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Physical Geography > Tectonics and vulnerability > Flashcards

Tectonics and vulnerability Flashcards

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1
Q

Why is the core metal?

A

As the Earth cooled, denser materials like iron and nickel sank. It’s kept solid by the pressure of all the layers.

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2
Q

Description of constructive margin

A

-Core heats magma, rises to asthenosphere
-Cannot break through so moves parallel
-Plates are dragged apart
-Ridge push as plates are pushed up in the middle and their weight pushes them apart
-Slab pull where the other end of the plate is on a destructive margin
-Mid Atlantic ridge

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3
Q

Continental drift (pangea) and evidence for

A

Alfred Wegner 1915
-Jigsaw fit
-Geology that seems to be the same across continents
-Fossil evidence

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4
Q

Crust characteristics

A

400 C
Less dense
Granite & basalt
Solid

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5
Q

Mantle characteristics

A

870 C
Less to medium density
Upper=olivine Lower=magnesium silicate
Liquid & solid

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6
Q

Outer core characteristics

A

4400-6100 C
Dense
Iron & sulphur
Liquid

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7
Q

Inner core characteristics

A

7000 C
Very dense
Iron & Nickel
Solid

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8
Q

Effusive

A

Runny

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9
Q

Description of destructive margin

A

-Oceanic plate is subducted (slab pull)
-Fold mountains, as plate concertinas
-Melted rock & gas in subduction zone
-Great pressure so magma rises to make volcanoes, these are explosive
-Many shallow and deep EQs with benioff zone going deep
-Nazca and SA plates

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10
Q

Description of continental collision margin

A

-Neither subducts so no volcanoes
-Crumple upwards to make fold mountains
-EQs mainly on boundary and are very violent, also intra-plate as plates deform
-The Alps (African and Eurasian)

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11
Q

Description of transform margin

A

-Plates move parallel
-No subduction so no volcanoes
-Many shallow EQs
-Elastic rebound
-San Andreas Fault

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12
Q

Elastic rebound

A

Plates get stuck at the margin so start to bend. Snap back to original shape in new locations.

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13
Q

Formation of island chains

A

-Hotspot in oceanic plate
-Outpouring of basalt makes land
-Plate moves so creates island in new spot
-Hawaii

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14
Q

Causes of intra-plate EQs

A

-Old weaknesses from previous collisions
-Climate change causing isostatic rebound
(New Madrid fault line)
-Rising sea levels adding weight to crust

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15
Q

Viscosity

A

Low=runny High=thick
More silica = Higher viscosity

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16
Q

Basaltic lava

A

Low viscosity
Where lava is heated by core and low in gas
Low magnitude eruptions
Constructive margins

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17
Q

Effusive eruption

A

Lava runs down the volcano

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18
Q

Rhyolitic lava

A

High viscosity
Where subduction adds silica, gas and water to the magma
Magma has difficulty making it to the surface but creates very explosive eruptions when it does
Ash clouds, pyroclastic flows, volcanic bombs and lahars
Destrucive margins

19
Q

Earthquake terminology

A

Focus- Origin point
Epicentre- Point on surface above focus
Seismic waves- Transmit energy from eq

20
Q

EQ wave types

A

P - Compression, less damaging, fastest
S - Vertical amplitude, slower
L - Side to side, most damaging, at surface

21
Q

Liquefaction

A

Water saturated material becomes loose and water surrounds all grains.
Christchurch, New Zealand

22
Q

Primary impacts of a volcano

A

Lava flow
Pyroclastic flow
Gas eruptions
Ash cloud

23
Q

Secondary impacts of a volcano

A

Lahars
Landslides
Jokulhlaup
Acid rain

24
Q

Pyroclastic flow

A

Formed from collapse of eruption column; lava dome or lava flow. Fluidized by water vapour and gases. Montserrat 1997

25
Q

Lahar

A

A slurry of mud, water and volcanic debris, formed when a pyroclastic flow melts snow/ice or there is heavy rainfall

26
Q

What causes a tsunami (tsunamigenesis)

A

An impulsive and rapid crustal movement which displaces the water above it to create a series of waves

27
Q

Shoaling effect

A

As a wave/tsunami enters shallow water, the velocity diminishes and the height increases

28
Q

Natural hazard definition

A

An extreme event that has potential to cause loss of life and damage to property

29
Q

The pressure release model

A

Root causes
+Dynamic pressures
+Unsafe conditions
+Natural hazard
=Disaster

Risk = Hazard x Vulnerability

30
Q

Root causes

A

Limited access to: power, structures, resources.

Political & economic systems

31
Q

Dynamic pressures

A

Lack of: training, local investment, press freedom

Rapid population change/urbanisation

Deforestation

32
Q

Unsafe conditions

A

Physical environment

Local economy

Social relations

33
Q

Factors affecting perception of disasters/hazards

A

Common or rare event
Media coverage
Death toll
Location/timing
Education
Immediate or delayed impacts
Belief in authority

34
Q

Why has the number of disasters risen historically

A

-More people living in danger zones
-More hazards recorded by social media (but less reliable)
-Better monitoring (esp for LICs)
-Better understanding
-More priority of data collection

35
Q

Mount Nyiragongo

A

1977 Basaltic lava (very effusive) up to 60km/h, killing 50 and overwhelming villages

36
Q

Montserrat

A

1995 Pyro flow from collapsed lava dome, blanketing a nearby town. Typically 80km/h and can cover 10s-100s of km

37
Q

Pinatubo

A

1991 Ash column 19km high, gas release

38
Q

Eyjafjallaj

A

2010 Jokulhlaup and ash causing 20 countries to close their airspace

39
Q

Armero tragedy

A

1985 Lahar killed 22,000

40
Q

Mount St Helens

A

1980 Landslide covering 62km^2 and 600ft wave in Spirit Lake

41
Q

Nepal vulnerability

A

-Low GDP/high debt so lack of defence investment and ability to deal with secondary impacts
-Women don’t work
-Isolated communities in mountains
-Monsoons cause landslides
-Unequal education

42
Q

2015 Nepal EQ

A

-9000 killed
-$10bn damages
-180 buildings reduced to rubble in Kathmandu
-Landslides closed roads

43
Q

Japan

A

-2011 eq and tsunami
-15000 deaths
-fukushima damaged, 20km zone evacuated
-46000 buildings destroyed

Physical Geography (4 decks)

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