Plate Boundaries and Faults Plates - broken pieces of the crust that float on the athenosphere Plate tectonics - theory that tectonic plates are in constant slow motion – All moving - causes a bit of a traffic jam – A lot of pressure and stress

Plate boundary - place where two plates meet

Faults - break or crack in the crust that plates move along

Normal fault - one plate moves downward against another Creates new crust (happens at Mid-Atlantic Ridge) What kind of stress? Tension - pulling stress – stretches things thin at the middle Divergent Boundary - place where two plates move apart (diverge

Reverse fault - one plate moves upward against another Crust is destroyed Earthquakes happen here What type of stress? – Compression - squeezing stress at convergent boundaries Squeezes until rocks fold or break Convergent Boundary - where two plates come together (converge)

When plates meet… plate densityDepends on plate density – Ocean plates made of basalt - very dense – Continental plates made of granite - not as dense Ocean vs Ocean Ocean vs Continental Continental vs Continental

Continental plate vs Continental plate – Crash head on, same density so mush each other; create folds ( folded mountains) – Can create a plateau – Can create folded mountains

Ocean plate vs Ocean plate – Whichever one is denser sinks into a trench – Subduction - one plate sinks beneath another Ocean plate vs Continental plate – Ocean is denser, so sinks into trench (subduction)

Strike-slip fault - plates slide past each other without moving up or down Crust is not made or destroyed here What type of stress? Shearing - sliding stress Transform Boundary - where two plates slide past each other in opposite directions Earthquake area - WHY?