3.1 Plate tectonics

Describe the nature of the continental crust

35-70km thick

1500 m years old

Granite composition

Rich in silicon, aluminium

LESS DENSE, LIGHT COLOUR

list all the movements of tectonic plates:

Convection theory

Hotspot

Ridge push

Slap pull

Explain convection theory

radioactive decay in earths core produces heat.

Hot magma rises in convection currents

Cools at surface

Sinks as denser.

Explain convection theory

radioactive decay in earths core produces heat.

Hot magma rises in convection currents

Cools at surface

Sinks as denser.

Ridge push - explain:

magma intrusion at ocean spreading ridges, which propels the two plates apart.

Explain slab pull:

the force that the sinking (colder and denser oceanic crust) edge of the plate exerts on the rest of the plate. So gravity forces down

List all the types of plate boundaries and give a location

• oceanic constructive [Mid Atlantic ridge] N.American and Eurasian plate

• Continental constructive [Mid Atlantic Ridge]

• Oceanic/continental destructive [Nazca subduction under S.American plate]

• Oceanic destructive [japanese arcs- PACIFIC PLATE UNDER PHILIPINNES PLATE]

• Continental-continental convergent [The Himalayas - follows complete destruction of oceanic plate so continental converges with continental - neither subduct]

• Conservative [san andreas fault]

List all the types of plate boundaries and give a location

• oceanic constructive [Mid Atlantic ridge] N.American and Eurasian plate

• Continental constructive [Mid Atlantic Ridge]

• Oceanic/continental destructive [Nazca subduction under S.American plate]

• Oceanic destructive [japanese arcs- PACIFIC PLATE UNDER PHILIPINNES PLATE]

• Continental-continental convergent [The Himalayas - follows complete destruction of oceanic plate so continental converges with continental - neither subduct]

• Conservative [san andreas fault]

Explain how constructive boundaries form - oceanic (under the ocean)

Plates pull apart. / divergent as rising convection currents within mantle spread sideways forcing plates apart creating a rift. Through which molten basal comes to surface along fissure eruptions and through volcanoes. magma then cools and solidifies.

Transform fault: created at 90 degrees to ridge due to variations at which sea floor is spreading - get sheered apart.

example: N.American pull apart from Eurasian plate

explain how constructive/ divergent plat boundaries occur continental -continental (rift valley)

magma rises up and it pushes up the earth's crust → ridge created due to expansion or crust and pressure.

The land in middle (parallel fault lines) forced apart → rift valley

Volcanoes form where magma rises → graben

Example: MID ATLANTIC RIDGE

/destructive boundaries - oceanic-oceanic

1) more dense crust subduction under other crust or the one that’s moving faster

2) slab pull

3) forms oceanic trench + island arc/ chain of volcanoes

example: pacific plate subduction under phillipense plate

Japanese arc islands

Destructive plate boundaries - continental - oceanic

1) oceanic plate more dense subducts

2) Ridge push, slab pull and conventional drag

3) tension and sudden release of friction = earthquake

4) Sediment compress and uplift to form FOLD MOUNTAINS

Oceanic trench + volcanoes

EXAMPLE: NAZCA PLATE AND S.A PLATE

Fold mountains = the Andes

Convergent continental-continental

1) following destruction of oceanic crust

2) converge

Neither subducts and uplift

Himalayas mountains = fold mountains

Explain what happens at the conservative boundary

1) convection currents in mantel

2) parallel plates move in opposing direction or at different speeds

3) Pressure builds up

4) oceanic crust displace water

5) continental = fault index and earthquakes form sudden release of pressure after being stuck

EXAMPLE: San Andreas fault

Pacific plate moving NW

N.A plate moving NW but slower

Nature of oceanic plate

Denser

Older

Crust/Lithosphere

Outermost layer

Continental and Oceanic crust

Mantle/ asthenosphere

A layer of hot melted rock

Core

• inner core solid nickel

• Outer core molten lower density