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A2 Geography > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

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1
Q

Evidence for continental drift

A 
Jigsaw fit
Geological fit 
Tectonic fit 
Glacial deposits 
Fossil evidence
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2
Q

Types of plate boundaries where volcanoes form

A

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

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3
Q

Type of plate boundaries where ocean ridges form

A

Oceanic oceanic divergent

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4
Q

Type of plate boundaries where ocean trenches form

A

Oceanic oceanic convergent

Oceanic continental convergent

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5
Q

Type of plate boundaries where fold mountains form

A

Oceanic continental convergent

Continental continental convergent

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6
Q

Type of plate boundaries where island arcs form

A

Oceanic oceanic convergent

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7
Q

Type of plate boundaries where rift valleys form

A

Continental continental divergent

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8
Q

Hydration melting

A 
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
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9
Q

Decompression melting

A

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

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10
Q

Evidence for plate tectonics

A

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)

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11
Q

Types of magma and their characteristics

A

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

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12
Q

6 volcano types by shape

A 
Flood/ Plateau Basalt / Fissure 
Shield
Cinder Cone 
Composite/ Stratovolcano 
Volcanic dome/ acid 
Caldera
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13
Q

Primary volcanic hazards

A

Lava flows
Pyroclastic flows
Volcanic gases
Ash and tephra fall

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14
Q

Secondary volcanic hazards

A 
Lahars 
Volcanic landslides 
Tsunami 
Flooding 
Fires
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15
Q

Focus

A

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

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16
Q

Epicentre

A

Location on the surface of the earth directly above focus

17
Q

Earthquake waves/Seismic waves

A

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

18
Q

Earthquake

A

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

19
Q

Seismograph

A

A device that reads earthquake waves

20
Q

Seismogram

A

The picture drawn by a seismograph indicating earthquake waves

21
Q

Natural causes of earthquakes

A

Plate boundaries
Intra plate movement
Isostatic recoil

22
Q

Quasi-natural / human induced causes of earthquakes

A

Fracking
Dams
Nuclear testing

23
Q

Two scales used to measure earthquakes

A

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

24
Q

Two types of body waves and their characteristics

A

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

25
Q

Two types of surface waves and their characteristics

A

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

26
Q

Earthquake hazards

A 
Landslides/ rockfalls 
Tsunamis 
Soil liquefaction 
Ground shaking 
Lateral spreading / ground displacement 
Fires
27
Q

Intrusive volcanic landforms

A

Batholiths
Sills
Dykes

28
Q

Extrusive volcanic landforms

A

Geyser
Fumaroles
Hot springs
Mud pots

29
Q

Causes of tsunamis

A

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

30
Q

Tsunami

A

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

31
Q

Characteristics of tsunami

A

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

32
Q

Boxing Day Tsunami causes

A 
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
33
Q

Impacts of Boxing Day Tsunami

A

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

34
Q

Boxing Day Tsunami responses

A

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

A2 Geography (3 decks)

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