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Secondary 3 Geography > plate tecs gw 2 > Flashcards

plate tecs gw 2 Flashcards

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1
Q

how are fold mountains formed?

A
  • formed along convergent plate boundaries
  • compressional force creates immense pressure
  • layers of rock buckle and fold
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2
Q

what are some examples of fold mountains?

A
  • atlas mountain
  • swiss alps
  • andes
  • himalayas (tibet)
  • barisan
  • rocky mountains (NA plate)
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3
Q

name locations of fold mountains

A
  • convergent plate boundaries
  • himalayas: across southern asia (indian and erusian plate)
  • rocky mountains (juan de fuca and north american plate)
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4
Q

how are rift valleys formed?

A
  • valley with steep sides and flat floor
  • formed due to tensional forces
  • fault lines are formed
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5
Q

how are block mountains formed?

A
  • block of land with steep sides

- formed when sections of the crust extends along fault lines and rock masses

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6
Q

where are rift valleys and block mountains found?

A
  • divergent plate boundaries
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7
Q

what are the characteristics of volcanoes?

A
  • viscosity
  • low-silica
  • high-silica
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8
Q

define viscosity?

A

viscosity is the stickiness of lava/resistance to flow

like you compre pouring water to pouring chocolate sauce right chocolate sauce got higher viscosity

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9
Q

how does low-silica affect the volcano?

A
  • lower viscosity –> less explosive eruptions
  • allows gases to escape easily –> flows more easily through the vent by reaching surface
  • outer layer of the cooling lava forms a thin crust
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10
Q

how does high-silica affect the volcano?

A
  • higher viscosity –> more explosive eruptions
  • traps gases easily –> built up pressure below earth’s surface
  • magma rises through earth’s surfaces –> gases expand –> outward explosion
  • ejects: lava, ash, rock fragments and gases into the surrounding environment
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11
Q

what are the physical characteristics of shield volcanoes?

A
  • gently sloping sides

- broad summit

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12
Q

how are shield volcanoes formed?

A
  • formed when low silica lava (lsl) is ejected
  • lsl flows easily and spreads out over a large are before solidifying
  • lava doesn’t trap as much gas, not as explosive
  • base of volcano increases in size as lava accumulates
  • usually near divergent plate boundaries where magma can rise directly
  • i.e. mount washington in USA
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13
Q

how are stratovolcanoes formed?

A
  • develop from successive eruption of lava and pyroclastic
  • subsequent eruption ejects lava which covers pyroclastic and prevents it from eroding
  • successive eruptions build a high volcano with slightly concave profile
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14
Q

what are the physical characteristics of stratovolcanoes?

A
  • steeper at the top and gentler at the base; secondary cones may develop
  • mainly found at convergent plate boundaries
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15
Q

what is an active volcano?

A
  • currently erupting

- i.e. pacific ring of fire

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16
Q

what is a dormant volcano?

A
  • currently inactive but may erupt in future

- i.e. mount hood, oregon, USA

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17
Q

what is an extinct volcano?

A

volcanoes w/o seismic activity/geological evidence of eruption for past thousand years

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18
Q

what are the risks of living near volcanic areas?

A
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19
Q

what are the risks of living near volcanic areas?

A
  • massive destruction by volcanic areas

- pollution

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20
Q

explain massive destruction by volcanic materials

A
  • lava and pyroclast consists of ash, rock fragments, volcanic bombs
  • widespread damage to property
  • lava: has high temperature of 500-1400 degrees celsius and burns the area if it flows through
  • low-silica lava: moves rapidly and flows long distances; damage to larger areas
  • pyroclastic flow: destroys everything in its path with hot rock fragments at great speeds :( inhaling hot ash and gases can result to serious injury/death
  • volcanic bombs: fall in areas surrounding volcanoes and causes damage to property
  • landslides: have potential to obstruct flow of rivers; block roads, bury village and farmlands
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21
Q

name an example of massive destruction by volcanic materials

A
  • i.e. andes mountain, south america, 1985
  • pyroclastic flow
  • mixing of pyroclastic and glacial ice triggered laharas
  • engulfed the town and killed more than 20000 people
22
Q

explain pollution as a risk of living near volcanic areas

A
  • ash: disrupts human activities over large distances; thick plumes of ash settle on the ground; blocks sunlight; suffocates crops; severe respiratory problems to people and animals
  • gases: carbon dioxide; sulfur dioxide; hydrogen; carbon monoxide –> HARMFUL TO PEOPLE
23
Q

how is fertile soil a benefit of living near volcanoes?

A
  • lava and ash break down to form FERTILE volcanic soils
  • richest soils on earth
  • super favourable to agriculture
  • although rich in minerals, they are not available for planting when the rocks are not broken down (only avail. after 1000+ years)
24
Q

what is example of a area with fertile soil?

A
  • i.e. volcanic soils of java and bali in indonesia cultivate tea, coffee and rice
25
Q

how is precious stones and minerals a benefit of living near volcanoes?

A
  • can only be extracted from volcani areas after millions of years when upper layer of volcanic rocks are eroded
26
Q

example of an area for precious stones and minerals

A
  • i.e. diamond: cold volcanic rocks at kimberly, south africa; heated and pressured carbon; can be used for industrial tools and scientific research and jewellry
27
Q

how is tourism a benefit of living near a volcano?

A
  • hiking; camping; enjoy the scenery

- rich in history, can learn about the volcano

28
Q

what is an example of tourism?

A
  • i.e. ruins of pompeii italy
  • roman town buried by layers of ash from mount vesuvius in 79CE; unearthed to reveal building, pottery, mosaic, visited by almost 3 mil people every year
29
Q

how is geothermal energy a benefit of living near volcanoes?

A
  • derived from the heat in earth’s crust
  • grounwater in contact with hot rocks beneath surface –> heats up –> erupts as hot water/steam –> drive turbines and produce electricity
30
Q

what is an example of geothermal energy?

A
  • i.e. iceland’s electricity: 70% from geothermal power
31
Q

what are earthquakes?

A
  • vibration in the earth’s crust caused by sudden release of stored energy in rocks along fault lines
  • plate movements along plate boundaries
32
Q

how are earthquakes formed?

A

friction between moving plates –> slow build up of stress on rocks on sides of fault –> rocks can no longer withstand increasing stress (same) –> rocks suddenly slip many metres

33
Q

explain further the formation of earthquakes?

A
  • releases energy in the form of seismic waves
  • most of the energy released by EQ travels along surface of earth
  • stress from ground after EQ may cause aftershocks
  • series of aftershocks may occur for several months
34
Q

what are the characteristics of deep-focus EQ?

A
  • 70-700km below earth’s surface

- takes a longer time to reach surface has lost most energy by the time reached ES smaller impact on land

35
Q

what are the characteristics of shallow-focus EQ?

A
  • in upper 70km of earth’s crust

- seismic waves reach ES quickly greater impact on land

36
Q

what are the factors affecting the extent of an earthquake?

A
  • population density
  • level of prepardness
  • distance from epicentre
  • time of occurrence
  • type of soil
37
Q

how does population density affect the extent of an earthquake?

A
  • number of people living in affected area
  • more people, more affected
  • EQ in cities can cause more casualties and damage
38
Q

how does the level of prepardness affect the extent of an earthquake?

A
  • amount of preparation by authorities and citizens
  • evacuation plans. trained rescue workers, actions plans, drills
  • more prepared, fewer casualties, less chaos
39
Q

how does the distance from epicentre affect the extent of the earthquake?

A
  • closer to epicentre, more damage
  • i.e. christchurch, new zealand, 2011; epicentre in town a few km from city centre –> further from city centre had less damage –> city a lot of damage
40
Q

how does the time of occurence affect the extent of an earthquake?

A
  • at night –> people sleeping –> no time to evacuate –> more damage
41
Q

how does the type of soil affect the extent of an earthquake?

A
  • sediments loose and unconsolidated –> seismic waves amplified
  • structures built on saturated and unconsolidated sediments –> liquefaction
42
Q

where are most earthquakes located at?

A
  • can occur on convergent, divergent, transform
  • mostly @ convergent
  • 75% of pacific ring of fire
43
Q

what are the risk associated with living in earthquake zones?

A
  • tsunamis
  • disruption of services
  • landslides
  • destruction of property
  • desturction of infrastructure
  • loss of lives
44
Q

how are tsunamis formed?

A
  • formed by: movement of sea floor during large EQ; explosive underwater volcanic eruption; underwater landslide above sea level
45
Q

explain the formation of tsunamis in greater detail

A
  • seismic energy from offshore EQ forces out mass of seawater
  • tsunami waves may start at height of <1m, wavelengths of 100-150km, but pass undetected
  • point of impact on coast, tsunami waves could be travelling at 30-50km/h, may reach heights of 15m
  • sometimes sea recedes from coast before advancing offshore, minutes before the tsunami reaches above
  • can travel long distances and cuase widespread destruction @ coastal areas
46
Q

what is an example of a tsunami?

A
  • i.e. indian ocean , 9.2 EQ, 2004
  • triggered tsunami; waves spread throughout indian ocean
  • damage to coastal communities of 12 countries
47
Q

explain disruption of services as a risk of living in earthquake zones?

A
  • supply of electricity, gas, water
  • vibrations can snap pipes and break cables
  • cause fires
  • communication servies disrupted
48
Q

example of disruption of services?

A
  • i.e. kobe, japan, 1995: damaged pipes and transmissiom lines, disrupted gas and water, affected 1.4 million residents
49
Q

explain landslides as a risk of living near earthquake zones?

A
  • shaking of ground can weaken slopes of hills and mountains
  • unstable slopes –> landslides
  • rapid downslop movements of soil, rock, vegetation and debris
  • mudflow occur if there is heavy rainfall, saturating soil, mixed soilid debris flow down
50
Q

explain destruction of property as a risk of living near earthquake zones?

A
  • widespread destruction of homes
  • homelessness
  • can only reside in temporary shelters as homes are rebuilt
51
Q

explain destruction of infrastructure as a risk of living near earthquake zone?

A
  • EQ may cause cracks to forms in infrastructure
  • road and bridges damaged
  • affects transporation, unsafe to use damaged roads
  • takes longer for help to arrive, increased death toll

Secondary 3 Geography (8 decks)

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