Module 2 Week 2 Crustal Processes


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Module 2 Week 2 Crustal Processes

  1. 1. Crustal Processes
  2. 2. Overview <ul><li>Orders of relief </li></ul><ul><ul><li>Topographic regions </li></ul></ul><ul><li>Crustal Formation </li></ul><ul><ul><li>Oceanic and Continental crust </li></ul></ul><ul><ul><li>Displaced terranes </li></ul></ul><ul><li>Crustal Deformation </li></ul><ul><ul><li>Folding </li></ul></ul><ul><ul><li>Faults </li></ul></ul><ul><ul><li>Landforms </li></ul></ul>
  3. 3. Orders of Relief <ul><li>Relief refers to the relative difference in height between objects on the landscape (specifically, the difference in height between the highest and lowest point) </li></ul><ul><ul><li>Plains: low relief </li></ul></ul><ul><ul><li>Mountainous areas: high relief </li></ul></ul><ul><li>Topography : Variation in the relief of the Earth’s surface </li></ul><ul><li>Orders of Relief : classification of landscape by spatial scale </li></ul>
  4. 4. First Order of Relief <ul><li>Continental platforms </li></ul><ul><ul><li>The above-water landmasses </li></ul></ul><ul><ul><li>The continental shelves </li></ul></ul><ul><li>Ocean basins </li></ul>
  5. 6. First order relief: ~ 9000 – 10,000 meters
  6. 7. Second Order of Relief <ul><li>On continents: </li></ul><ul><ul><li>continental masses (Edward’s Plateau) </li></ul></ul><ul><ul><li>mountain masses (Rocky Mts, Alps, Sierra Nevada) </li></ul></ul><ul><ul><li>plains (the Great Plains) </li></ul></ul><ul><ul><li>lowlands (west Siberia) </li></ul></ul><ul><li>Oceans </li></ul><ul><ul><li>continental rises and slopes (the slope of the continental shelf) </li></ul></ul><ul><ul><li>abyssal plains, mid-oceanic ridges, submarine canyons, subduction trenches </li></ul></ul>
  7. 8. Third Order of Relief <ul><li>Most detailed order of relief </li></ul><ul><li>Individual features on the landscape </li></ul><ul><ul><li>single mountains, valleys, rivers, etc. </li></ul></ul><ul><ul><li>Mt. St. Helens, Lake Travis, etc. </li></ul></ul>
  8. 9. Topographic Regions of the World <ul><li>A classification system of second order features based on relief </li></ul><ul><li>Six categories </li></ul><ul><ul><li>Plains </li></ul></ul><ul><ul><ul><li>Local relief less than 100 meters </li></ul></ul></ul><ul><ul><li>Hills and Low Tablelands </li></ul></ul><ul><ul><ul><li>Hills: Relief between 100 and 600 meters </li></ul></ul></ul><ul><ul><ul><li>Low Tablelands: Elevation less than 1500 meters, relief less than 100 meters (an elevated plain) </li></ul></ul></ul><ul><ul><li>High Tablelands </li></ul></ul><ul><ul><ul><li>Elevation greater than 1500 meters, relief less than 300 meters </li></ul></ul></ul><ul><ul><ul><li>Canyons are often a feature of high table lands </li></ul></ul></ul><ul><ul><li>Mountains: Relief greater than 600 meters </li></ul></ul><ul><ul><li>Widely Spaced Mountains </li></ul></ul><ul><ul><ul><li>Discontinuous or solitary with 600 meter plus relief; intervening spaces have relief less than 150 meters </li></ul></ul></ul><ul><ul><li>Depressions: Basins surrounded by other features </li></ul></ul>
  9. 11. Crustal Formation <ul><li>Three categories of continental crust </li></ul><ul><ul><li>Residual mountains and continental cores from past tectonic activity </li></ul></ul><ul><ul><ul><li>Inactive </li></ul></ul></ul><ul><ul><ul><li>Continental cores (shields) or the original crust around which the rest of a continent’s crust forms </li></ul></ul></ul><ul><ul><ul><li>Terranes: migrating pieces of crust that merge with larger continents </li></ul></ul></ul><ul><ul><ul><ul><li>Much of the west coast is terranes, esp. Alaska, British Columbia and Mountain West </li></ul></ul></ul></ul><ul><ul><li>Active tectonic features: mountains, folding, faulting </li></ul></ul><ul><ul><ul><li>New crust formed from seafloor spreading and subduction </li></ul></ul></ul><ul><ul><li>Volcanic features </li></ul></ul>
  10. 15. Crustal Deformation <ul><li>All rock types experience stress </li></ul><ul><li>Sources of stress </li></ul><ul><ul><li>Tectonic forces </li></ul></ul><ul><ul><li>Gravity </li></ul></ul><ul><ul><li>Weight of overlying rocks </li></ul></ul><ul><li>Types of Stress </li></ul><ul><ul><li>Tension </li></ul></ul><ul><ul><li>Compression </li></ul></ul><ul><ul><li>Shear </li></ul></ul><ul><li>Strain: how rocks respond to stress </li></ul><ul><ul><li>folding – pliable layers </li></ul></ul><ul><ul><li>faulting – rigid layers: normal, reverse, and strike-slip </li></ul></ul>
  11. 19. Folding <ul><li>Folding occurs in response to compression </li></ul><ul><li>Strata folded into a series of anticlines and synclines </li></ul><ul><ul><li>Anticline </li></ul></ul><ul><ul><ul><li>Antiform: young > old > young </li></ul></ul></ul><ul><ul><li>Syncline </li></ul></ul><ul><ul><ul><li>Synform: old > young > old </li></ul></ul></ul><ul><li>Domes and Basins </li></ul>
  12. 21. Surface: Antiform Profile: Anticline
  13. 22. Surface: Synform Profile: Syncline
  14. 27. Faulting <ul><li>Rock strata fracture when stresses are too great to be compensated for by folding </li></ul><ul><li>Displacement of strata on either side of fracture is called a fault </li></ul><ul><ul><li>Normal Fault </li></ul></ul><ul><ul><ul><li>Hanging wall slips below foot wall </li></ul></ul></ul><ul><ul><li>Reverse and Thrust Fault </li></ul></ul><ul><ul><ul><li>Hanging wall raised above foot wall </li></ul></ul></ul><ul><ul><li>Strike-Slip Fault </li></ul></ul><ul><li>Faulting occurs in sudden episodes which release energy, triggering earthquakes </li></ul>
  15. 33. Horst and Graben <ul><li>Systems of normal faults producing alternating ridges and valleys </li></ul><ul><li>Characteristic of the Basin and Range area of the western US. </li></ul>