Convergent+Boundaries

Convergent media type="custom" key="10898512"

=**Continental vs. oceanic plate convergence **=
 * In a contest between a dense oceanic plate and a less dense, buoyant continental plate, guess which one will sink? The dense, leading edge of the oceanic plate actually //pulls// the rest of the plate into the flowing [|asthenosphere] and a subduction zone is born! Where the two plates intersect, a deep trench forms. An example of this kind of convergence produces the spectacular volcanic landscape of the Northwest. Off the coast of Oregon, Washington, Alaska and Canada a small plate, the Juan de Fuca, dives beneath North America. This type of convergent plate boundary, called a subduction zone, is known for producing historic earthquakes of great magnitudes.**

MT. Jefferson

=**Oceanic vs. oceanic plate convergence **=
 * In a contest between a dense oceanic plate and a less dense, buoyant continental plate, you know that it’s the dense oceanic plate that sinks. Remember that oceanic plates are born at midocean ridges where molten rock rises from the mantle, cools and solidifies. Little by little, as new molten rock erupts at the mid-ocean ridge, the newly created oceanic plate moves away from the ridge where it was created. The farther the plate gets from the ridge that created it, the colder and denser ('heavier') it gets.****When two oceanic plates collide, the plate that is older, therefore colder and denser, is the one that will sink.** **The rest of the story is a lot like the continental vs. oceanic plate collision we described above. Once again, a subduction zone forms and a curved volcanic mountain chain forms above the subducting plate. Of course, this time the volcanoes rise out of the ocean, so we call these volcanic mountain chains island arcs. The Aleutian Peninsula of Alaska is an excellent example of a very volcanically-active island arc.**

Aleutian Peninsula

=**Continental vs. continental plate convergence **=
 * By this time, you understand enough about plates to guess that when the massive bulk of two buoyant continental plates collide there is bound to be trouble! The Himalayan mountain range provides a spectacular example of continent vs. continent collision. When two huge masses of continental lithosphere meet head-on, neither one can sink because both plates are too buoyant.**

The Himalayan mountain

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