Bellringer: 10/12/15 Make 2 columns labeled constructive and destructive. List as many features of the Earth's crust as you can. Place them under constructive or destructive. We’ll take a pretest today.

Bellringer 10/13/15 Yesterday, you thought about land features that may be formed from constructive and destructive forces. Many seem to be familiar with plate tectonics. Describe what you think plate tectonics is?

Bellringer 10/14/15 Describe the convection currents in a boiling pan of water.

17.4 Cause of Plate Motions

Asthenospere (lower mantle and upper core) Earth’s interior between the upper core and the lithosphere (crust and upper mantle) Large-scale motion is believed to be the mechanism that drives the movement of tectonic plates

Convection Transfer of thermal (heat) energy by the movement of heated material from one place to another –Ex. Boiling water Heat comes from radioactivity and pressure (friction) within the mantle

Convection Currents Cycle of warm (less dense) mantle rising and cool (more dense) mantle sinking –The cooling of matter causes it to contract slightly and increase in density –then it sinks due to gravity –Warmed matter is then displaced and forced to rise

Convection Currents Develop in the asthenosphere Move the crust and outermost part of the mantle (lithosphere) Transfer thermal energy from Earth’s interior to its exterior

Rising material spreads out, lifts and splits lithosphere at divergent boundaries Downward movement pulls convergent boundaries

Ridge push Tectonic process associated with convection currents Occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone

Slab pull Tectonic process associated with convection currents in Earth’s mantle Occurs as the weight of the subducting plate pulls the trailing lithosphere into a subduction zone.