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Geography Edexcel A- level > Topic 1: Tectonic processes and hazards > Flashcards

Topic 1: Tectonic processes and hazards Flashcards

(52 cards)

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1
Q

How do tectonic plates move?
4 ways

A
  1. Convection currents
  2. Slab pull
  3. Ridge Push
  4. Subduction
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2
Q

How do convection currents move plates?

A

Heat from decay of radioactive elements heats lower mantle - causes magma to rise, which then cools and sinks.

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3
Q

How does slab pull move plates?

A

Weight of newly formed oceanic plates subducting pulls it under (causing subduction)

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4
Q

How does ridge push move plates?

A

Divergent plate boundaries - hot, less dense magma rises to surface in plumes - heats surface crust causing it to fracture, so molten magma can push through. Creates oceanic ridges which slide away from each other

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5
Q

How does subduction move plates?

A

Slab pull in subduction zone
More dense plate slides under the other - crust is being constantly formed and destroyed

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6
Q

Compare oceanic plates to continental:

A
  1. Oceanic is denser
  2. Oceanic is younger
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7
Q

What is palaeomagnetism and how does is prove that the seafloor is spreading?

A

Every 400,000 years, Earth’s polarity swaps (and cooling lava minerals align with polarity at the time.)
Same pattern of alternating magnetic direction on either side of oceanic ridges (suggesting new rock is being formed at the same time on either side)

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8
Q

What is a convergent plate boundary?

A

Collision Zone -
2 plates push against each other - form fold mountains

Subduction zone -
Denser plate subducts under less dense plate (plate melts and magma rises as plumes)

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9
Q

What is a divergent plate boundary?

A

Plates move apart
Magma is able to rise up through plates - forms new plates

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10
Q

What is a conservative plate boundary?

A

Plate is not destroyed or created
Plates slide past each other- friction creates build up of pressure which is released via earthquakes

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11
Q

When oceanic plate meets continental:

A

Oceanic plate is more dense so subducts under continental plate - plate melts and magma rises in plumes
Deep ocean trenches
Fold mountains
Earthquakes have deep focus

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12
Q

What is a Benioff zone?

A

Area where earthquakes occur

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13
Q

When oceanic meets oceanic:

A

Denser of faster plate is subjected beneath the other
Deep ocean trenches form
Underwater volcanoes
Earthquakes (Benioff zone) have deep focuses

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14
Q

When continental meets continental:

A

Collision margin forms
Sediments are crumpled and forced up to form fold mountains
Earthquakes are likely to have shallow focus

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15
Q

What events/ landforms occur at divergent plate boundaries?
4

A

Earthquakes
Volcanoes - shield
In oceans - Mid-ocean ridges form (magma from underwater volcanoes)
On land - Rift valleys (land between faults collapses to create a rift)

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16
Q

What events/ landforms occur at Conservative plate boundaries?
3

A

Strong, shallow focus earthquakes
e.g. San Andreas fault in California USA
Create hotspots - magma rises and volcanoes form, which is then carried away as the magma current moves and is replaced (Pacific ring of fire)
Intra-plate earthquakes - weakening of mantle caused by a new magma plume or large scale convection

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17
Q

What is a hotspot?

A

Form over extra-hot regions in mantle, where magma is more buoyant than surrounding rocks, so floats to surface and causes surface eruptions.

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18
Q

On average, how many people die each year due to earthquakes?

A

10,000 - but this number is HUGELY variable as one major event can completely skew statistics

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19
Q

How do earthquakes form?

A
  1. Pressure builds up from movement of plates against one another
  2. Suddenly released as seismic waves when rock fractures along cracks (faults)
  3. Point inside crust is called focus/ hypocentre
    Point on ground is called epicentre
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20
Q

What is more damaging for an earthquake to have?

A

Shallow hypo centre

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21
Q

What are the 3 seismic wave types?

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A

P waves - Fastest waves and travel through both solids and liquids (damaging)
S waves - Slower waves and only travel through solids (more damaging)
Love waves - Slowest but MOST damaging (surface waves)

22
Q

What is used to measure seismic waves?

23
Q

What motion are seismic waves travelling in?

Study These Flashcards
A

P wave - backwards and fowards
S wave - Right angles
Love wave - side to side

24
Q

Primary side effects of earthquakes
2

Study These Flashcards
A

1.Ground shaking - buildings, bridges, road sand infrastructure collapse
2.Crustal fracturing - earth’s crust cracks

25
Secondary side effects of earthquakes 4
1. Liquefaction - rocks become unstable and shaken turn into liquid (unstable for buildings) 2. Landslides - rockslides, mudslides and avalanches (account for a lot of death and damage) 3. Tsunami - underwater earthquakes 4. Aftershocks - occur in area of original earthquake (generally, larger earthquake = more and larger aftershocks)
26
Aftershock statistic
2011 6.3 magnitude earthquake struck Christchurch, New Zealand caused more damage than original 2010 one.
27
Statistic about volcanoes
1500 active volcanoes
28
Volcano primary hazards: 4
1. Lava flows - very hot (1170*) but move very slowly (minimal risk to humans but more to infrastructure) 2. Pyroclastic flows - dense hot rock, lava, ash and gases ejected from volcano (move very fast -100km per hour- and very hot - up to 700 degrees) 3. Tephra and ash falls - large pieces of rock cause injury or death whereas smaller ash travels far and can clog engines or cause roofs to collapse) 4. Gas eruptions - Sulphur dioxide causes acid rain
29
Volcano secondary hazards: 2
1. Lahars - masses of rock, mud and water that are too fast to outrun (caused by melting ice or heavy rainfall after an eruption) 2. Jokulhlaup - snow and ice in a glacier is melted by heat of a volcano (cause sudden and heavy floods that catch people unawares)
30
How do tsunamis form?
1 - displacement of a large volume e.g. due to an earthquake 2 - waves radiate from source in all directions 3 - wave height is small and fats wave speed 4 - as wave reaches shore, vacuum effect occurs 5 - wave slows and energy is used to increase wave height (up to 30m)
31
What impact can tsunamis have? 4
1. Can travel inland for several miles and sweep away buildings, trees and people 2. wash away soil - make infertile or salination can occur (becomes too salty) 3. completely change landscape - small islands washed away completely 5. spread of disease like cholera by contaminated water sources
32
Why are tsunami time travel maps useful?
Give an estimated time to evacuate by Help stakeholders plan and prepare for tsunami events Baes off of epicentre
33
When do hazards become disasters?
When they strike a vulnerable population that cannot cope using its own resources
34
What is risk equation?
(Hazard x vulnerability) / Capacity to cope
35
How might a developing country fair worse than a developed country? 3 ways
Higher number of deaths More reliance on international aid Slower economic recovery
36
Why might a developing country fair worse than a developed country? 5 reasons
1 Less access to education 2 Poor quality housing/ no specialised infrastructure 3 Worse healthcare 4 High population Density 5 Less accessibility - aid struggles to get there
37
What are the 3 progressions of vulnerability in the PAR model? Give an example for each
Root cause - Structures Dynamic pressure - Local investment Unsafe conditions - unprotected buildings and infrastructure
38
2023 Syria - Turkey earthquake - how were they geographically at risk?
1. 4 tectonic plates interact - one of world's most seismically active fault zones 2. Aid route was damaged after earthquake - delaying delivery of aid
39
2023 Syria - Turkey - how were they at risk politically?
1. On ongoing civil war has destabilised the country and its economy 2. Widespread political corruption
40
2023 Syria - Turkey - how were they at risk socially?
1. dealing with cholera outbreak when earthquake hit 2. over 2 million people already lived in temporary or unsafe shelter/ buildings
41
2023 Syria - Turkey - how were they at risk economically?
1. low income country 2. very few resources were dedicated to disaster prevention and preparation
42
What does PAR model stand for?
Pressure and Release
43
How are earthquakes measured?
Magnitude - - MMS - (goes from 1 - infinite but generally stops at 10) - scale is logarithmic Intensity - - Modified Mercalli Intensity scale - takes observations from people who experienced the earthquake - roman numeral scale (I to X)
44
How are volcanoes measured?
Eruptions - - Volcanic explosivity index - 0 to 8 - amount and height of volcanic material ejected, how long eruption lasts, qualitative description terms
45
Why are hazard profiled useful? 2
1. They can compare different or similar tectonic events 2. helps decision makers plan how to use resources depending severity of disaster
46
What are some hazard profile characteristics? 6
Magnitude Speed of onset Duration Areal extent Spatial predictability Frequency
47
What is one way in which hazard profiles are not useful?
Don't compare every aspect of a tectonic event
48
What is one statistic of tectonic event deaths and low income countries?
LI countries account for 10% of worlds population but 23% of world disaster deaths
49
Compare how LI countries are affected vs high income countries:
LI countries experience more deaths HI countries experience more economic losses - infrastructure is more expensive
50
What is World Risk Index?
Number is assigned to a country - higher number = higher disaster risk Allows for comparison of risk globally Looks at exposure, vulnerability, susceptibility etc
51
How can Governance affect natural disasters?
1. enforcing building regulations 2. quality of existing infrastructure 3. making preparedness plans 4. efficiency of emergency services 5. quality of communication systems 6. public education 7. level of corruption - what money is spent on
52
Haitit earthquake

Geography Edexcel A- level (4 decks)

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