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I. PLATE BOUNDARIES CREATE EARTH'S TOPOGRAPHY AND GEOLOGIC EVENTS
   A. CONVERGENT BOUNDARIES - plates collide with each other
     1. Three types of collisions occur at CB
       a. If an oceanic crustal plate collides with an oceanic crustal
 
plate it creates:
        1) Trench - hole formed as older oceanic plate is sucked downwards 
         2) VOLCANIC ISLAND CHAIN forms parallel to trench 50-200 miles away
                      a) Subducted plate melts into magma and rises through 
cracks to form
                           a line of volcanoes that rise from ocean floor an
d 
 poke through ocean 
                3) Large earthquakes called MEGAQUAKES occur when plates 
“unstick”
             a) Megaquake can cause a large water surge called a TSUNAMI  
        4) OCB Locations: Indonesia, Japan, Aleutian Islands
            b. If a continental crustal plate collides with a continental 
crustal plate it creates
        1)  FOLDED MOUNTAINS - mountains made of bent rocks
                      a) Mountain rocks are being COMPRESSED or squeezed.
                      b) Up folds are called ANTICLINES and down folds are 
SYNCLINES
                      c) Usually made of continental shelves pushed up above
 
water.
                          1) CONTINENTAL SHELF - unseen continent edge 
covered by ocean
                          2) Ocean fossils and rocks are seen at the top of 
these mountains
                  2) REVERSE FAULT  MOUNTAINS - block of crust being 
“squeezed up”
                                      along reverse faults 
              a) FAULT- crack between two pieces of crust that are moving  
                          1) REVERSE FAULT -compression forces cause the 
HANGING WALL 
                                                                   to slide 
up the FOOT WALL 
                          2) Earthquakes occur when walls “unstick
” and move 
vertically
                               (a) SCARP - cliff showing where crust has 
cracked and moved
                   3) CCB Locations: Himalayas in India, Alps in Europe
             c. If oceanic crustal plate collides with a continental crustal
 
plate it creates:
                   1)  All of the above.
                   2)  COCB Location: South and North America
       B. DIVERGENT BOUNDARIES - plates are pulled away from each other
           1. Two types of  pull aparts occur at DB
             a. If oceanic crust pulls away from oceanic crust it creates:
                  1) Rift Valley  as earth pulls apart
                  2) Volcanoes form when magma erupts through fissures in 
rift valley
                  3) ODB Location:  Iceland        
             b. If continental crust pulls away from continental crust it 
creates
         1) Small Volcanoes
                 2) Rift valley  - also called NORMAL FAULT VALLEY 
                      a) Block of land sinking along normal faults due to 
tension forces 
                           (1) TENSION - force pulling land aprt
                           (2) NORMAL FAULT - hanging wall slides down the 
foot wall 
                       b) Earthquakes occur when walls “unstick�
�� and lurches 
downwards
                       c) Asthenosphere pushes lightened fault blocks upward
s 
and heavier
                           block sinks deeper   
                  3) Examples: Africa and Eastern California                
  
                                                         
           3. When oceanic or continental plates slide past each other it 
creates:
       a. STRIKE SLIP FAULT - sideways moving fault due to shear forces
                  1) SHEAR FORCES - force that pushes rocks sideways  
                  2) Walls move horizontality - not vertically
                  3) Earthquakes occur when land un”sticks” 
and slip sideways
               b. Examples: California and Turkey



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