Plate boundaries and Tectonic processes

Arrows show direction of plate motion 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

Arrows show direction of plate motion THE MAJOR PLATES Arrows show direction of plate motion

So, Divergence and Convergence occur in balance

MAJOR EARTHQUAKE AND VOLCANO ZONES EXPLAINED- They occur along PLATE BOUNDARIES! DIVERGENT: MID-ATLANTIC RIDGE – SEAFLOOR SPREADING CONVERGENT - THE RING OF FIRE - SUBDUCTION

Formation of the Hawaiian Islands HOT SPOTS – “Volcanic exceptions” – occur in middle of plates CLICK HERE TO VIEW ANIMATION Formation of the Hawaiian Islands