Plate Tectonics

Tectonic plates: pieces of the Earth’s crust & upper mantle Plate boundaries: places where plates meet

Movement of plates creates forces that affect Earth’s surface at the plate boundaries and causes them to move. Plates move in 3 ways: 1. slide past each other 2. move apart (divergent) 3. collide (convergent)

Sliding Past Faults form when plates slide past each other. Fault: large cracks in rocks that can break Earthquakes happen along fault lines.

San Andreas Fault

Divergent Plates Plates move apart b/c of pulling forces (tension) that act in opposite directions. New crust forms in the gaps where plates pull apart. Form mid ocean ridges (in oceans), and rift valleys (on continents)

Divergent Plates Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates.

Mid-Atlantic Ridge a divergent tectonic plate boundary located along the floor of the Atlantic Ocean the longest mountain range in the world. separates the Eurasian Plate and North American Plate and the African Plate from the South American Plate

Oceanic Ridges

Convergent Plates When plates collide, different things can happen (depends on the density of the plates involved). There can be: continental-continental collisions, oceanic-oceanic collisions & continental-oceanic collisions

Continental-Continental Collisions Forms a mountain range

Oceanic-Continental Collisions Forms a trench and volcanic arc

Oceanic-Oceanic Collisions Forms an island arc

Subduction Zones When one plate plate sinks underneath another plate. The denser plate sinks underneath & into the mantle.

Fold When rocks bend due to force. Can bend upward (anticline) or bend downward (syncline)

Anticline

Syncline a downward-curving fold, with layers that dip toward the center of the structure

Convection the circulation of heat A theory explaining why the plates move. Theory says plates move b/c the mantle material is being circulated b/c of the difference in densities in the mantle.