Download Plate boundaries and Tectonic processes

Plate boundaries
and Tectonic
processes
THE MAJOR PLATES
Arrows show direction of plate motion
DIVERGENT BOUNDARIES:
PLATES MOVE APART: Seafloor spreading
• Creates ridge-rift systems and new seafloor
• MID ATLANTIC RIDGE and GREAT AFRICAN RIFT
VALLEY are examples
CONVERGENT BOUNDARIES
• PLATES MOVE TOGETHER & COLLIDE
• WHAT HAPPENS DEPENDS ON
DENSITY:
– Equal density – two continental plates –
FOLDING (mountains)
– Different densities – denser plate sinks –
SUBDUCTION:
• OCEAN – OCEAN PLATES : ISLAND ARCS
• OCEAN – CONT. PLATES: VOLCANIC ISLAND
CHAINS
CONVERGENT BOUNDARY–
2 CONTINENTAL PLATES: FOLDING
Since plates are of equal density – neither sinks –
both buckle upwards – process of FOLDING produces
FOLDED MOUNTAINS (Appalachians, Himalayas)
CONVERGENT - SUBDUCTION
Denser plate edge (oceanic) sinks into
asthenosphere, is melted, and creates VOLCANIC
MOUNTAIN RANGES (Cascades, Andes, Sierra Madres)
Ocean – ocean plate subduction
Older and denser plate edge (left) is subducted under
younger / less dense plate (right). This forms
VOLCANIC ISLAND ARCS (Aleutians, Japan, Indonesia)
TRANSFORM BOUNDARIES:
PROCESS OF TRANSLATION
“SIDE TO SIDE” MOTION – CREATES
FAULTS - EARTHQUAKES
THE MAJOR PLATES
Arrows show direction of plate motion
So, Divergence and Convergence
occur in balance
DIVERGENCE
CONVERGENCE
MAJOR EARTHQUAKE AND VOLCANO
ZONES EXPLAINED- They occur along
PLATE BOUNDARIES!
CONVERGENT - THE RING
OF FIRE - SUBDUCTION
DIVERGENT: MID-ATLANTIC
RIDGE – SEAFLOOR
SPREADING
HOT SPOTS – “Volcanic exceptions” –
occur in middle of plates
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Formation of the Hawaiian Islands