FRAMEWORK OF PLATE TECTONICS Plate is the lithosphere

FRAMEWORK OF PLATE TECTONICS Plate is the lithosphere ( that is solid, rigid and extend to 100 km on average ) and moves over asthenosphere. Plates are subdivided into 3 groups: Major (108 km 2 ) (7 plates) Intermediate (106 - 107 km 2 ) (6 plates) Small (<104 - 106 km 2 ) ( about 20 plates) Pacific Arabian Sinai–Palestine African Nazca Turkish – Adriatic Eurasian Philippine Juan de fuca North American Caribbean Iran South American Cocos Australian Scotia Antarctic

PLATE BOUNDARIES apart • Divergent Boundary – moving _____ (Oceanic Ridges). ( together (Subduction • Convergent Boundary – moving ____ Zones ( and Collisional Zones ). • Transform Fault Boundary – moving sideways past each other (Transform Zone). • Every boundary has its epicenters distribution, seismic and geologic characteristics.

Bands of seismicity— chiefly at trenches and oceanic ridges

Morphological and structural features Boundary Type Divergent Stress Tensional Oceanic-oceanic lithosphere Oceaniccontinental lithosphere • Mid-oceanic ridge • Volcanic activity Convergent Compressional • Oceanic trench • Volcanic island arc • Complex island arc • Collision zone Transform shear • Ridges & valleys. Continentalcontinental lithosphere • Rift valley • Volcanoes • Oceanic trench • Modified Cont. margin • Volcanic arc *Mountain belt. Mountain belts Fault zones

Measurement of plate motions 1. GPS Sites in California; hundreds of stations around the world

GPS Measured Motions using the Global Positioning System

Measured motions in Turkey

Izmit Earthquake (1999)

2. Hotspots: such as the one under Hawaii, have validated plate tectonic theory.

Why do the plates move? • Two related ideas are widely accepted: 1. Mantle convection: Hotter mantle material rises beneath divergent boundaries, cooler material sinks at subduction zones. 2. (Slab pull -ridge push). Slab pull: Denser, colder plate sinks at subduction zone, pulls rest of plate behind it. So: moving plates, EQs, & volcanic eruptions are due to Earth’s loss of internal heat.

How does convection work? No one knows —but they aren’t afraid to propose models! Whole-mantle convection Two mantle convection cells Complex convection