Tectnonics plate theory

lithosphere

the crust and the uppermost solid part of the mantle

tectonic plates

pieces of rock that make up the lithosphere containing either oceanic or continential crust

plate movement

The movement of tectonic plates relative to each other this results in the formation of landforms and tectonic phenomeno

Internal structure of the earth

core,mantle,crust

convection currents

currents of heat within the hot softened mantle below the crust, generated by the heat from the earth's core, drive tectonic plates movements

slab-pull force

gravitational force that causes a denser oceanic plate to sink further into the mantle under its own weight

divergent plate boundary

where plates move away from each other

convergent plate boundary

where plates move towards each other

transform plate boundary

where plates slide past each other

Plate techonic theory

plate movement result in the formation of landforms

How do convection currents lead to techonic plate movement

1: heat from the earth’s core causes the mantle material to become less dense

2: mantle material rises towards the surface

3:The rising mantle material then spreads beneath the plates and drag them apart, causing divergent plate movement

4:: The mantle material then loses heat and sinks towards the core

5: convergent plate movement occurs where the convection currents collide

6: the materials then get heated up again and the process repeats. This rising and sinking of the mantle material forms convection current

How does slab pull force contribute to the techonic plate movement

1:When 2 plates converge, the denser oceanic crust is pulled down by gravity as it subducts beneath the less dense crust

2: The denser oceanic crust sinks deeper into the mantle under its own weight, pulling the rest of the plate with it, contributing to further convergence

what is the evidence of seafloor spreading?

1: where 2 plates move away from each other at divergergent plate boundary, seafloor spreading occurs

2: magma from deep within the earth rise through the mid- oceanic ridge

3: new oceanic crust is formed

What evidence of seafloor spreading support the plate tectonic theory

• The age of rocks at the seabed shows a pattern( rocks nearly are younger and rocks further from ridge are progressively older)

• shows how new oceanic crust is created at divergent boundaries and then moves laterally on both sides of the mid oceanic ridge as the seafloor continues spreading

• as a result, oceanic crusts are usually younger than continential crusts

• proves that new crust is continually formed at the divergent boundaries at the mid oceanic ridges, and as the plates move, older crust is destroyed further away at oceanic trenches

Geographic north

the direction towards the fixed points on earth called the north pole

geographic south

the direction towards the fixed point on earth called south pole

magnetic north

direction that a compass needle points to which is the direction of the earths magnetic north pole where where the earth as a magnet itself

magnetic south

the dounth direction that a compass needle points to. theis is the direction of the earths magnetic south

normal polarity

when the earth’s magnetic north towards geographical northand magnetic south towards geographical south

reverse polarity

earth magnetic north towards geographic south and magneitc south towards geographic north

What is magnetic striping

• Earth has a geographic northand south as well as a magnetic north and south

• geographic north and south does not change

• but magnetic normal and south can shift

• right now, magnetic north is roughly around where geographic north is and magnetic south is roughly around where geographic south is- this is a normal polarity

• reverse polarity happens when magnetic normal is roughly towards geographically south and magnetic south is roughl;y towards geographically north

Magnetic striping occurs as

• basaltic rocks from the oceanic crust are volcanic rocks formed from iron-rich lava

• contain contain magnetic materials

• when iron rich lava erupts, it cools and solidifies

• its magnetic materials point towards the earths magnetic north,evident of earth polarity at the time

Why does evidence of magnetic striping surrport the plate tectonic theory

• Provides evidence that plates move, supporting the plate tectonic theory as

  • oceanic plates move away from each other

  • iron rich lava erupts from the centre of the ridge

  • lava cools, solidifies,and forms oceanic crusts

  • the crust is then pushed in both directions away from the ridge when lava erupts and solidifies as plates move apart

  • when when earth’s polarity reverses, the rocks record the reversals

  • overtime, as more lava moves away from the ridge due to plate divergence, a symmetrical zebra-like pattern forms

Volcano

landform created when the lava erupts onto the earth’s surface

rift valley

linear lowland region with steep sides

earthquakes

shaking of the ground due to the sudden release of energy when 2 plates suddenly slip past each other

fold mountain

mountains that are formed due to 2 coverging plates that cause the earth’s layer to fold

fault

a fracture along which the blocks of crust wither side have moved relative to one another

What are different tectonic plate boundaries

Divergent plate boundary

• oceanic-oceanic(eg north american and eurasion plate)

• continental-continental(eg nubrian plate and somalian plate)

Convergent plate boundary

• oceanic-oceanic(eg philippine plate and pacific plate)

• continential-continental( eurasion and indo-austrailian plate)

• oceanic-continental(eg nazca and the south american plate

Transform plate boundary

• Eg san andreas fault where pacific plate slides past the north american plate

What happens at the divergent plate boundary

tectonic plates move away from each other, resulting in mid-oceanic ridges,volcanos(submarine and islands),ridt systems and earthquakes

Oceanic-oceanic divergence

1:2 oceanic plates move apart

2: the decrease in overlying pressure causes parts of the underlying mantle to melt,forming magma

3; magma rises through the weak areas in the crust to the earth’s surface, and fills gaps caused by the spreading plates

How does it form the mid oceanic ridge and volcano?

• lava cools and solidifies to form the basaltic rocks

• the rocks makes up a new oceanic crust

• An extensive underwater mountain chain forms(mid oceanic ridge)

  • Oceaning north american plate and oceanic eurasion plate moves apart

  • this forms the mid atlantic ridge

• magma rises through the weak areas in the crust to the earth’s surface, forming submarine volcano

• after many eruptions the volcano may break the surface of the ocean and form volcanic islands such as in surtney,iceland

• earthquakes also occur as stress and tension released when plates move

continental-continental divergence

1: 2 continental plates move apart

2: rocks eventually fracture to form parallel faults

3: the rocks between these faults collapses to form a deep rift valley with steep sides

4: as the plates move apart, the decrease in overlying pressure causes parts of the underlying mantle to melt,forming magma.magma rises through the weak areas in the crust crust to the earth’s surface forming volcanos

how does it form volcanos and rift vallys

• earthquake occurs and stress and tension releases as plates move

• rift valleys are form

  • nubian plate pulls apart from the somalian plate forming the great rift valley

• volcanos are formed

  • eg mount kenya

What happens at convergent plate boundaries

tectonic plates are moving towards each other, reulting in fold mountains,volcanos including submarine volcanos, oceanic trenches and earthquakes.

• oceanic-oceanic

• continental-continental

• oceanic-continental

oceanic- oceanic convergence

1. 2 oceanic plates collide

2. the denser plate subducts beneath the other plate

3. this forms a oceanic trench(deep depression)

4. as the subducting plate sinks inot the mantle, water lowers the melting point of the overlying mantle, causing it to melt,forming magma

5. magma rises through the weak areas in the crust to the earth’s surface

6. this forms a chain of volcanoes, known as volcanic island

whats happens during the oceanic-oceanic convergence

• friction along subducting oceanic plate also causes earthquakes

  • guan an island near mariana trench experiences alot of earthquakes

• oceanic trenches and volcanic island

  • oceanic pacific plate subducts beneath oceanic philippine plate forming mariana trench as well as mariana islands

what happens during contenental-continental convergence

• friction along the convergent plate boundary cause earthquakes

  • himalayan mountain range experience many earthquakes

• magma doesnt rise to the surface so no volcano

  • continental indo-australian plate converges with the continental eurasion plate forming himalayan muntain range

oceanic-continental convergence

1. an oceanic plate collides with a continental plate

2. the denser oceanic plate subducts beneath the continental plate

3. This forms an oceanic trench in the subduction zone

4. as the subducting plate sinks into the mantle, high pressure forces forces out of its oceanic crust. water lowers the melting point of the overlying mantle,causing it to melt,forming magma

5. magma rises through weak areas in the crust to the earth’s surface, forming volcanoes on the continental plate

6. enormous pressure at this plate boundary causes rocks on the continental plate to be uplifted and buckled, forming fold mountains

what happens during oceanic-continental convergence

• forming of trench,folded mountain, volcano,

  • denser oceanic nazca plate subducts beneath the continental south american plate forming

    • Peru-chile trench

    • Andes fold mountain range

    • Nevado del ruiz volcano

• Earthquakes are formed

  • friction along the subducting oceanic plate causes earthquakes to occur which is common in the places above

transform plate boundaries

• tectonic plates slide past each other

• no crust is created or destroyed

• stress causes by plate movement produces a fault,a zone of fractures

• Earthquakes occur here as one plate suddenly slips past another

• magma does not rise to earth’s surface,hence no volcanos

  • Pacific plate sliding past the north american plate

  • forms san andreas fault

  • earthquakes are common