Tectonics: The Plate Boundaries

Question 2

 How do mid ocean ridges occur

Answer 2

Manta rises, below surface,
pressures, lowered, decompression, melting
Rocks partially melt.
Plumes of magma, melt the crust above, crust expands on heating and up domes

split and volcanism begins convection currents in the way is the cost as a moves away from rift causes, lateral tension results in parallel faulting. Allow central section to subside into magma, creating a rift Valley

Question 3

How is a new ocean formed?

Answer 3

plates move further magma cools form basaltic ocean crust, causes, seafloor, spreading and ocean.
Basin gets wider as rift continues. Seawater floods in to create an incipient sea

Question 4

Evidence for seafloor spreading

Answer 4

Magnetic properties of the erupted basalt
earths magnetic field have been shown to flip occasionally so north and south pole swap
salts contains minute magnetic minerals and this changes directions depending on the earths magnetic field at the time of eruption 

Question 5

magnetic stripes

Answer 5

Polarity reversal from rock formations at the, mid-Atlantic ridge 

Question 6

Why do earthquakes occur at divergent plate boundary?

Answer 6

New Cross forms and spreads causes transform fault right angle two plate boundary
Move at different times. Friction causes plates to lock and buckle causing earthquakes. 

Question 7

How do volcanos form?

Answer 7

as plates move apart - decompression melting - magma rises and starts melting the crust - and forms a volcano - usually oceanic crust = basaltic lava = shield volc

but nubia and somalian - continental so andisitic lava

Question 8

descibe what a transformative / conservative plate is like

Answer 8

parallel movement of plates - differents speeds or/and directions - e.g. San Andreas Fault in Cali

Question 9

describe the san andreas fault

Answer 9

btw N. Americ ad Pacific
1300 km
right lateral strike slip fault
fault system visible and cause 10,000 earthquakes a yr

Question 10

why do earthquakes occur at conservatives

Answer 10

plates move sporadically and jerkily - frictional forces lock plates into eachotehr - friction builds up pressure strain and heat - suddenly releases energy - causes shallow focus earthquakes

Question 11

Plate movements in o + c convergence

Answer 11

Denser, oceanic subducts

Question 12

Tectonic processes in o + c convergent

Answer 12

Subduction and slab-pull
hydration melting
stoping (burning)
folding and faulting
friction and strain release

Question 13

Landform o + c convergence

Answer 13

Composite volcanoes, ocean, trenches, fold mountains, volcanic arcs 

Question 14

How do you trenches form - o + c convergence and example

Answer 14

As oceanic subducts, a deep V shaped depression is formed e.g. Mariana trench 

Question 15

How do earthquakes form o + c

Answer 15

Subduction is not smooth + friction friction = strain = builds up pressure which is released when the plate slips releasing seismic waves.

Question 16

What kind of earthquakes o+ c

Answer 16

Shallow to deep focus in the zone of earthquake foci - Wadatti-Benioff Zone

often high magnitude, 8 - 9 

Question 17

How do you fold mountains occur? E.g

Answer 17

As oceanic subducts said, sediment accumulate on ocean floor - scraped off and forced onto the continental plate, due to obduction - forms in accretionary wedge - adds to size of continent

Collision —> Crustal shortening leads to vertical thickness and reducing the width of the lithosphere collision zone. fold and faulting rocks form in the fold mountains

E.g. the Andes

Question 18

magma generation o + c

Answer 18

O subducts - when reach Benioff zone,
oceanic plate starts to crack and waters dragged out. This lowers the melting point of the magma (dehydration, melting) which generates magma.

Question 19

How are volcanoes formed o + c

Answer 19

Magma rises up to Fischers and freeze doping till they reach the surface. They melt some of the continental plates on its way up, making making it silica rich, causing andesitic lava. - this causes composite volcanoes

When explode cause release pyroclastic, flow, ash and gas 

Question 20

Describe andesitic lava

Answer 20

800 to 1000°C. High viscosity from is composite volcanoes. VEI 5-6

Question 21

How do you tsunamis occur?

Answer 21

Earthquake magnitude greater than six call seafloor to uplift causes a vertical displacement of water. This causes a tsunami. Low lying wave until close to
shore, it starts to grow into a taller wave.

Question 22

What happens in oceanic and oceanic convergence? E.g

Answer 22

Denser colder, oceanic plate subducts, this causes, submarine volcanoes, which, if grown, can cause volcanic arc. Lava can also produce island arcs.

E.g. Caribbean and South American plate

Question 23

Landforms in oceanic and oceanic convergence

Answer 23

Composite volcano, ocean, trench island arc



Question 24

Continental continental convergent

Answer 24

Two seas collide sediment exist between plates are pushed into each other and upwards, folding + faulting to make fold mountains

cause strain to build up when energy is released cause shallow, intermediate earthquakes, 6-8 magnitude 

Question 25

Example of continental continental convergent

Answer 25

Eurasian, and Indian plate forms the Himalayan mountains

Geosyncline (basin) was sea of Tethys which eventually subducted and filled with sediments which was obducted