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Physical Geography (hazards) > Key Knowledge > Flashcards

Key Knowledge Flashcards

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1
Q

Hazard categorisation and examples

A
  • geophysical (landslides, avalanche, Lahar,mudflows , earthquake)
  • atmospheric (mudflows, flood, wildfire hazard, cyclonic storms)
  • hydrological (mudflows, avalanche, flood, cyclonic storms, wildfire hazard, tornado, lahar, tsunami)
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2
Q

Factors affecting hazard perception

A
  • cultural factors (perceived risk may differ due to experience)
  • economic factors (HIC= constantly educated, risk vs reward in LIC’s)
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3
Q

Fatalism

A
  • Some say hazards are ‘gods will’ losses are accepted as inevitable
  • people may remain where they are due to economic reasons
  • these people often have experienced hazards and lived through them
  • some may not be able to move
  • may be elderly and do not want to move
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4
Q

Adaptation/adjustment

A
  • when a town/city start to change their ways of living to fit natural disasters -> buildings could be tweaked with new designs
  • following the 2010 Christchurch earthquake the government have conducted a review of old buildings and retrofitted many of them with internal supports to minimise the chance of collapse in a future tectonic event
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5
Q

Prediction

A
  • knowing when and where a hazard will occur is hugely advantageous and can lead to improved chances of death toll, the way we can predict are:
    > seismic monitoring of areas around volcanos
    > measuring gas emissions from active volcanoes and considering concentrations
    > safelight observation of weather systems
    > geological ground changes as a precaution to an earthquake
    > odd animal behaviour
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6
Q

Mitigation

A
  • any action taken to reduce or eliminate the threat to property or human life as a result of a natural hazard -> this includes the ideas of adaptation and preparation but can also include anything done or an individual level to reduce the impact of a hazard upon an individual
  • any mitigation carried out needs to go through a cost benefit analysis to ensure that it is economically viable
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7
Q

Risk sharing

A
  • When a natural hazard event occurs somebody always loses out
  • risk sharing works on the principle that spreading the risk reduces any one group/individual’s risk, therefore making it more acceptable
  • may involve spreading the financial burden imposed by possible management or adaptation strategies so more elaborate and expensive ideas can e put in place
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8
Q

Management

A
  • the degree of. Management heavily depends on the wealth of a nation, for instance japan spend billions of pounds on its tsunami systems, whilst the Philippines relies on basic weather reports and wrapping belongings in cling film when typhoons hit
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9
Q

What does the park model look like

A
  • LOOKS LIKE: — and then a curved tick✅
  • stages from top down:
    > improvement
    > normality
    > deterioration
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10
Q

In the park model what are the phases

A
  • relief: immediate response focus on saving lives and properly search and care operation, urgent medical supplies, rescue equipment, clothing and food
  • rehabilitation: more complex than relief, may las several months efforts are made to restore physical and community structures at least temporarily
  • reconstruction/mitigation/preparedness: permanent changes are introduced to restore the quality of life and economic stability to the pre-disaster level or better. This can include mitigation and preparedness reducing vulnerability -> long term
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11
Q

The hazard management cycle

A
  • response
  • recovery
  • prevention/mitigation
  • preparedness
  • hazard event
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12
Q

The structure of the earth (inside - outside)

A
  • inner core
  • outer core
  • Mantle
    > asthenosphere: soft, plastic like rock in upper mantle just below the lithosphere
  • Crust
    >lithosphere: the solid top layer of crust in which plates are formed. Consists of crust and upper mantle
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13
Q

The earths heat

A
  • the hat inside earth moves continents, builds mountains and causes earthquakes
  • earth makes some of its own heat (keeps steady temperature)
  • earth has been losing heat since it formed, billions of years ago -> but its producing almost as much heat as its losing -> the process i which earth makes heat is called radioactive decay (many rocks in earths crust undergo it)
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14
Q

Continental crust facts

A
  • thickness: 30-70 km thick
  • age: about 2 billion years old
  • density: about 2.7 g/cm cubed
  • mineral content: (SIAL) silica, aluminium
  • rock type: granite
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15
Q

Oceanic crust facts

A
  • thickness: 6-12 km thick
  • age: 200 million years
  • density: an average of 3 g/cm cubed
  • mineral content: (SIMG) silica, magnesium
  • rock type: composed of SIMG or basalts
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16
Q

Plate boundary types

A
  • constructive
  • destructive
  • collision
  • conservative
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17
Q

Constructive plate boundary

A
  • 2 plates moving apart leaving a gap in the middle for magma to rise up through with force as the magma can escape easily
  • earthquakes occur
  • E.g. mid-Atlantic ridge rift valleys can also form as land falls into space left as plates move apart
  • volcanos, earthquakes, rift valleys
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18
Q

Destructive plate boundary

A
  • dense oceanic plate descends below less dense continental plate
  • as the plate descend it is melted due to friction with the continental plate, farming hot, liquid magma
  • this magma can then rise through cracks in the continental plate and form volcanos if it reaches the surface
    > (O&O) = earthquakes, ocean trench, volcanos
    > (O&C) = ocean trenches, fold mountains, volcanos, earthquakes
    > (C&C) = mountain ranges, earthquakes
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19
Q

Collision plate boundary

A
  • occurs when 2 plates of similar densities (e.g. 2 continental plates) move together
  • this causes the material between them to buckle and rise up, forming fold mountains
  • the Himalayas are an example of a chain of fold mountains. They have been formed by the African plate colliding into the Eurasian plate
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20
Q

Conservative plate boundary

A
  • exist where 2 plate do not directly collide but side past each other along a fault (weakness)
  • no volcanos are found along these plate boundaries, but earthquakes do occur
  • an example of such boundary is the San Andreas fault in California
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21
Q

Rift valleys (the creation of the African rift valley)

A
  1. Up warping of the crust takes place as magma rises as plates are driven apart -> tensional faults and cracks appear in the surface, allowing out gassing and steam eruptions
  2. Plates move apart as a rift valley is formed -> huge blocs of crust descend into the Mantle creating the valleys which deepen over time
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22
Q

Ocean ridges

A
  • plates moving apart
  • rising current in the mantle push solid surface layers up to form a ridge
  • currents pull surface layers apart. Faults form and central block falls
  • pressure in the mantle drops causing partial melting. This creates magma which rises up the faults to create new crust
  • process repeats
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23
Q

Benioff zone

A

The further the rock descends, the hotter the surroundings become. This together with the heat generated from friction, begins to melt oceanic plate into magma

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24
Q

Convection currents

A
  • LOOK: semi circle with arrows in direction of heat
  • occurs in the mantle
  • rising limb (less dense rock rises once heated) -> semi-molten rock spreads out carrying the above plate with it -> radioactive deca (cools & sinks back down to be reheated)
  • earths inner core is 5-7000 degrees celcius
25
Q

East African rift valley

A
  1. Elevated heat flow in the mantle caused a pair of thermal bulges in central Kenya md the afar region in Ethiopia
  2. As the bulges formed they stretched and fractured the crust into a series of faults
  3. Conventional currents in the asthenosphere cause the extension of the crust. As the crust extends grabens (down dropped blocks) and horsts (up thrown blocks) re formed
  4. As the rift continuous to extend parts of the crust become thin enough for oceanic type basalts to be erupted, signalling the formation of new oceanic crust
  5. Eventually the African plate will split in two, forming the Nubian plate and the Somalian plate -> this will create ocean ridges between them
26
Q

San Andreas fault cay

A
  1. It is the sliding boundary between the pacific plate and the NA plate. It slices California in two from cape Mendocino to the Mexican border. San Diego, LA and Big Sur are on the pacific plate. San Francisco and Sierra Nevada are on the NA plate -> despite San Francisco’s 1906 earthquake the San areas fault does not go through the city
  2. 3.5 million homes to be a risk with $289 million in reconstruction value. About 1800 people could die in. Hypothetical 7.8 mag quake
  3. It is actively monitored though an array of GPS instruments, accelerometer (measures vibration or acceleration of motion of a structure) ad seismographs
  4. Conservative plate margin involves 2 tectonic plates sliding past each other -> they do not pass smoothly, friction causes them to get stuck -> overtime pressure builds up until the friction is overcome which results in plates slipping. When the pressure is released it sends out huge amounts of energy causing an earthquake earthquakes along a plate margin can be very large -> aftershocks can be as dangerous as the earthquakes
27
Q

Shield volcanos

A
  • gentle slopes
  • frequent eruptions of basic lava
  • lava flows at high speeds and for long distances before cooling
  • usually non-violent eruptions
  • non-viscous lava due to basaltic composition
  • found at constructive boundaries
28
Q

Composite volcanos

A
  • steep sided with a distinctive cone shape
  • high with a narrow base
  • explosive eruptions of lava & ash
  • layers of alternating ash & lava
  • viscous lava builds in layers and does not flow far from the crater
  • found at destructive boundaries
  • secondary or parasitic cones formed when the main vent gets blocked
29
Q

Volcanic explosively index (VEI): forms of volcanic hazards

A
  • Lahars
  • mudflows
  • tephra
  • nuées Ardentes
  • lava flows
  • gases
  • acid rain
  • ash fallout
  • pyroclastic flows
30
Q

Plate tectonic theory

A
  • the lithosphere is broken up into large slabs of rock called tectonic plates
  • these plates move due to convection currents in the asthenosphere, which push and pull the plates in different directions
31
Q

Ridge push

A

The slope created when plates move apart has a gravity acting upon it as it is at a higher elevation. Gravity pushes the plats further away, widening the gap (as this movement is influenced by gravity, it is known as gravitational sliding)

32
Q

Slab pull

A

When a plate subducts, the plate sinking unit the mantle pulls the rest if the plate (slab) with it, causing further subduction

33
Q

Nuées Ardennes/pyroclastic flows

A
  • a hot chaotic mixture of rock fragments, gas and ash that travels rapidly away from a volcanic event (usually in the form of a cloud) -> leaves behind a deep layer of solidified lava and thick ash
  • Cause:
    > when the column of lava, ash and gases expel from a volcano and loses its upward momentum and falls back to the ground
    > another cause is when volcanic material expelled during an eruption immediately begins moving down the sides of volcanoes
    > they also form when a lava dome or lava flow becomes too steep and collapses
  • impacts after: floods, mudslides, power outages, drinking water contaminated , wildfires, homes destroyed and buried in ash, agricultural land is destroyed, death
34
Q

Lava flows

A
  • flow of magma down the surface of a volcano -> flows slowly first giving residents enough time to flee the surrounding area however lava is incredibly destructive, burying, crushing and burning everything in its path
  • lava flows can change depending on its viscosity. High silica contempt makes lava viscous, while higher temperatures and water content make it more fluid
  • 2 types of lava flow:
    > Aa flow: this is a few metres thick, a mix of uneven shaped, sharp edged ash and cinder blocks. It is unstable. Flows a distance of 0.5-10km. For example the Aa flow on Manual Loa volcano, 1984
    > Pahoehoe flow: is fluid rather than viscous, but does not move quickly. Often the surface layer is static whilst flow continues beneath. Flows a distance of 1-90km. For example the Pahoehoe flow on Kilauea volcano, Hawaii
  • lava flows pose a greater threat to property than human life due to opportunity for evacuation. Lava flows are more dangerous when released very quickly. They usually cause large but localised economic loses
35
Q

Gases (volcanic)

A
  • can be emitted before, during or after event; most dangerous gases involve: CO2, hydrogen chloride, hydrogen fluoride, hydrogen sulphide, sulphur dioxide
  • however the most abundant gas is water vapour but this doesn’t pose a threat to health. The concentration of different gases can vary considerably from one volcano to another
  • why are they hazardous: they cannot be seen, and due to being denser than ambient air, they can ‘pond’ in depressions around active volcanos. High concentrations can also pose health hazards in planes. Sulphur gases convert to sulphate aerosols and can pose health hazards in planes. Sulphur gases convert to sulphate aerosols and can cause short-term climate changes if they reach the stratosphere as they may remain there for years. Gases can also result in asphyxiation (which has caused nearly 2000 fatalities in the last two decades), respiratory diseases and skin burns as well as regional famine - which is an indirect hazard
36
Q

Mudflows

A
  • mudflow is a geologic phenomenon whereby a wet, viscous fluid made of fine to course grained material flows rapidly and turbulently
  • usually in a drainage way. Typically a torrential rainfall or very rapid snowmelt runoff is the initiating factor
  • mudflows develop when water rapidly accumulates in the ground and results in a surge of water - saturated rock, earth and debris
  • occur on steep flows where vegetation is not sufficient to prevent rapid erosion but can occur on gentle slopes if other conditions are met -> other factors are heavy precipitation in short periods and an easily erodible source material
  • can lead to: trauma, broken electricals, water, gas and sewage lines that result in injuries or illness
37
Q

Tephra

A
  • tephra is the general name given to anything thrown into the air during volcanic eruption. It can range from individual ash particles all the way to volcanic bombs. It is most common on stratovolcanoes
  • tephra layers are derived from explosive eruptions that inject particles (pyroclasts) to tropospheric and even stratospheric levels. The particles are carried upwards by an eruption column that consists of a lower gas-thrust region and an upper convective region
  • produces a wide range of hazard. When the ejected material is in the atmosphere it is electrically charged and often produces lightening. It can disrupt electricity, television, radio, and telephone communication lines; it can also bury roads and other man made structures, damage machinery, start fires and clog drainage and sewage systems
38
Q

Monitoring volcanoes: geological observations

A
  • measure the topography of a region + ground movements that occur around an active volcano
  • slope angle: a tiltmeter is used to measure changes of a volcanos side -> installed when volcano is relatively inactive (at 0 degrees) as magma rises into magma chamber the volcano as a whole expands
  • distance measurements: electronic measurements (EDM) are used to measure the horizontal movements -> GPS also used to measure horizontal change
39
Q

Monitoring volcanoes: seismic activity

A
  • earthquakes and tremors usually have low level seismic activity but an increase may signal a greater likelihood of an eruption. Also monitoring infra-sound -sub audible sound below 20Hz
40
Q

Monitoring volcanoes: gas emissions

A
  • as magma nears the surface and its pressure decreases, gases scape. Sulphur dioxide is one of the main components of volcanic gases, and increasing amounts of it shows the arrival of increasing amounts of magma near the surface. We measure these emissions either at the volcano (even in the crater by helicopter) or further afield at a safer distance, particularly in the run up to an eruption
41
Q

Protection/preparation

A
  • safety tips/ if eruption occurs in your area: stay away from active volcanos, keeps emergency kit, know your evacuation route, avoid rivers and low-lying regions
  • lava diversion: bombing lava tubes, robbing lava of an easy transport Chanel and exposing more of the lava to the air, slowing and cooling it further
  • cool it with water: slows flow of lava as water turns into vapour (only really works with slow moving lava)
  • build a barrier: slows the flow
  • add concrete: alters direction, slows flow
42
Q

Types of waves

A
  • p wave
  • S wave (ripple)
  • Rayleigh wave (slow moving up and down, propagate forward causing a rise and a fall)
  • love wave
43
Q

Mercalli scale

A
  • earthquake intensity scale measured 1-12
  • not used now as only measures damage so not very accurate
44
Q

Predicting earthquakes

A
  • past seismic events: we can predict through the time between major earthquakes and guess when the next one is going to happen
  • remote sensing: can provide spatially explicit and timely information of field changes in earthquake processes, motor surface temperature
  • radon gas emissions: released from cavities and cracks in ricks when they crack level of gas will go up, this can be detected
  • monitoring animal behaviour
45
Q

Liquefaction

A
  • The mixing of sand or soil and groundwater during shaking of a moderate or strong earthquake, when water&soil is mixed, the ground becomes very soft and acts similar to quicksand.
  • if liquefaction occurs under a building it may start to lean, tip over, or sink several feet. The ground firms up again after the earthquake has passed and the water has settled back down to its usual place deeper in the ground
46
Q

Landslides

A
  • land shaking due to earthquakes, destabilises cliffs and steep slopes, causing landslides and rockfalls as a significant side effect
  • heavy rain and unconsolidated or fractured rock are exacerbating factors
  • especially common in highland areas, many of which are fold mountains meaning they sit on unstable plate boundaries (Himalayas and the Andes)
  • further,ore, relief rainfall in these upland areas means the ground is significantly more likely to become saturated and therefore more likely to fail
47
Q

What causes a tsunami

A
  • tsunami is a large ocean wave that is caused by sudden motion on the ocean floor. This sudden motion could be an earthquake, a powerful volcanic eruption or an underwater landslide
  • subduction zones (friction and becomes stuck)
  • accumulated seismic energy (stuck plate continues to descend and pressure builds)
  • earthquake causes a tsunami
48
Q

Primary effects of tsunamis

A
  • ground shaking will cause: buildings to collapse, power lines to collapse, water mains, gas mains and sewers to fracture
  • immediate deaths&injuries from crushing, falling glass, fire and transport accidents
  • panic, fear and hunger
49
Q

Secondary effects of tsunamis

A
  • liquefaction of saturated soils
  • long term illness if disease not treated properly
  • power cuts restrict emergency services including immediate medical care
  • fires
  • civil disorder (looting)
50
Q

Long term effect of tsunamis

A
  • problems restoring trust in neighbours and civil authorities
  • long term ‘lost generation’ to develop local/regions economy
  • permanent disruption of natural drainage patterns. Loss of farmland and food production
  • higher unemployment as not all businesses recover from from damage
  • school, universities and infrastructure destroyed
  • expensive reconstructions
51
Q

Tropical storm formation

A
  1. Strong upward movement f air draws water vapour up from the warm ocean surface
  2. The evaporated air cools as it rises and condenses to form towering thunderstorm clouds
  3. Condensing air releases energy which powers the storm and draws up more water
  4. Several small thunderstorms combine to form a giant spinning storm. Surface winds exceed 120km/hour and a tropical storm is officially born
  5. Storm develop an eye where air rapidly descends. Most intense (strongest winds) are found in the eye wall on the edge of the eye
  6. Storm is carried across the warm ocean it continually gathers strength and energy
  7. Upon landfall the storms energy supply is cut off/ friction which the land slows and weakens it. If the storm reaches warm water again it may regain some strength again
52
Q

Coriolis effect

A
  • the coriolis effect is caused by the coriolis force which deflects objects within a rotating system
53
Q

Storm surges

A
  • usually 20ft tall
    -forms by change in the sea level- can lead to mass flooding (coastal)
  • the low presssure at the centre of the storm pulls the water levels up as there is low pressure on the ocean surface
  • another factor affecting storm surges is wind and prevailing wind direction
54
Q

Strong winds

A
  • causes: atmospheric pressure (rising and sinking of air in the atmosphere) (strongest in northern hemisphere)
  • risks: debris carried can collide with buildings, cars, people, or power lines, poorly built infrastructure
  • factors:
    > high sea temperatures
    > air density
    > the landscape that the wind hits
    > how high or low the wind flow is (surface = low due to friction)(altitude = wind speed high)
55
Q

Wildfire triangle

A
  • fuel (vegetation, anything combustible)
  • heat (sun, barbecue, cigs, lightening strikes)
  • oxygen
56
Q

The El Niño phenomenon

A
  • cause warmer than average temperatures and drier conditions, again reducing vegetation moisture content
  • El Niño is a climate cycle in the Pacific Ocean with a global impact on weather patterns -> begins when warm water in the western tropical pacific. Ocean shifts eastward along the equator toward the coast of SA (normally pools near Indonesia and Philippines). This is capable of leading to dry conditions and weather significantly hotter than average. Once lit strong winds can fan the flames of a wildfire and can lead to it spreading rapidly as well as burning with a more intense heat. These winds can also lead to faster drying of vegetation in the first place
57
Q

Dealing with wildfires

A
  • clear leaves and other debris from gutters, eaves, porches and decks
  • remove dead vegetation
  • remove flammable materials within 30ft of our home (propane, firewood stacks)
58
Q

What role can publicity/education campaigns play?

A
  • Smokey bear: ‘only YOU can prevent forest fires!’ (Slogan first in 1947)
  • spring 1950, in captain mountains of New Mexico, young bear cub found himself caught in a burning forest. He climbed a tree to survive, but he was still badly burned. The firefighters whop retrieved him were so moved by his bravery - they named him Smokey
  • he was put in the national zoo in Washington, D.C as the living symbol of Smokey bear, he played am important role in spreading messages of wildfire prevention and forest conservation
  • died in 1976
59
Q

Wildfire behaviour

A
  • heat transfer: radiation is the transfer of fire to an adjacent object by causing it to combust without touching it. Convection is similar to radiation but in an upward direction. Finally, conduction occurs when flames are in direct contact with another fuel source
  • 3 things effecting wildfire behaviour:
    > weather ( greatest influence, no control, sun, moisture, dynamic influence -> mostly wind)
    > topography (fire moves faster uphill)
    > fuel (anything that burn, different types different reactions, WE can influence)

Physical Geography (hazards) (8 decks)

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