Composition of the Earth

Earth LayersThe earth isn’t a solid sphereIt is made of 4 major layers- Crust- Mantle- Outer core- Inner core

Crust “outer skin”Continental crust is

about 70km thickOceanic crust is

about 10 km thick (this is why so much

ocean drilling occurs)

MantleAbout 2900 km thickMade of mostly Iron, Silicon and MagnesiumAsthenosphere is

the upper part of

the mantleVery viscous

Outer CoreApprox 2100 km thickMade of molten Iron and Nickel

Inner CoreApprox 1300 km

radiusSolid ball of Iron and

NickelExtremely hotStays a solid due to

very high pressure

Quick checkT/F – all layers are made of solid rockT/F – thickest layer is the mantleT/F – Inner core is made of liquid Iron

and nickelT/F – Outer core is made of silicon and

oxygen

AnswersF – all layers are made of solid rockT – thickest layer is the mantleF – Inner core is made of liquid Iron and

nickelF – Outer core is made of silicon and

oxygen

Plate MovementCaused by convection currents in the

mantle

DefinitionsTrench – steep walled valley where 2

plates meetSlab pull – plates subducting pulls the

rest of the plate with itRidge Push – new forming rock pushes

plate away from spreading centre

DefinitionsSpreading Centre – area where plates

move apart from each other

Rift Valley – a spreading centre that occurs on land

Types of Movement

Collisions at Plate BoundariesDivergent- Pulling apart

(spreading)- New rock is often

formed here

Collisions at Plate BoundariesConvergent- Plates come together- Often subduction occurs (one slides

under the other)

**More on this in a moment**

Collisions at Plate BoundariesTransform- Plates slide past each other- Produces earthquakes- Eg. San Andreas Fault

Convergent BoundariesThere are three different types of

convergent boundariesThese depend on what type of plates

come togetherOceanic-continentalOceanic-oceanicContinental-continental

Oceanic-ContinentalThe oceanic plate subducts beneath the

continental plateEg. Coastal BCThe Juan de Fuca (oceanic) plate

subducts under the North American (continental) plate

This causes coastal mountains and land volcanoes

Oceanic-OceanicOne plate will subduct beneath anotherVolcanic activity and possible islands

form

Continental-ContinentalPlates are not likely to subductThey push on each other and form

mountains