The Theory of Plate Tectonics Chapter 5 Lesson 3

What is the Theory of Plate Tectonics? The theory of plate tectonics states that Earth’s plates are in slow, constant motion, driven by convection currents in the mantle.

Plate Boundaries Earth’s plates meet at boundaries. Along each boundary, plates move in one of three ways. 1. Apart – Divergent boundary 2. Together- Convergent boundary 3. Past each other – Transform boundary Plates move between 1-12 cm per year, which is about how fast your fingernails grow. Faults- are breaks in Earth’s crust where rocks have slipped past each other

Transform Convergent Divergent

Divergent boundaries – two plates moving slowly apart form a rift valley

Transform Boundaries are where two plates slip past each other moving in opposite directions. Earth quakes result from this type of boundary

New basaltic magma rises to the surface along the ridge forming new oceanic crust

Convergent Plate boundaries – plates moving toward each other Convergent Plate boundaries – plates moving toward each other. Three types of convergent boundaries 1. Oceanic crust meets Oceanic crust 2. Oceanic crust meets Continental crust 3. Continental crust meets Continental crust

Ocean-Ocean- forms a trench – more dense material will sink under the less dense material

Trench Island arc These trenches result in an Island Arc. Japan is an example of an Island Arc system Trench Island arc

Ocean crust converging with continental crust Results in volcanic arc and a trench

Oceanic - continental convergence E.g. Andes mountains

Continental-continental convergence results in mountain ranges.

The Andes

The sub-continent of India has collided with the Eurasian continent to form the Himalayas

Eurasian Plate Indian Plate