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
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)
3
Q
primary effects of earthquakes
A
- shaking
- destroyed infrastructure and habitats
- damaged agricultural land
4
Q
secondary effects of earthquakes
A
- tsunami
- soil liquefaction
- landslides
- flooding
- damn failure
- fire
- mass movements
- loss of crops
- landmarks lost
5
Q
earthquake impacts
A
- traffic
- homelessness
- injured
- hunger
- destroyed habitats
- destroyed economy
- damaged transport + communication
- lack clean water
- diseases spread
- looting
6
Q
soil liquefaction
A
- loose grains shake and lose cohesion: move further apart, act like a liquid: move unconsolidated and unpredictable
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
8
Q
disposal of liquid waste
A
- increased pressure destabilises rocks
- Oklahoma,3,2019
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
10
Q
underground nuclear testing
A
- P and S waves from explosion propagates through ground
- Korea, sept 3, 2017, 6.3
11
Q
increased crustal loading
A
- increased stress, rainfall, reservoir
- Atatük, 5.5, 2017
12
Q
stratocomposite volcanoes
A
- steep sides, cone shaped
- viscous, sticky lava
- layers of andesitic/rhyolitic magma
- explosive, gases
- convergent margins
13
Q
shield volcanoes
A
- eruption of fluid, runny lava
- travels further and forms thinner flows
- basaltic magma
- divergent margins
14
Q
Icelandic lava eruptions
A
- persistent fissure eruption
- large quantities of basaltic lava build up vast horizontal plains
- large scale: Colombia Plateau
15
Q
Hawaiian eruptions
A
- more noticeable central activity
- runny basaltic magma travels down slopes in flows
- occasional flows
- pyroclastic activity
- gases escape easily
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
