EOSC 116 modA

• Mesozoic Earth


  Time of the Dinosaurs
• Lithosphere


  • Continental and oceanic crust and uppermost part of mantle
  • Fractured into a number of rigid sections
• Continental crust


  • Richer in materials with SiO2
• Oceanic crust


  • Richer in iron content
• Asthenosphere


  Upper mantle material that acts as relatively soft, lubricating layer over which crustal lithospheric plates move
• Mantle


  • Hot, viscous, taffy-like layer in continual motion with hot material rising from depth and cooler material sinking, creating convection currents that may help drive motion of lithospheric plates
• Outer core


  Liquid layer
• Inner core


  Solid layer with metallic composition
• Rocks


  Composed of minerals, an aggregate of minerals
• Mineral


  Naturally occurring, crystalline, inorganic substance with an ordered arrangement of atoms
• Granite


  • Composed of quartz, feldspar, biotite minerals
• Three Fold Rock Classification System

  • Igneous Rocks
  • Metamorphic Rock
  • Sedimentary Rock
• Igneous Rocks

  • Crystallize from melt to form interlocking crystals
  • Volcanic/extrusive rock melt cools at surface of the Earth
  • Plutonic intrusive rock melt cools inside of the Earth
  • Plutonic rocks exposed at surface via weathering erosion
  • Plutonic rocks cool slower, have more/larger crystals
  • Extrusive rocks cool rapidly and have smaller crystals
• Metamorphic Rock


  • Formed by alteration of pre-existing rocks via metamorphism
  • Process that transforms rocks involves heat/pressure and fluids percolating through subsurface
  • Can be compressed and flattened, new minerals can be generated more stable under new temperature/pressure
  • Pressure result of compressional tectonic forces when plates collide, can also generate heat
• Sedimentary Rock


  • Formed by physical erosion/weathering, chemical precipitation, biological precipitation
  • Physical erosion/weathering forms sandstone, siltstone, mudstone
  • Chemical precipitation forms evaporites when bodies of water evaporate
  • Biological precipitation produces coral reefs, sediments composed of shells, skeletons of microscopic plankton
  • Deposition of plant material in swamps forms peat and coal
  • Sediments transformed into rock through diagenesis/lithification
• Rock cycle


  1. Weathering

  2. Erosion

  3. Igneous rock

  4. Solidification

  5. Sediment

  6. Sedimentary rock

  7. Melting

  8. Mantle

  9. Metamorphic rock
• Age of the Earth

  4.54 billion years
• James Ussher (1581-1665) estimated the age of the Earth to be 6000 years BC based on adding up references in the Bible
• George Louis De Buffon (1707-1788) hypothesized the Earth solidified from a molten state and estimated it to be around 75,000 years old
• Stratigraphy


  Study of rock strata and the sequence of layers, provides information on geological history and relative ages of a region
• Sedimentary rock


  • Can be regarded as a book, each layer records details of Earth's environment at time of deposition, often contain fossils
• Relative Dating


  Technique relying on Laws of Stratigraphy to describe the way strata are laid over time, allows relative order of past events without determining absolute age
• Principles of Stratigraphy


  • Principle of Original Horizontality
  • Principle of Superposition
  • Principle of Lateral Continuity
• Relevant Structures in the Rocks

  • Tilted Strata
  • Folded Strata
  • Unconformities
  • Cross-cutting Relationships
  • Faulted Strata
  • Intruded Strata
• Biostratigraphy


  Using fossils to explore global geological histories
• Principle of Faunal Succession

  Fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances
• Best Fossils for Biostratigraphy

  • Short range, higher resolution
  • Common fossils
  • Live in environments where fossilization is likely
  • Present in many different environments
• Absolute Dating


  Timing the Earth, putting numbers on a geological scale
• Radiometric Dating


  Nucleus of radioactive atom spontaneously decaying to form atom of different element and energy, can be used to determine age of geological materials
• Half-life


  Time it takes for half of radioactive material to decay
• Radiometric dating is best used on closed material like crystals in igneous rock, limits include weathering, metamorphism, and clastic sedimentary rocks
• Volcanic ash can be used to date sediments, minerals that form in magma before erupting can also be used for dating
• Mesozoic Era


  • Cretaceous Period (144-65 Ma)
  • Jurassic Period (201-144 Ma)
  • Triassic Period (251-201 Ma)
• Current estimates indicate the Earth is 4.5 billion years old
• Pangea


  • Supercontinent, unbroken land from pole to pole, underwent cataclysmic change
• Erosion stripped away layers of rock, tectonic forces compressed and lifted land, carving the landscape
• Water is the strongest erosional force, cutting through solid rocks
• The Sun will eventually remove all life from the Earth's surface, and in about 5 billion years the Sun will run out of energy, collapse on itself, and engulf the inner planets
• Plate Tectonics


  Explains relationships between wide range of processes within the Earth, grew from the Theory of Continental Drift
• Theory of Continental Drift


  • Some land masses seem to fit together so well that it seemed unbelievable they were not once connected and subsequently drifted apart, based on observations by Alfred Wegener