3.4Plates converge or scrape past each other

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3.4Plates converge or scrape past each other

  1. 1. Plates converge or scrape past each other
  2. 2. Tectonic plates push together at convergent boundaries. <ul><li>Here crust is either folded or destroyed </li></ul><ul><li>When one plate sinks beneath another , it is called subduction . </li></ul>
  3. 3. Three types of convergent boundaries <ul><li>a. Where continental plates meet </li></ul><ul><li>b. Where two oceanic plates meet </li></ul><ul><li>c. Where oceanic and continental plates meet </li></ul><ul><li>Most major geologic events occur at all three types of boundaries. </li></ul>
  4. 4. Continental-Continental Collision <ul><li>1. Occurs when two plates carrying continental crust push together </li></ul><ul><li>2. Both plates are the same density, so crust folds and crumples along the edges </li></ul><ul><li>3. In some cases, the folded crust can be pushed up high enough to form mountains </li></ul>
  5. 5. Oceanic-Oceanic Subduction <ul><li>1. Occurs when one plate with oceanic crust sinks (subducts) under another plate with oceanic crust </li></ul><ul><li>a. The older plate sinks because it is colder and denser </li></ul><ul><li>b. Older crust melts in the asthenosphere under intense heat </li></ul>
  6. 6. Oceanic-Oceanic Subduction <ul><li>Deep ocean trenches </li></ul><ul><ul><li>Deep canyons that form on the ocean floor as a plate sinks </li></ul></ul><ul><ul><li>Most are found in the Pacific Ocean </li></ul></ul>
  7. 7. Oceanic-Oceanic Subduction <ul><li>Island Arcs </li></ul><ul><ul><li>Chains of volcanic islands that form on the top of the plate, parallel to a deep-ocean trench </li></ul></ul>
  8. 8. Oceanic-Continental Subduction <ul><li>Occurs when ocean crust sinks under continental crust </li></ul><ul><ul><li>This crust sinks because it is colder and denser than the continental crust </li></ul></ul><ul><ul><li>Deep-ocean trenches form here, along with coastal mountains </li></ul></ul>

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