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

Since plates are of equal density – neither sinks –

both buckle upwards – process of FOLDING produces

FOLDED MOUNTAINS (Appalachians, Himalayas)

CONVERGENT BOUNDARY–

2 CONTINENTAL PLATES: FOLDING

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

CONVERGENCE DIVERGENCE

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

CLICK HERE TO VIEW ANIMATION

Formation of the Hawaiian Islands