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Crustal Boundaries Pages 149 - 153

Crustal Boundaries Pages 149 - 153. For starters. We know the Earth is broken into 8 major lithospheric plates …. We know these plates move …. We know there are boundaries between the plates …. Now, let’s look at the three types of boundaries in a little more detail. Basic Vocab.

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Crustal Boundaries Pages 149 - 153

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  1. Crustal BoundariesPages 149 - 153

  2. For starters . . . • We know the Earth is broken into 8 major lithospheric plates …. • We know these plates move …. • We know there are boundaries between the plates …. • Now, let’s look at the three types of boundaries in a little more detail . . .

  3. Basic Vocab . . . • Lithosphere: Earth’s hard outer shell; divided into plates. • Diverging Plate Boundary: Plates are moving apart as new ocean crust is formed ~ most divergent boundaries are found in the ocean. The African and Arabian plates continue to rift apart (diverge), with the result that the Red Sea is ever widening.

  4. Convergent Plate Boundary: Plates moving together/toward each other. Can be subduction or collision; subduction results in the formation of oceanic trenches. • Andes Mountains: Mountain range on the west coast of South America resulting from the collision of two continental plates.

  5. Transform Boundary: Plates sliding past each other. (San Andreas Fault) • Subduction/Subduction Zone: Type of convergent boundary; one plate slips under another plate.

  6. Plate boundaries can be found using page 5 of your ESRT . . . • [Seek and ye shall find!]

  7. Subduction Zones & Earthquakes • The west coast of South America is a subduction zone. • The Nazca Plate (oceanic & more dense ~ 3.0g/cm3) is sliding under the South American plate (less dense ~ 2.7g/cm3). • Earthquakes occur at the boundary between the plates – the earthquakes get deeper as the plate slips farther under . . .

  8. As we move along the line from A (west) to B (east), the depth of the earthquakes increases. as oceanic plate subducts (goes below) under continental plate. A B Depth of Earthquakes * = Shallow  = Intermediate = Deep *  

  9. Earthquake depth increases moving east where the Nazca and South American plates converge. • Earthquake depth increases because the Nazca Plate is subducting under the South American Plate. • The Andes Mountains have formed on the west coast of South America as a result of a convergent collision boundary.

  10. Most divergent plate boundaries are found in the oceans. • The San Andreas Fault is a transform boundary. • A subduction zone is found at a convergent boundary. • New oceanic crust is created at a divergent boundary. • Oceanic trenches are associated with convergent/subduction boundaries.

  11. “Concluding” summary . . . • Divergent boundaries form when two plates are moving away from each other and result in the formation of ridges. • Convergent boundaries occur when two plates are moving toward each other; can be subduction (forming a trench) or collision (forming mountain ranges). • Transform boundaries move horizontally past each other.

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