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Geo: hazardous environments > 9.1 Hazards resulting from tectonic processes > Flashcards

9.1 Hazards resulting from tectonic processes Flashcards

1
Q

global distribution of plate boundaries

A
  • earthquakes: linear patterns largely associated with convergent plate boundaries where lots of pressure is released
  • volcanoes: linear patterns along plate boundaries, exceptions exist where there is a thinning of crust (hot spots), many along ring of fire i N Pacific
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2
Q

primary vs secondary waves

A
  • P: first felt, travel through all mediums, longitudinal (compressing and expanding)
  • S: can be more destructive, through solids only, transverse (right angled to direction)
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3
Q

primary effects of earthquakes

A
  • shaking
  • destroyed infrastructure and habitats
  • damaged agricultural land
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4
Q

secondary effects of earthquakes

A
  • tsunami
  • soil liquefaction
  • landslides
  • flooding
  • damn failure
  • fire
  • mass movements
  • loss of crops
  • landmarks lost
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5
Q

earthquake impacts

A
  • traffic
  • homelessness
  • injured
  • hunger
  • destroyed habitats
  • destroyed economy
  • damaged transport + communication
  • lack clean water
  • diseases spread
  • looting
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6
Q

soil liquefaction

A
  • loose grains shake and lose cohesion: move further apart, act like a liquid: move unconsolidated and unpredictable
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7
Q

factors affecting earthquake damage

A
  • strength + depth of earthquake
  • number of aftershocks
  • population density
  • time of day
  • distance from epicentre
  • secondary hazards
  • type of buildings
  • type of rocks and sediments
  • economic developmenet
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8
Q

disposal of liquid waste

A
  • increased pressure destabilises rocks
  • Oklahoma,3,2019
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9
Q

fracking

A
  • drilling wells, pumping in water and air to force out oil/gas
  • generates mini earthquakes
  • Gaoshan, China, 4.9, 12 injured, 2 dead
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10
Q

underground nuclear testing

A
  • P and S waves from explosion propagates through ground
  • Korea, sept 3, 2017, 6.3
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11
Q

increased crustal loading

A
  • increased stress, rainfall, reservoir
  • Atatük, 5.5, 2017
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12
Q

stratocomposite volcanoes

A
  • steep sides, cone shaped
  • viscous, sticky lava
  • layers of andesitic/rhyolitic magma
  • explosive, gases
  • convergent margins
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13
Q

shield volcanoes

A
  • eruption of fluid, runny lava
  • travels further and forms thinner flows
  • basaltic magma
  • divergent margins
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14
Q

Icelandic lava eruptions

A
  • persistent fissure eruption
  • large quantities of basaltic lava build up vast horizontal plains
  • large scale: Colombia Plateau
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15
Q

Hawaiian eruptions

A
  • more noticeable central activity
  • runny basaltic magma travels down slopes in flows
  • occasional flows
  • pyroclastic activity
  • gases escape easily
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16
Q

Strombolian eruptions

A
  • frequent gas explosions blast lava fragments of runny lava into air to form cones
  • explosive
  • large quantities of pyroclastic rock thrown out
  • commonly marked by white cloud of steam from crater
17
Q

Plinian eruption

A
  • powerful blast of gas pushing ash clouds high into the sky
  • lava flows more violent
  • ash falls: covers surrounded area
18
Q

Vulcanian eruption

A
  • violent gas explosions blast out plugs of sticky or cooled lava
  • very viscous lava solidifies rapidly
  • fragments build up colds ash and pumice
  • often clears a blocked vent and spews volcanic ash into atm
19
Q

Vesuvian/Plenean eruption

A
  • gas rushed up through sticky lava and blasts ash and fragments in huge explosion
  • gas clouds slopes
  • immense cloud of gas and volcanic debris several km thick
  • part may be blasted away
20
Q

Aa lava

A
  • rough and jagged
  • high viscosity
  • cools v quickly
  • breaking into chunks on surface
  • fast moving
21
Q

Pahoehoe lava

A
  • often smooth and ropey in appearance
  • slow moving
  • mostly unbroken surface
  • very hot even far from source
22
Q

gases and acid rain

A
  • sulfur dioxide, carbon dioxide, and hydrogen fluoride
  • Locally, sulfur dioxide gas can lead to acid rain and air pollution downwind from a volcano
23
Q

blocky lava

A
  • formed from rubble
  • stored in bubbles
  • smooth and viscous
24
Q

pillow lava

A
  • hot flaming lava erupts in seabed
  • slow bursts of lava give time to form small lobes when viscousity is low
  • mainly in mid-ocean ridges
25
Q

nuée ardente

A
  • highly destructive, fast moving
  • incandescent mass of gas-enveloped particles
  • turbulent, fast moving cloud of hot gas and ash erupted from a volcano
26
Q

pyroclastic flows

A
  • hot, above 800 C
  • mixture of rocks, gas an ash from vent
  • velocity exceeds 700 km/h
27
Q

lahars

A
  • destructive mudflow of pyroclastic material
  • flows down side of volcano along a channel
  • mixed with rainwater/rapid snow melt during eruption
  • up to 65km/h and 100 C
28
Q

landslides

A
  • side of volcano melt/collapse under saturation
  • magma releases gases that partially dissolve in groundwater
  • hot, acidic, hypothermal weakens rock
29
Q

tephra clouds

A
  • ash particles, unconsolidated pyroclastic material turn into gas
  • ice crystals
  • nearby water get elevated minerals damage
  • respiratory, eyes and skin
30
Q

ballistics

A
  • fragments of lava or rock ejected after explosive eruptions
  • substantial damage to infrastructure and environment (high T, E, Mass)
  • volcanic bomb: greater than 64 mm
31
Q

preparing for earthquakes

A
  • better forecasting and warning
  • improved building design and location
  • establish emergency procedures
32
Q

prediction and monitoring of earthquakes

A
  • small scale ground surface changes
  • small scale uplift or subsidence
  • ground tilt
  • seismic gap theory
  • changes in rock stress
  • micro activity
  • anomalies in the earths magnetic field
  • changes in radon gas cc
  • changes in electrical resistivity of rocks
33
Q

building design

A
  • soft storey at bottom
  • basement isolation: foundation on rubber allows ground to move
  • foundation built deep into underlying rocks
  • steel constructed frames
  • land use planning
  • vertical and spiral rods
  • suspension bridges
  • flexible pipes
  • less developed countries: light walls and gabbles, light roofs, small windows, reinforced walls, shock absorbers, confined masonry
34
Q

controlling earthquakes

A
  • altering fluid pressure deep underground at point of greatest stress
  • series of controlled nuclear explosions to release stress before critical levels
  • Paris 2018: highly pressurised water in the vicinity of earthquakes tends to limit its intensity
35
Q

San Andreas fault: 50 residents

A
  • strain meters measure deformation at a single point
  • two colour laser geometers measure the slightest movement between plates
  • magnetometers detect alterations in the earth’s magnetic field, caused by stress changes in the crust
36
Q

predicting volcanoes

A
  • since 1980, 19 correctly predicted of Mt St Helen’s 22
  • false alarm: 1976: 72000 evacuated in Guadeloupe
  • seismometers to record swarms of tiny earthquakes that occur as magma rises
  • chemical sensors measure increased sulfur levels
  • lasers detect physical swelling of volcano
  • ultrasounds to monitor low frequency waves in magma resulting from surge of gas in molten rock
  • risk maps
  • noticeable fumarolic activity: changes in composition and abundance of gases
  • hot or swelling ground surface
  • changes in gravity/magnetic fields or heat flows
37
Q

living with a volcano

A
  • some countries created by volcanic activity (Iceland)
  • soils are deep, rich, fertile
  • tourism
  • culturally symbolic
  • geothermal power
  • public preparedness: evacuation plans, during eruption keep car engine off, protect eyes, skin, close windows and blinds
  • evacuation centres, strong infrastructure logistics
  • info on TV/radio
  • drills, sirens
  • insurance
  • research into history of area
  • water and air quality after eruption
  • sandbags, water hoses
  • houses of titanium/tungsten stilts with triple reinforced roofs
  • full reliance on protection: false sense of security
  • 1973 lava flow in Iceland: sprayed water slowed flow
38
Q

perception of risk

A
  • important influence upon individual’s response
  • experience: the more adjustment
  • material wellbeing: more element of choice
  • personality: leader, follower, risk taker
  • do nothing and accept hazard/ adjust : identification, evaluation or risk and cost/leave

Geo: hazardous environments (6 decks)

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