Plate Movement and Plate Boundaries Chapter 4, Section 3
Plate Tectonics Theory Lithosphere is divided into plates Plates move around on the asthenosphere
3 Causes of plate motion
Slab Pull Oceanic plate sinks (more dense) Pulls rest of tectonic plate with it
Ridge Push Oceanic crust is higher at ridge Pushes plate underneath continent
Convection Happens in asthenosphere Hot magma rises, cool magma sinks Drags plates sideways
3 Types of Plate Boundaries Convergent Divergent Transform Fault
Convergent Boundaries
Continent / Continent Plates thicken and buckle Push upwards Mountain formation
Continent / Oceanic Oceanic plate sinks (more dense) Subduction zone Trenches form Volcanic mtns on coast
Oceanic / Oceanic One slides under the other Subduction zones Volcanic Islands
Divergent Boundary Plates spread apart Magma rises New lithosphere formed Mid – Atlantic Ridge
Transform Boundary Plates slide past each other Produce earthquakes
Types of Plate Boundaries: DivergentConvergentTransform
Continent / Continent Examples Appalachian Mtns. Atlas Mtns.
Continent / Oceanic Examples Andes Cascades Mt. St. Helens
Oceanic / Oceanic Examples Aleutians Japan Philippines
Plate Movement Approx. 3-6 cm per year Rate a fingernail grows!