GLG 112 Lecture Notes - Lecture 2: Convergent Boundary, Subduction, Seafloor Spreading
Document Summary
Theory that earth"s lithosphere co(cid:374)sists of large, rigid plates that (cid:373)ove about one another. Moved by flow from asthenosphere plastic solid. Divergent boundaries: , two plates move away from each other. Convergent: , two plates move into each other. Ta: comes in the form of eqs and/or volcanoes occurs at plate boundaries. Active boundaries: 2 tectonic plates moving about one another creating tectonic activity. Passive boundaries: passive margin, no tectonic activity because no plates moving about one another. Heat rises from below, underlying rock melts comes to the surface and creates new lithosphere (new land created) Process: lava/molten rock fills the void when plates move apart new oceanic crust is created when lava cools new crustless dense, creates mid-ocean ridge (long volcanic mountain chains) (5km thick) As land is being pulled apart, it thins and eventually becomes so thin it is below sea level (35-40km thick) *continental rifting often turns into seafloor spreading.
