GEOL 303 Lecture 4: Geology 303 Lecture 4
Document Summary
Plate tectonics - rigid lithosphere is subdivided into eight large plates and several smaller plates that move about the glove and interact with each other at plate tectonic boundaries. Divergent boundaries - plates move away from one another and oceanic crust is created. Are coincident with the mid oceanic ridges (mors) As the lithospheric plates move apart, asthenosphere rises and melts to produce basaltic magma, which then cools to produce oceanic crust. The only mid-atlantic ridge we can see is in iceland. Convergent boundaries - plates move toward one another and oceanic crust is destroyed. Subduction - one plate descends into the mantle as the plates converge. Subduction results in melting above the down-going slab, so that a belt of active, subduction- generated volcanoes will always be present to the oceanic trench. Forms the crest of the andes mountains, parallel to the peru-chile trench along the western margin of south america. You cannot subduct continental crust, only oceanic crust (important)
