PLATE BOUNDARIES.pptx

Plate Tectonics It is not the continents that are moving, but the “PLATES” of lithosphere “FLOATING” in effect on the asthenosphere The lithosphere is made up of about 20 PLATES which move relative to each other in several ways An overview of the tectonic system.  Plate Boundaries...

Plate Tectonics It is not the continents that are moving, but the “PLATES” of lithosphere “FLOATING” in effect on the asthenosphere The lithosphere is made up of about 20 PLATES which move relative to each other in several ways An overview of the tectonic system.  Plate Boundaries  Plate Boundaries Tectonic plates can move between one and 10 centimeters per year, on top of asthenosphere. The region between Plates are aptly called PLATE BOUNDARIES.  Why Plate Boundaries are important? Plate boundaries are important because they are often associated with earthquakes and volcanoes. Most seismic activity occurs at three types of plate boundaries—DIVERGENT, CONVERGENT, AND TRANSFORM.  Types of Plate Boundaries Divergent Plate Boundary Two plates that move away from each other create a gap or a rift between them. Produce mid-ocean ridges, refer to the mountain ranges under water like Iceland or continental rift zone like the African Rift Valley  ICELAND: An example of continental rifting  Iceland has a divergent plate boundary running through its middle, North American Plate and Eurasia Plate diverging. East Africa Rift Valley  Convergent Plate Boundary Plates are moving towards each other and form either a subduction zone or orogenic belt.  Subduction Zone – if one plate moves underneath the other.  Orogenic Belt – if the two simply collide and compress. Oceanic-Oceanic Convergence When two oceanic plates collide, a subduction zone is formed. The descending oceanic plate begin to melt upon contact with asthenosphere. The molten material begins to rise, creating a chain of volcanoes. Mariana Trench Oceanic-Continental Convergence  When an oceanic plate collides with continental plate, the oceanic plate subduct beneath the continental plate, possibly forming a trench.  Oceanic lithosphere heats and Deep Ocean dehydrates as it subsides Trench  The melt rises forming volcanism  Volcanic mountains also develop on land. Andes Mountains in South America Cascade Range in North America Continental-Continental Convergence When two continental plates collide, no subduction happens. Instead, the plates collide and push upwards forming large mountain ranges. European Alps, Himalayas HIMALAYAS  ALPS in Europe Collision of Africa and Eurasia  Transform Plate Boundary This shows the San Andreas Fault. It is a transform fault boundary, the plates slides against each other in opposite direction. No mountains or volcanoes are produced. Instead, earthquakes result from the movement of plates, and release massive amounts of energy. Transform Plate Boundary  Review of Types of Boundaries  Divergent (Plates are moving away from each other) mid ocean ridge like Iceland or continental rift zone like the African Rift Valley  Convergent (Plates are moving towards each other) Ocean/ocean like Japanese Islands Continent/ocean like Andes and Cascades Continent/continent like the Himalayas  Transform fault (Plates are moving past/slide each other) San Andreas fault  Hot spots are not at plate boundaries, but give us information about plate motion  What causes Tectonic Plate?  Convection in the mantle, as the plastic asthenosphere flows, carrying the plates with it.  This is probably aided by slab pull at subduction zones and ridge push at mid ocean ridges and rising plumes in the mantle.  This diagram shows several different model hypotheses.