Plate Tectonics

Question 1

Evidence for continental drift

Answer 1

Jigsaw fit
Geological fit 
Tectonic fit 
Glacial deposits 
Fossil evidence

Question 2

Types of plate boundaries where volcanoes form

Answer 2

Oceanic oceanic divergent
Continental continental divergent
Oceanic oceanic convergent
Oceanic continental convergent

Question 3

Type of plate boundaries where ocean ridges form

Answer 3

Oceanic oceanic divergent

Question 4

Type of plate boundaries where ocean trenches form

Answer 4

Oceanic oceanic convergent

Oceanic continental convergent

Question 5

Type of plate boundaries where fold mountains form

Answer 5

Oceanic continental convergent

Continental continental convergent

Question 6

Type of plate boundaries where island arcs form

Answer 6

Oceanic oceanic convergent

Question 7

Type of plate boundaries where rift valleys form

Answer 7

Continental continental divergent

Question 8

Hydration melting

Answer 8

Destructive boundary (convergent)
Water forced down into mantle
Mantle melts at lower temp. As bonds in rock are disrupted my water molecule
Liquid mantle = magma which rises up through crust

Question 9

Decompression melting

Answer 9

Constructive boundary (divergent)
Lower pressure means lower melting point of mantle
Two plates move apart leading to an area of low pressure
Reduction in overlying pressure enable mantle to melt leading to upward movement of magma
No subduction because plate are same density

Question 10

Evidence for plate tectonics

Answer 10

Theory of Continental Drift 1915 (Alfred Wegener)

Mid oceanic ridges/Sea floor spreading 1962 (Harry Hess)

Paleomagnetism, symmetrical stripes 1963 (Vine and Matthews)

Hotspot theory 1963 and Transform Faults 1965 (John Tuzo Wilson)

Mantle Convection 1966 (Dan McKenzie)

Question 11

Types of magma and their characteristics

Answer 11

Basaltic: 45-55% silica, 1000-2000C temp, low viscosity, Low gas content

Andesitic: 55-65% silica, 800-1000C temp, medium viscosity, medium gas content

Rhyolitic: 65-75% silica, 650-800C temp, high viscosity, high gas content

Question 12

6 volcano types by shape

Answer 12

Flood/ Plateau Basalt / Fissure 
Shield
Cinder Cone 
Composite/ Stratovolcano 
Volcanic dome/ acid 
Caldera

Question 13

Primary volcanic hazards

Answer 13

Lava flows
Pyroclastic flows
Volcanic gases
Ash and tephra fall

Question 14

Secondary volcanic hazards

Answer 14

Lahars 
Volcanic landslides 
Tsunami 
Flooding 
Fires

Question 15

Focus

Answer 15

Location within Earth where underground rock moves and sends out earthquake waves

Question 16

Epicentre

Answer 16

Location on the surface of the earth directly above focus

Question 17

Earthquake waves/Seismic waves

Answer 17

Shock waves created at the focus and sent out in all directions

Question 18

Earthquake

Answer 18

Rapid vibration of earth created by a sudden movement of large sections of rock

Question 19

Seismograph

Answer 19

A device that reads earthquake waves

Question 20

Seismogram

Answer 20

The picture drawn by a seismograph indicating earthquake waves

Question 21

Natural causes of earthquakes

Answer 21

Plate boundaries
Intra plate movement
Isostatic recoil

Question 22

Quasi-natural / human induced causes of earthquakes

Answer 22

Fracking
Dams
Nuclear testing

Question 23

Two scales used to measure earthquakes

Answer 23

Richter scale - magnitude determined by logarithm of amplitude of waves recorded by seismograph

Mercalli scale - value assigned to a specific site after assessing damaged caused by an earthquake

Question 24

Two types of body waves and their characteristics

Answer 24

Body waves: travel through earth itself

P waves (primary): longitudinal waves, push and pull, fastest body wave, average speed 6km/s, travel through both solid and liquid

S waves (secondary): transverse waves, shake side to side, slower, average speed 4km/s, only travel through solid

Question 25

Two types of surface waves and their characteristics

Answer 25

Love waves: fastest surface wave, side to side, confined to surface of crust, only horizontal motion, shake ground at right angles to direction of movement Rayleigh waves: rolls along ground like a wave across the ocean, moves ground both up and down and side to side (horizontal and vertical), same direction of motion, most of shaking felt due to these waves

Question 26

Earthquake hazards

Answer 26

``` Landslides/ rockfalls Tsunamis Soil liquefaction Ground shaking Lateral spreading / ground displacement Fires ```

Question 27

Intrusive volcanic landforms

Answer 27

Batholiths Sills Dykes

Question 28

Extrusive volcanic landforms

Answer 28

Geyser Fumaroles Hot springs Mud pots

Question 29

Causes of tsunamis

Answer 29

Earthquake - Boxing Day 2004 Volcanic eruption - Krakatoa 1883 Underwater landslide - La Palma theory Impact of a meteorite

Question 30

Tsunami

Answer 30

Series of large ocean waves generated in a body of water by an impulsive disturbance that vertically displaces the water column

Question 31

Characteristics of tsunami

Answer 31

Shallow water waves Wavelength longer than depth of water travelling through Rate of waves energy loss inversely related to wavelength Shallow water, slow down, increased amplitude Deep ocean, long wavelength, low amplitude

Question 32

Boxing Day Tsunami causes

Answer 32

``` 26 Dec 2004 Eurasian and Indo-Australian plates Earthquake magnitude 9 240km off coast of Indonesia Speed 800km/h Open ocean less than 1m At shores 15m 20m uplift of sea floor along fault line Wave hit coast within 30mins of earthquake ```

Question 33

Impacts of Boxing Day Tsunami

Answer 33

250,000 people died - 14 different countries 8 people killed SA - 8000km away from epicentre 2 million made homeless Mangrove swamps acted as barrier to reduce energy Seismic waves caused damage to poorly built homes Sri Lanka train derailed killed 1000 people Tourism and fishing reliant countries Land disputes - lost documents

Question 34

Boxing Day Tsunami responses

Answer 34

Bodies buried in mass graves to prevent spread of diseases $7bn by gov't to help reconstruction Up to 5million people relocated into temporary refugee camps Building of homes took longer than expected due to lack of materials Transport routes hard to rebuild Short term aid e.g. Water purification tablets, medical supplies Early tsunami warning system in Indian Ocean installed for $20m