Plate Boundaries and Landforms that are created there Plate Tectonics Plate Boundaries and Landforms that are created there

Plate Tectonics Theory - Wegener The earth is made up of rigid slabs of rock, or plates the move with respect to each other. These plates “float” on the hot, semi-plastic mantle – in a balanced state known as “Isostasy.” The Lithosphere is made of these plates and the upper most mantle. The “plates” are like puzzle pieces

Evidence for Plate Tectonics GPS – Global Positioning System Satellites can measure the distances and speeds that the plates are moving. Evidence of magnetic reversal in the rocks Similar fossil evidence on different continents

Plate Boundaries Divergent Boundaries Where two plates are going away from each other Forms the Mid Ocean Ridge if in the ocean Forms Rift Valleys if over a continent

Plate Boundaries Transform Boundaries Where two plated slide past each other San Andreas Fault is the most famous. Stress builds and then earthquakes happen when the pressure is released.

Plate Boundaries Convergent Boundaries When two plates collide with each other. The denser one can slide under the other at Subduction Zones which created Ocean trenches. Volcanoes usually line the edges of this boundary Continent vs. Ocean = Subduction Zone Ocean vs. Ocean = Volcanic Islands Continent vs. continent = Mountain Ranges - Himalayas

Plate Motion Convections Currents The circulation of material caused by differences in temperatures. Warm rises and cold sinks

Plate Motion Basal Drag – Asthenosphere pulls the lithosphere like a conveyor belt Ridge Push – Rising mantle pushed the plates away from each other with gravity Slab Pull – Sinking plates at a subduction zone pulls the plate downward Still not sure which one has a greater effect on the movement of the continents

Plate Motion

Up and Down Motion Subsidence – Downward vertical motion from force of ice on top of the continents Uplift – upward vertical motion which happens when the ice melts and the continent rises

Horizontal Motion Three type of stress: Compression – Squeezing together – equal in the middle Tension – Pulling apart equal in the middle Shear - top in one direction bottom in the other