ESCI 1001 Lecture Notes - Lecture 5: Oceanic Crust, Oceanic Basin, Seafloor Spreading
Document Summary
Mantle plums have origins near the mantle-core boundary. Whole-mantle convection: plate recycling extends to the core-mantle boundary. Stratified convection: the lower mantle convects more sluggish than the upper mantle. Boundary near 700 km separates the two convection systems. Because older plates are colder, denser, they try to subduct and are being pulled downward. Plates are riding the convection of mantle. There is a sheet of colder material (lithosphere) that"s going down to the core-mantle boundary. Rifting within a continent splits the continent. Leading to the opening of a new ocean basin and creation of new oceanic crust, starting the cycle. As seafloor spreading continues and an ocean opens, passive margin cooling occurs and sediment accumulates. Convergence begins; oceanic crust is subducted beneath a continent, creating a volcanic mountain belt at the active margin. Terrane accretion- from the sedimentary accretionary wedge or fragments carried by the subducting plate-welds material to the continent.
