plate tecs gw 2 Flashcards
1
Q
how are fold mountains formed?
A
- formed along convergent plate boundaries
- compressional force creates immense pressure
- layers of rock buckle and fold
2
Q
what are some examples of fold mountains?
A
- atlas mountain
- swiss alps
- andes
- himalayas (tibet)
- barisan
- rocky mountains (NA plate)
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)
4
Q
how are rift valleys formed?
A
- valley with steep sides and flat floor
- formed due to tensional forces
- fault lines are formed
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
6
Q
where are rift valleys and block mountains found?
A
- divergent plate boundaries
7
Q
what are the characteristics of volcanoes?
A
- viscosity
- low-silica
- high-silica
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
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
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
11
Q
what are the physical characteristics of shield volcanoes?
A
- gently sloping sides
- broad summit
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
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
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
15
Q
what is an active volcano?
A
- currently erupting
- i.e. pacific ring of fire
16
Q
what is a dormant volcano?
A
- currently inactive but may erupt in future
- i.e. mount hood, oregon, USA
17
Q
what is an extinct volcano?
A
volcanoes w/o seismic activity/geological evidence of eruption for past thousand years
18
Q
what are the risks of living near volcanic areas?
A
19
Q
what are the risks of living near volcanic areas?
A
- massive destruction by volcanic areas
- pollution
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
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
how is precious stones and minerals a benefit of living near volcanoes?
- can only be extracted from volcani areas after millions of years when upper layer of volcanic rocks are eroded
26
example of an area for precious stones and minerals
- 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
how is tourism a benefit of living near a volcano?
- hiking; camping; enjoy the scenery
| - rich in history, can learn about the volcano
28
what is an example of tourism?
- 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
how is geothermal energy a benefit of living near volcanoes?
- 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
what is an example of geothermal energy?
- i.e. iceland's electricity: 70% from geothermal power
31
what are earthquakes?
- vibration in the earth's crust caused by sudden release of stored energy in rocks along fault lines
- plate movements along plate boundaries
32
how are earthquakes formed?
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
explain further the formation of earthquakes?
- 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
what are the characteristics of deep-focus EQ?
- 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
what are the characteristics of shallow-focus EQ?
- in upper 70km of earth's crust
| - seismic waves reach ES quickly greater impact on land
36
what are the factors affecting the extent of an earthquake?
- population density
- level of prepardness
- distance from epicentre
- time of occurrence
- type of soil
37
how does population density affect the extent of an earthquake?
- number of people living in affected area
- more people, more affected
- EQ in cities can cause more casualties and damage
38
how does the level of prepardness affect the extent of an earthquake?
- amount of preparation by authorities and citizens
- evacuation plans. trained rescue workers, actions plans, drills
- more prepared, fewer casualties, less chaos
39
how does the distance from epicentre affect the extent of the earthquake?
- 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
how does the time of occurence affect the extent of an earthquake?
- at night --> people sleeping --> no time to evacuate --> more damage
41
how does the type of soil affect the extent of an earthquake?
- sediments loose and unconsolidated --> seismic waves amplified
- structures built on saturated and unconsolidated sediments --> liquefaction
42
where are most earthquakes located at?
- can occur on convergent, divergent, transform
- mostly @ convergent
- 75% of pacific ring of fire
43
what are the risk associated with living in earthquake zones?
- tsunamis
- disruption of services
- landslides
- destruction of property
- desturction of infrastructure
- loss of lives
44
how are tsunamis formed?
- formed by: movement of sea floor during large EQ; explosive underwater volcanic eruption; underwater landslide above sea level
45
explain the formation of tsunamis in greater detail
- 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
what is an example of a tsunami?
- i.e. indian ocean , 9.2 EQ, 2004
- triggered tsunami; waves spread throughout indian ocean
- damage to coastal communities of 12 countries
47
explain disruption of services as a risk of living in earthquake zones?
- supply of electricity, gas, water
- vibrations can snap pipes and break cables
- cause fires
- communication servies disrupted
48
example of disruption of services?
- i.e. kobe, japan, 1995: damaged pipes and transmissiom lines, disrupted gas and water, affected 1.4 million residents
49
explain landslides as a risk of living near earthquake zones?
- 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
explain destruction of property as a risk of living near earthquake zones?
- widespread destruction of homes
- homelessness
- can only reside in temporary shelters as homes are rebuilt
51
explain destruction of infrastructure as a risk of living near earthquake zone?
- 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
