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Geography > Tectonics > Flashcards

Tectonics Flashcards

1
Q

what is the lithosphere

A

upmost, solid, outer part of the earth - includes crust and upper portion of mantle

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2
Q

what is the asthenosphere

A

denser, weaker layer beneath the lithospheric mantle. rocks become semi-molten due to high temps and pressure

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3
Q

what is a volcanic hotspot

A

volcanoes that form in the middle of a plate due to hot magma plumes weakening the crust and eventually erupting

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4
Q

what is liquefaction

A

intense shaking during earthquakes causes loose sediment in the ground to lose strength and become more liquid than solid, meaning it loses its ability to support buildings/road foundations

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5
Q

evidence for Wegners theory of continental drift

A
  1. Jigsaw fit of continents and similar rock type and age - east of south america fits the west of Africa
  2. fossils of Mesosaurus found in both africa and south america - freshwater reptile, so couldnt have crossed the saline ocean.
    3.coal found beneath Antarctic ice cap - suggests it was once closer to the equator as coal only forms in warmer locations
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6
Q

what is slab pull

A

when a plate subducts, the plate sinking into the mantle is cooler and heavier than the mantle, meaning it pulls the rest of the plate down with it and causes it to subducts further.

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7
Q

what is the benioff zone

A

site of deep-focus earthquakes at the deepest point of the crust before the mantle, where the most friction and pressure build-up occurs

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8
Q

what is a composite volcano

A

-more explosive
-found at subduction zones
-have steep, cone-like shape
-low magma supply rate, so have infrequent eruptions

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9
Q

what is a shield volcano

A

-less explosive
-found at constructive boundaries and hotspots
-have broad, sloping shape
-high magma supply rate so have frequent (continuous) eruptions

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10
Q

what is a lahar

A

-secondary hazard from volcanoes
-mixture of rocks, mud and water which flow down a volcano (pyroclastic flow mixed w water eg. river)
-travel extremely fast and cause major destruction to all structures in their path

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11
Q

what is a jokulhlaup

A

-secondary hazard from volcanoes
-floods caused when (dormant) volcanoes erupt beneath glaciers or ice caps, creating huge volumes of meltwater containing ash and rock
-occur very suddenly and cause mass destruction and widespread landform modification

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12
Q

features of P-waves

A

-longitudinal so cause back and forth motion
-fastest waves - first to reach surface
-can travel through liquids AND solids
-least damaging

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13
Q

features of S-waves

A

-transverse so cause up and down shaking and sideways movement
-only travel through solids
-more damaging than P-waves
-slower than P-waves

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14
Q

what are L-waves

A

-love waves
-surface waves that cause side to side movement
-most damaging as energy is focused on surface
-slowest waves

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15
Q

features of the crust

A

-aka lithosphere
-uppermost layer
-thinnest and least dense
-made of continental crust (up to 70km thick, less dense, older) and oceanic crust (up to 7km thick, denser, younger)

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16
Q

features of the mantle

A

-aka asthenosphere
-up to 3000km thick
-temp gradient - rigid, cooler upper layer and semi-molten, warmer lower layer
-temp grad creates convection currents that contribute to plate movement

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17
Q

features of outer core

A

-liquid
-dense, semi-molten rocks containing Iron and Nickel
-movements generate magnetic field
-2200km thick

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18
Q

features of inner core

A

-solid
-iron and nickel
-compacted mass due to extreme pressure
-1250km thick
-extremely hot (5000-7000 degrees) due to leftover heat from earths formation and radioactive decay

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19
Q

Hess - development of plate tectonics theory

A

-sea floor spreading
-showed new oceanic crust is created by process of sea floor spreading at mid-ocean ridges widening by up to 5cm a year

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20
Q

Holmes - development of plate tectonics theory

A

-mantle convection
-hotter material near to the outer core moves upwards into the mantle. as it gets closer to the surface where it is cooler, it slows and moves outwards, forcing tectonic plates in diff directions
-direction of plate movements and type of plate margin determined by which was convection currents are flowing
-liquid rock then sinks back towards the core as it cools and the process repeats

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21
Q

global distribution of earthquakes

A

-majority close to or at plate boundary
-most powerful at destructive or conservative boundaries
-many around pacific ring of fire
-intra-plate earthquakes - happen in middle of plates/not at boundaries - often linked to hot spots

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21
Q

global distribution of volcanoes

A

-at or near plate boundaries - destructive and conservative plate boundaries
-volcanic activity high along west coast of n and s america and pacific ring of fire
-can also be found at hot spots in middle of plates eg Hawaii

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22
Q

global tsunami distribution

A

-majority around pacific ocean
-caused by tectonic activity at destructive boundaries
-waves larger than 5m occur along east coast of asia and west coast of both americas

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23
Q

what occurs at destructive plate boundaries

A

-denser oceanic crust subducts beneath the continental crust, leaving an ocean trench
-oceanic crust gets melted as it subducts further into the asthenosphere, and the extra magma created and organic matter on the sea floor causes pressure to build up.
-leads to pressurised magma being forced through weak areas in the cont. plate, forming composite volcanoes.
-causes earthquakes as friction during subduction causes pressure to build up, and when plates slip, pressure is released in form of an earthquake
-fold mountains occur when sediment is pushed upwards during subduction

24
Q

what occurs at constructive plate boundaries

A

-two plates pull apart and magma rises in the gap between, forming new land when it cools (sea floor spreading)
-forms shield volcanoes underwater and rift valleys on land

25
Q

what occurs at conservative plate boundaries

A

-parallel plates moving in opposite directions or same direction at diff speeds
-they can become stuck, causing pressure to build up until plates eventually slip and cause an earthquake
-no landforms as no land is destroyed

26
Q

what occurs at collision plate boundaries

A

-when two cont. plate boundaries meet as they move towards each other
-creates fold mountains eg Himilayas as the plates are of similar density, so neither can subduct
-means rocks are crumpled and forced upwards

27
Q

what are the primary hazards from volcanoes

A
  1. pyroclastic flow
  2. lava flow
  3. ash fall
28
Q

what are the secondary hazards from volcanoes

A
  1. lahars
  2. jokulhlaups
29
Q

what is a pyroclastic flow

A

-thick, dense cloud of gas, larger sediment and ash
-extremely hot (600 degrees) and fast travelling

30
Q

what is a primary hazard from earthquakes

A
  • crustal fracturing
  • when movement causes crust to crack, sometimes forming fault lines 1000km long
31
Q

what are secondary hazards from earthquakes

A
  1. liquefaction
  2. landslides and avalanches
    3.flooding (from tsunamis)
32
Q

tsunami formation

A

-when a large underwater earthquake occurs along subduction zones (at destructive boundaries), the sea floor can lift and displace the column of water above it
-forms a large wave that moves at fast speeds
-as the wave reaches the shore, a vacuum effect is created, causing the water to recede rapidly, exposing the seabed

-can also be caused by underwater landslides, volcanic eruptions and meteor strikes

33
Q

definition of hazard

A

events that have the potential to cause harm to life and property

34
Q

what does deggs model show

A

-how the overlap of natural hazards and vulnerability (in population) can cause a disaster

35
Q

factors affecting resilience

A
  1. building construction - are building codes enforced
  2. pop density
  3. level of urbanisation
  4. high quality infrastructure
  5. prepared healthcare system and emergency services
  6. public education
  7. level of corruption
36
Q

factors affecting level of impacts from a disaster and hazard vulnerability

A
  1. level of development in country/region
  2. insurance coverage - loss increased in HICs
  3. no. of ppl affected (pop density) and speed of economic recovery
  4. degree of urbanisation and value of land
  5. geographical isolation and inaccesibility
37
Q

def of actual risk + examples

A

-quantitative measure of risk
-eg. likelihood, impact and severity of risk

38
Q

def of perceived risk + examples

A

-qualitative judgment of risk
-eg. emotional/contextual factors, personal experience

39
Q

what is the risk-poverty nexus

A

-suggests poverty is both a contributing factor and consequence of natural hazards
-positive feedback loop - can cause further economic loss for already poor countries after hazard events

40
Q

what is governance

A

-way country is run on a local, regional and national level.
-strategies implemented can reduce risk and vulnerability of a country/region after a disaster

41
Q

what does good governance include

A
  1. meeting basic needs after disaster - food, water and health needs being met can reduce secondary hazards (eg. looting, disease)
  2. land-use planning
  3. preparedness eg. education and community preparation programmes (eg. Japan have national education days)
  4. no corruption of gov
42
Q

governance in Japan

A

-have annual earthquake education days - create community preparedness
-aseismic building designs and land-use zoning
-emergency warning systems
-gov work w insurance companies to ensure coverage for those who wouldnt normally be able to afford it

43
Q

what is a megadisaster

A

-high magnitude, high impact, infrequent disasters that affect multiple countries (directly or indirectly)

44
Q

Iceland megadisaster

A

-2010 volcanic eruption caused European airspace to close, causing over £1 billion in losses for tourism and airline companies
-African countries also couldnt import perishables so lost £65 million in goods

45
Q

Japan megadisaster

A

-2011 tsunami caused global economic impacts as disruptions to ports, factories and power supplies meant global car production chains and exportation of Boeing jets interrupted

46
Q

why is accurate data on hazards hard to gather

A

-immediate focus after disaster is on response, not data collection
-no single organisation is responsible for collecting data - all use diff methods
-difficult to gather in inaccessible, rural areas
-subject to political bias - eg. Western tourists were there during boxing day tsunami so media over-reported/exaggerated

47
Q

4 hazard management cycle stages (brief)

A
  1. mitigation
  2. preparedness
  3. response
  4. recovery
48
Q

volcano prediction tech

A

-thermal imaging - can detect temp increases
-seismometers - detect increased tectonic activity and tremors
-tiltmeters - detect ground swelling/deformation
-boreholes - test water levels
-gas detection - sulphur released when magma is near surface

49
Q

tsunami detection tech

A

-seismometers detect earthquakes and locate epicentre
-ocean monitoring tech eg. buoys, sensors on seabed can detect tsunami forming and send warnings

50
Q

disaster modification strategies (brief)

A
  1. land use zoning
  2. diverting lava flow
  3. GIS mapping
51
Q

what is land use zoning

A
  • planners regulate how land can be used (residential, commercial, industrial)
    -use hazard maps to identify areas most at risk, so wont build high value land in these areas
    -determine where structures that pose risk if damaged (eg. nuclear power stations) can be built
    -determine where structures critical to community (eg. hospitals) can be built
52
Q

what is diverting lava flow + challenges

A

-changing route lava is flowing away from communities by:
-digging channels or building barriers
-challenged: hard to predict which way lava will flow (so where to build/dig), terrain has to be suitable (downslope), may divert towards a diff community

53
Q

what is GIS mapping

A

-maps that help agencies identify areas that may be most affected and supply aid to them by combining info involving earthquakes (eg. epicentre, pop data, airports/hospitals, areas affected)

54
Q

Red Cross (NGO) role in managing loss after Pakistan earthquake

A

immediate:
-provided tents and blankets
-700,000 ppl provided w safe water

short term:
-more permanent shelters
-re-established water supplies
-re-built or rerouted roads closed by landslides

long term:
-provided seeds, tools, livestock and animal feed - provide their own food
-provided cooking kits and building supplies
-built new schools, medical centres and homes
-disaster risk reduction programmes developed

55
Q

role of insurers in managing loss

A

-can aid recovery as provide individuals and businesses w money needed for repair and rebuilding
-in some countries (eg. Japan), govs and insurance companies work together to provide coverage for those who wouldnt normally be able to afford it

56
Q

role of local communities in managing loss + example

A

-first to respond - immediate search and rescue (esp in rural/inaccessible/remote) areas that wouldnt receive aid as fast
-involved in long term strategies for rebuilding and resilience
-eg. Afghanistan - villagers in mountainous communities set up small search and rescue groups and travelled to more remote areas

57
Q
A

Geography (6 decks)

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