unique among known planets, and uniquely capable of supporting life
  • Early earth was a very different place that was hostile to all life but changed over time

Geological Cycles

  • Determine soil chemistry and replenish nutrients
  • Drive formation of mineral resources and fossil fuels
  • Influence development of landscapes and mountain ranges
  • Contribute to changes in atmospheric chemistry
  • Determine location, size, and shape of ocean basins
  • Control oceanic and atmospheric circulation and the distribution of climatic zones
  • Ultimately influences distribution of ecosystems and vegetation

The Rock Cycle

  • Igneous rock

Magma - molten liquid rock + gases + crystals

Lava - magma that reaches the surface

Igneous rock - forms when magma cools

  • Intrusive rocks (platonic rocks)
  • Magma cools and crystallizes slowly, well below the earth's surface
  • Extrusive (volcanic) rock
  • Magma is ejected from a volcano and cools and solidifies quickly at the surface

Sedimentary Rock

  • Particles transported by wind, water, ice
  • Forms near surface or surface environment

Lithification - formation of rock through the process of compaction and cementation

  • Fossils form only in sedimentary rocks

MetaMorphic Rock

  • Pre-existing rock, modified as a result to great heat or pressure
  • Temperature and pressure high enough to reshape crystals
  • Changes the appearance, physical

Earth is a Differentiated Planet

  • No homogeneous
  • Internal layering is defined by properties
  • Differences in composition

How Do We Know This?

  • It is actually a big challenge
  • Oddly we know more about the insides of other planets than ours

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