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Intro to Physical Geology (EAR 110)

Intro to Physical Geology (EAR 110). What is Geology? … the study of Earth . Two Divisions: Physical geology  minerals, rocks, Earth processes Historical geology  origin & evolution of continents, oceans, atmosphere, & life. interdisciplinary (astronomy, biology, physics, & chemistry).

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Intro to Physical Geology (EAR 110)

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  1. Intro to Physical Geology(EAR 110)

  2. What is Geology?… the study of Earth Two Divisions: • Physical geology minerals, rocks, Earth processes • Historical geology origin & evolution of continents, oceans, atmosphere, & life interdisciplinary (astronomy, biology, physics, & chemistry)

  3. Why is Geology Important to You? • Minerals have practical daily uses. (toothpaste, vitamins, drink cans, cosmetics, salt, pencil “lead”, jewelry, currency, ceramics, paints, fertilizers, lubricants, abrasives, etc.) • Informed decisions are essential. • (i.e., mineral rights, safety of water supply, • stream flooding, community planning boards, • communication to legislators enacting • environmental regulations)

  4. Knowledge of geologic hazards lessens the severity of their impact. • Standard of living is dependent on the use of geologic materials. (i.e., Overuse of resources adversely affects balance of nature, culture, & environment.) Sustainable development insures future generations sufficient natural resources to maintain standard of living for a larger population.

  5. A complex, dynamic system SYSTEMS:atmosphere, biosphere, hydrosphere,lithosphere, mantle, & core.

  6. 3 Physical Environments: 1.Solid Earth– core, mantle, & crust 2.Hydrosphere– dynamic mass of H2O The Water Cycle --evaporation from oceans into the atmosphere -- precipitation onto land -- water flows back into the oceans 3. Atmosphere – gaseous envelope around Earth (interaction b/w surface & atm.  WEATHER)

  7. Characteristics of Earth’s Core • composed of Fe (minor Ni & other heavy elements) • inner core: solid, Fe-rich sphere • outer core: molten metallic layer They’re compositionally similar. Magnetic field provided by circulation of the molten outer core

  8. Characteristics of Earth’s Mantle • 82% of Earth  ~2900km thick • located below the crust • behaves like a solid when EQs pass thru it, but can flow slowly (plastic) Divided into regions: Upper:(Asthenosphere) crust thru upper mantle (660km into Earth) Lower:(Mesosphere) from a depth of 660km to the outer core

  9. Characteristics of Earth’s Crust LITHOSPHERE rigid, solid Thickness: Average = 15 km 3 km (~2mi) at ocean ridges 70 km (40 mi) in ancient mtn belts Oceanic: Continental: Basalt/Gabbro Andesite/Granodiorite more dense (3 g/cm3) less dense (2.7 g/cm3) younger (180 my to pres) older (up to 3.8 by)

  10. Formulation of Theories • theory speculative explanation; wild guess • theory (scientific)  coherent explanation supported by large body of evidence; validity of explanation testable by experiment How are theories born? The Scientific Method Refinement occurs by further testing.

  11. The Scientific Method 1.Collection of Data  gather scientific facts thru observations & measurements 2.Hypothesis formation  theory vs. hypothesis? 3.Tests of the hypothesis  develop experiments for testing 4.Acceptance, modification, or rejection of the hypothesis

  12. Plate Tectonic Theory Lithosphere is divided intoplates that fit like jigsaw puzzle pieces across Earth’s surface.

  13. Plate Tectonics Theory • Continental drift Continents moved across Earth’s surface. (50 yrs+ for acceptance) • Plates float on asthenosphere as they move & they interact along their boundaries. • Plate movement is driven by the unequal distribution of heat w/in Earth. 1) major landscape features (mtns, valleys) 2) distributes natl. resources 3) distribution & evolution of the biosphere

  14. Types of Plate Boundaries CONVERGENT: (subduction zones) **dense plates subduct under less dense plates **subducted plate goes into the mantle & melts

  15. DIVERGENT: (mid-ocean ridges) **seafloor spreading  fractures open, molten mat. from asthenosphere fills fractures

  16. TRANSFORM FAULT: plates move horizontally past one anotherw/out consuming old lithosphere or generating new lithosphere

  17. The Rock Cycle …relates the formation of the major rock groups to internal & external processes

  18. Uniformitarianism[late 1700s] James Hutton — Scottish physician … very intelligent …not able to convey his thoughts “The present is the key to the past.” **Laws that govern the physical, chemical, and biological processes occurring now on the earth, also operated in the past... (i.e., These processes are unchanging through time.) Charles Lyell Principles of Geology(mid 1800s) **noted that processes may have been operating at varying rates in the past or that they may not have had the same significance as they do today

  19. Lower Right: Bird tracks Above: Mudcracks

  20. Geologic Time Scale 19th century geologists arranged info from outcrops based on changes in biota thru time (relative age). • Radiometric dating (20th century) assigned absolute age dates to the sub-divisions.

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