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Chapter 2 section 3 Chapter 2 section 3 Presentation Transcript

  • Internal Forces Shaping the Earth
  • I. Plate Tectonics A. The Earth Moves 1. Tectonic plates are massive, moving pieces of Earth’s lithosphere. 2. Plates ride above circulating, heated rock. 3. Geographers study plate movements to understand: a. how the earth is reshaped. b. how earthquakes and volcanoes are formed.
  • B. Plate Movement 1. Plates move in one of four ways: a. by spreading, or moving apart. b. subduction, or diving under another plate. c. collision, or crashing together. d. sliding past each other in a shearing motion. View slide
  • 2. Movement of plates effects surface of the earth. 3. Saudi Arabia–Egypt’s plates are spreading apart, widening Red Sea. 4. India’s plate is crashing into Asian continent, building up Himalayas. 5. Three types of boundaries mark plate movement:. a. divergent boundary b. convergent boundary c. transform boundary View slide
  • D. Folds and Faults 1. Two plates meeting can cause folding, cracking of rock. 2. Fault occurs when pressure causes rock to fracture, or crack. 3. Fault line is place where plates move past each other.
  • II. Earthquakes A. The Earth Trembles 1. An earthquake occurs when plates grind or slip at a fault line. 2. A seismograph detects earthquakes and measures the waves they create. B. Earthquake Locations 1. Location in the earth where an earthquake begins is called the focus . 2. Epicenter—the point directly above focus on the earth’s surface. 3. Nearly 95% of earthquakes occur at tectonic plate boundaries
  • C. Earthquake Damage 1. Earthquakes release energy in the form of motion, causing: a. Landslides b. land displacement c. fires (broken gas lines) d. collapsed buildings 2. Richter Scale—numeric scale showing relative strength of earthquake. D. Tsunami 1. Tsunami, a giant ocean wave, begins at epicenter of an earthquake: a. travels at up to 450 mph. b. waves of 50–100 ft. or higher.
  • III. Volcanoes A. The Explosive Earth 1. Volcano—underground materials pour from crack in the earth’s surface. 2. Most volcanoes occur at tectonic plate boundaries. B. Volcanic Action 1. Eruption—lava, gases, ash, dust, explode from vent in Earth’s crust. 2. Lava—magma that has reached the earth’s surface; may create landform.
  • C. Ring of Fire 1. Ring of Fire—zone around rim of Pacific Ocean: a. meeting point of eight tectonic plates. b. vast majority of the earth’s active volcanoes located here. 2. ―Hot spots‖ are where magma rises to surface from mantle. 3. Hot springs, geysers indicate high temperatures in earth’s crust. 4. Some volcanic action is useful: a. volcanic ash produces fertile soil. b. hot springs are tapped for heat, energy.