Module 2 Week 3 Tectonic Features


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Module 2 Week 3 Tectonic Features

  1. 1. Tectonic Features Orogeny, Volcanism, and Earthquakes
  2. 2. Overview <ul><li>Orogeny </li></ul><ul><ul><li>Plate Boundaries and Mountain Building </li></ul></ul><ul><li>Volcanism </li></ul><ul><ul><li>Types of Volcanoes </li></ul></ul><ul><ul><li>Properties of Volcanoes </li></ul></ul><ul><ul><li>Plate Boundary Associations </li></ul></ul><ul><li>Earthquakes </li></ul><ul><ul><li>Earthquakes and Faults </li></ul></ul><ul><ul><li>Earthquake Properties </li></ul></ul><ul><ul><li>Earthquake Damage </li></ul></ul>
  3. 3. Orogeny <ul><li>Important orogenies </li></ul><ul><ul><li>Allegheny Orogeny: Appalachian and Ozark Mountains; 250 – 300 million years ago </li></ul></ul><ul><ul><li>Sierra Nevadan Orogeny: produced the Sierra Nevada; 130 –160 million years ago </li></ul></ul><ul><ul><li>Alpine Orogeny: produced the Alps; 20 –120 million years ago </li></ul></ul><ul><ul><li>Laramide Orogeny: produced Rocky Mountains; 40 – 80 million years ago </li></ul></ul><ul><ul><li>Himalayan Orogeny: Produced the Himalayas; 45-50 million years ago </li></ul></ul>
  4. 4. Types of Orogenies <ul><li>Associated with subduction zones </li></ul><ul><li>Oceanic plate-continental plate collisions </li></ul><ul><ul><li>Andes, Sierra Madre, Rocky Mountains </li></ul></ul><ul><ul><li>Folded sedimentary strata, igneous intrusions, terranes, volcanism </li></ul></ul><ul><li>Oceanic plate-oceanic plate collisions </li></ul><ul><ul><li>Produce volcanic islands </li></ul></ul><ul><ul><li>Most of the islands arcing around the Pacific Rim; Indonesia, Aleutians, Japan </li></ul></ul><ul><li>Continental plate-continental plate collisions </li></ul><ul><ul><li>Himalayas, Alps </li></ul></ul><ul><ul><li>Intense folding, overthrusting, faulting and uplifting </li></ul></ul>
  5. 10. Volcanoes <ul><li>Volcanic landforms </li></ul><ul><ul><li>Cinder cones, calderas, shield volcanoes, plateau basalts, composite volcanoes </li></ul></ul><ul><ul><li>Calderas form on any volcano when the original structure collapses </li></ul></ul><ul><li>Locations of volcanic activity </li></ul><ul><ul><li>Subduction boundaries (c-o, o-o) </li></ul></ul><ul><ul><li>Seafloor spreading and rifts </li></ul></ul><ul><ul><li>Hot spots </li></ul></ul><ul><li>Types of eruptions </li></ul><ul><ul><li>Effusive </li></ul></ul><ul><ul><li>Explosive </li></ul></ul><ul><li>Eruption material </li></ul><ul><ul><li>Lava </li></ul></ul><ul><ul><li>Pyroclastic material (tephra): ash, dust, cinders, scoria, pumice and aerial bombs </li></ul></ul><ul><ul><li>Gases </li></ul></ul>
  6. 11. Effusive Eruptions <ul><li>Gentle eruptions producing mostly lava and gases </li></ul><ul><ul><li>magma direct from the asthenosphere </li></ul></ul><ul><ul><li>low-viscosity and fast flowing </li></ul></ul><ul><ul><li>produces basalt </li></ul></ul><ul><li>Landforms </li></ul><ul><ul><li>Shield Volcanoes </li></ul></ul><ul><ul><ul><li>gentle slopes, gradually rising to a summit crater </li></ul></ul></ul><ul><ul><ul><li>Often associated with hotspots </li></ul></ul></ul><ul><ul><li>Plateau Basalts </li></ul></ul><ul><ul><ul><li>Associated with rifts </li></ul></ul></ul><ul><ul><ul><li>Magma spreads out across surface </li></ul></ul></ul>
  7. 19. Explosive Eruptions <ul><li>Violent, explosive eruptions </li></ul><ul><ul><li>Associated with subduction zones </li></ul></ul><ul><ul><li>Thick, viscous magma rising from subducted plates clogs vents in the volcano, allowing gases to build up to an explosion </li></ul></ul><ul><li>Landforms </li></ul><ul><ul><li>Cinder cones </li></ul></ul><ul><ul><ul><li>less explosive eruptions </li></ul></ul></ul><ul><ul><ul><li>pyroclastic material builds up into a conical shape </li></ul></ul></ul><ul><ul><li>Composite volcanoes (stratovolcanoes) </li></ul></ul><ul><ul><ul><li>More explosive </li></ul></ul></ul><ul><ul><ul><li>Eject alternating layers of lava and pyroclasts, creating composite strata </li></ul></ul></ul><ul><ul><ul><li>Steep sides, conical shape, often very symmetrical </li></ul></ul></ul><ul><ul><ul><li>Mt. St. Helens </li></ul></ul></ul>
  8. 23. Earthquakes <ul><li>Caused by motion along faults </li></ul><ul><ul><li>Elastic rebound theory </li></ul></ul><ul><ul><ul><li>Friction holds fault blocks motionless until strain exceeds friction </li></ul></ul></ul><ul><ul><ul><li>Sudden motion, at a point ( asperity ), releasing energy </li></ul></ul></ul><ul><ul><li>The point in the earth where the slippage occurs is called the focus </li></ul></ul><ul><ul><li>The point on the surface directly above the focus is called the epicenter . </li></ul></ul><ul><li>The strength of an earthquake felt at any given point depends on </li></ul><ul><ul><li>Depth to the focus </li></ul></ul><ul><ul><li>Distance to the epicenter </li></ul></ul><ul><ul><li>Amount of energy released </li></ul></ul><ul><ul><li>Geological material; bedrock is better than loose sediments because of liquefaction </li></ul></ul>
  9. 25. Surface Fault Epicenter Focus
  10. 26. Measuring Earthquakes <ul><li>Mercali scale </li></ul><ul><ul><li>1902 </li></ul></ul><ul><ul><li>Intensity </li></ul></ul><ul><ul><li>Qualitative </li></ul></ul><ul><li>Richter scale </li></ul><ul><ul><li>1935 </li></ul></ul><ul><ul><li>Wave Amplitude </li></ul></ul><ul><ul><li>Quantitative </li></ul></ul><ul><ul><ul><li>Logarithmic: each number represents a ten fold increase in amplitude, and a 31.5 increase in energy. </li></ul></ul></ul><ul><li>Moment Magnitude scale </li></ul><ul><ul><li>1993 </li></ul></ul><ul><ul><li>Fault slippage, surface disturbance, geologic material </li></ul></ul><ul><ul><li>Quantitative </li></ul></ul>
  11. 29. After-Affects of Earthquakes <ul><li>Topographic changes in elevation </li></ul><ul><ul><li>Valdiva, Chile, 1960: 400 km 2 area dropped 7–9 meters </li></ul></ul><ul><li>Tsunamis </li></ul><ul><ul><li>Tallest measured wave: 70 meters </li></ul></ul><ul><ul><li>December 26, 2004 – Indian Ocean </li></ul></ul><ul><ul><ul><li>9.0 Magnitude quake off of Sumatra moves the island 150 ft West </li></ul></ul></ul><ul><ul><ul><li>triggered a tsunami with a large inland surge </li></ul></ul></ul><ul><ul><ul><li>Quake and Tsunami combined killed over 250,000 people </li></ul></ul></ul><ul><li>Catastrophic rockslides </li></ul><ul><li>Landslides </li></ul>