Plate Tectonics

Theory of Plate Tectonics  Earth’s crust and part of the upper mantle are broken into sections  Sections of Earth’s crust = PLATES

Lithosphere Rigid layer of earth, made up of the crust and a part of the upper mantle

Asthenosphere Plasticlike layer below the lithosphere where plates float and move around

Plate Boundaries 1. DIVERGENT BOUNDARIES 2. CONVERGENT BOUNDARIES 3. TRANSFORM BOUNDARIES

Divergent Boundary  The boundary between two plates that are moving apart  TENSION- force that pulls the plates Features caused by divergent boundaries: Rift valleys and mid-ocean ridges

Convergent Boundary  When two plates collide (move towards each other)  COMPRESSION- force that pushes the plates. Features caused by convergent boundaries: Mountains and earthquakes

Subduction Zone  When an oceanic plate converges with a less dense continental plate, the denser oceanic plate sinks under the continental plate Features caused by subduction zones: Volcanoes

Transform Boundary  When two plates slide past one another (plates move in opposite directions)  SHEARING- force in transform boundary eatures caused by transform boundaries: Earthquakes, faults

Types of Faults Normal fault = the rock layers above the fault move down when compared with rock layers below the fault Reverse fault = the rock layers above the fault surface move up relative to the rock layers below the fault Strike-slip fault = rocks on opposite sides of the fault move in opposite directions, or in the same direction at different rates

Cause of Plate Tectonics  Convection (heat) = causes the movements of plates  Convection current: cycle of heating, rising, cooling, and sinking

Testing for Plate Tectonics Problem: Studying magnetic characteristics of rocks, volcanoes and earthquakes supported the theory but did not provide PROOF. Solution: New methods discovered to measure amounts of plate movement = satellites and lasers