Download types of plate boundaries

TYPES OF PLATE BOUNDARIES
I. DIVERGENT BOUNDARIES
DIVERGENT means moving apart – so divergent plate boundaries are places where
two plates move away from each other
THIS ALLOWS MAGMA TO REACH THE EARTH’S SURFACE – VOLCANOS
AND/OR EARTHQUAKES CAN OCCUR AT DIVERGENT BOUNDARIES
THE LANDFORMS THAT FORM AT DIVERGENT BOUNDARIES DEPEND ON
THE TYPES OF PLATES THAT ARE MOVING APART:
A. RIFT VALLEYS: form when two THE PLATES THAT ARE MOVING APART
ARE CONTINENTAL PLATES. This process is called RIFTING.
As the crust deforms and stretches, THE EXPANDING RIFT BECOMES A RIVER
VALLEY. (Africa’s Great Rift Valley, the Connecticut River Valley)
B. UNDERSEA RIDGE – RIFT SYSTEMS will form when THE PLATES THAT ARE
MOVING APART ARE / BECOME OCEANIC PLATES. Lava will flow up
through the gap between the plates (rift) and form mountains on either side of
the rift (called ridges)
*** SEAFLOOR SPREADING IS THE NAME OF THIS PROCESS – it can also produce
EARTHQUAKES AND VOLCANOS ***
***THE MID ATLANTIC RIDGE IS A RIFT – RIDGE SYSTEM FOUND AT DIVERGENT
PLATE BOUNDARIES, AND IS A RESULT OF THE PROCESS OF SEAFLOOR
SPREADING***
II. CONVERGENT BOUNDARIES
CONVERGENT means coming together – so convergent plate boundaries are
places where two plates collide
WHAT HAPPENS TO THE PLATE EDGES WHEN THEY COLLIDE DEPENDS ON
WHETHER THE PLATE EDGES ARE CONTINENTAL OR OCEANIC, AND THEIR
DENSITIES (ocean plates are denser):
II. CONVERGENT BOUNDARIES continued
A. FOLDING: occurs when two plates of EQUAL DENSITY COLLIDE;
the edges of the plates will BUCKLE UPWARDS – FORMING
FOLDED MOUNTAINS (Appalachians, Himalayas)
***FOLDING OCCURS WHEN TWO CONTINENTAL PLATES COLLIDE (cont. plates
are = in density)***
B. SUBDUCTION: occurs when two plate edges of DIFFERENT
DENSITIES COLLIDE; the DENSER PLATE will PLUNGE UNDER
THE LESS DENSE PLATE, AND BECOME MELTED IN THE
ASTHENOSPHERE – FORMING VOLCANIC MOUNTAINS OR
ISLANDS (Japan, Mt. St. Helens (The Cascade range))
***SUBDUCTION OCCURS WHEN ONE OR BOTH PLATE EDGES THAT COLLIDE
ARE OCEANIC PLATES (ocean plates have different densities and are always
denser than continental plates ***
***OCEANIC PLATES ARE ALWAYS SUBDUCTED UNDER CONTINENTAL PLATES
(they’re denser)***
***THE RING OF FIRE IS A SUBDUCTION ZONE FOUND AT
CONVERGENT PLATE BOUNDARIES. IT ENCIRCLES THE PACIFIC
OCEAN, AND IS THE WORLD’S MOST MAJOR EARTHQUAKE AND
VOLCANO ZONE (Indonesian tsunamis formed from earthquakes here)***
III. TRANSFORM BOUNDARIES
Are boundaries between two plates that are sliding past one another (side - side) :
FRICTION KEEPS THE PLATES LOCKED IN PLACE, AND PRESSURE BUILDS
BETWEEN THE PLATESWHEN THE PRESSURE BECOMES TOO GREAT, THE PLATES SUDDENLY
AND VIOLENTLY “RELEASE” - THEY MOVE PAST EACH OTHER, CREATING
AN EARHTQUAKE
***THE SAN ANDREAS FAULT IS PART OF A TRANSFORM PLATE BOUNDARY,
AND IS THE SOURCE OF MANY EARTHQUAKES***
PLATE BOUNDARIES DIAGRAMS
A. DIVERGENT BOUNDARY:
2 CONTINENTAL PLATES SEPARATE – RIFTING OCCURS:
RIFT VALLEY
CONTINENTAL PLATE
CONTINENTAL PLATE
MAGMA
B. DIVERGENT BOUNDARY:
2 OCEAN PLATES SEPARATE – SEAFLOOR SPREADING OCCURS:
RIDGE
RIFT
RIDGE
C. CONVERGENT BOUNDARY:
2 CONTINENTAL PLATES COLLIDE – FOLDING OCCURS
D. CONVERGENT BOUNDARY:
CONTINENTAL & OCEAN PLATES COLLIDE – SUBDUCTION OCCURS:
VOLCANIC
MOUNTAIN RANGE
Asthenosphere
E. CONVERGENT BOUNDARY:
2 OCEAN PLATES COLLIDE – SUBDUCTION OCCURS:
VOLCANIC
ISLAND ARC
F. TRANSFORM BOUNDARY:
2 PLATES SLIDE PAST EACH OTHER – TRANSLATION OCCURS:
FAULTS