tectonics

geography paper 1

hazard

a potential threat to human life and property - either hydro-meteorological hazards (caused by climate) or geophysical/tectonic hazards (caused by land processes)

tectonic hazards can occur due to:

• near plate boundaries - earthquakes + volcanoes

• intra-plate earthquakes - due to solid crust, which has weakened over time, cracking under pressure

• volcanic hotspots - unusually high temperature due to the up-welling of hot molten material from the earth’s core e.g. pacific ring of fire - has an unusually high temperature due to the magma rising as plume (hot rock)

tectonic trends since 1960

• number of recorded hazards - increased

• total fatalities - decreased - except mega disasters

• number of people affected - increased (population growth)

• economic costs - increased due to better infrastructure development + increasing insurance/repairs cost

why is reporting disaster impacts difficult?

• do you only consider direct deaths or also indirect deaths - such as spread of disease, days after the impact?

• location - isolated areas + areas with a high population density may be hard to collect information from

• differing methods of collection

• number can be subject to bias - e.g. burmese government claimed 0 deaths during the 2004 boxing day tsunami - false

tectonic theory

• crust/lithosphere - oceanic crust - 7km thick + continental crust - up to 70km thick

• mantle/asthenosphere - mainly made up of silicate rocks - rich in iron and magnesium. the mantle is semi-molten + has a temperature gradient - resulting in convection currents 700-2890km below crust

• outer core - semi-molten + dense - contains iron + nickel alloy, 2890-5150 km below crust

• inner core - solid due to extreme pressure + high temperature (result of primordial heat left from earth’s formation + radiogenic heat from radioactive decay)

case study: montserrat/soufriere hills (1995-1999) - volcanic eruptions

was in constant eruption since dormancy (before 1995) - 2/3 population have left since then.

• 1995 - eruption of ash/steam up to 40,000 feet - lead to temporary flight ban, surge cloud of 100mph ash, 500 evacuated - was 1/3 of the population

• 1996 - south destroyed by pyroclastic flows + tephra which covered 1/2 of the island, so the remaining residents went into temporary shelter

• 1997 - 19 killed by pyroclastic flow due to poor management + the only airport was destroyed making aid difficult to receive - only available by sea

• 1998 - continued eruptions every 9 hours - environment suffers as ecosystems were suffocated by toxic gas + tephra

• 1999 - volcanic activity finally calms, but montserrat in total destruction as 17 settlements, major roads and airport destroyed

• 2025 - focusing on geothermal energy, sand-mining + tourism to continue rebuilding in “ash to cash” scheme

AID:

• UK government set up modern tracking + seismology stations + pledged £41 million for survivors

• £10 million - direct aid to help response of navy

• however, there were riots/protests among population as “government was not engaged enough in what locals saw as the decimation of their island” - led to chief minister resigning due to allegations of being too “pro-british”

• HMS liverpool evacuated over 7000 residents to neighboring islands e.g. antigua + barbuda

• british government enacted a scheme that allowed citizens from montserrat to claim residence in uk

case study: boxing day tsunami - mega-disaster

9.0 magnitude earthquake under the ocean + pressure buildup of 2 oceanic plates = significant impacts across indian ocean:

• landscape impacts: smaller islands, fishing villages + coastal infrastructure destroyed. communications + electricity power lines cut, roads + rail destroyed. fires broke out due to severed water pipes. water too fast + strong to swim against + coastal ecosystems (mangroves + coral reefs) destroyed + polluted by waste

• population impacts: estimated 250,000 killed, outbreak of disease e.g. cholera due to lack of freshwater supplies. lack of food as fish died + farms destroyed. thousands made homeless, as well as many losing jobs (thailand’s tourist hotels + fishing vessels destroyed).

RESPONSE:

• immediate response: fresh water, water purification tablets, food, sheets + tents provided. medical teams + forensic scientists arrived. uk government promised £75million + uk public donations of £100million followed

• long-term response: 2005 - £372million donated by uk public but only £128million spent by disasters emergency committee - on rebuilding. spent £40million on sri lanka + indonesia, £190million on building 20,000 houses. 2006 - set up the Indian Ocean Tsunami Warning System, educating citizens + local authorities on how to act for future events - but many suffer from PTSReactivity due to loss of family members

case study: eyjafjallajokull 2010 - volcanic eruption

• local impacts: 700+ locals evacuated, communications + transport disrupted - cost £12million to reconstruct, affected tourism, years worth of crops damaged = food shortages

• international impacts: 48% of air traffic grounded for 8 days across europe, due to ash (water + silica) = lack of imported parts + materials impacted industry (apple - japan, nissan - uk). fresh produce couldn’t be imported (kenya suffered - 3000 tonnes of flowers destroyed - meant for international trade). many stranded worldwide. total losses (for airline industry) were around £1.1 billion - due to grounded flights.

RESPONSES:

• regularly updated information sent from the icelandic meteorological centre to affected locals, airlines, persons of influences, governments etc. - to continue spread of info + coordinated responses

• government rebuilt destroyed roads + infrastructure in under 2 months

• redcross offered supplies + resources to affected individuals

icelandic tourism industry has exponentially grown since 2010 - partly due increased awareness of its natural beauty + attraction - due to coverage of event + environment has since grown back more fertile than ever (ash deposits). GDP + social recovery in iceland beyond stage 5 of the park model.

fracture zones

oceanic: belt of activity through the oceans, along oceanic ridges through africa, red sea, dead sea

continental: belt of activity through mountain ranges, across spain, alps, middle east, himalayas,

convection currents (only occurs in the asthenosphere)

• heat from the inner core convects through mantle into asthenosphere

• hot magma rises from outer core as it becomes less dense with heat

• magma is cooler at the top of the mantle (further away from heat sources) - becomes more dense + sinks to the bottom

• cooler magma is reheated + begins to rise again = convection current (loop)

crust

• oceanic - thin, new, high density of rock, mainly basalt

• continental - thick, old, low density of rock, mainly granite

denser plate subducts while the other is forced upwards

constructive plate boundaries ← →

• oceanic + oceanic - magma rises in the gap left, forming new land = SEAFLOOR SPREADING - proves plate movement. as magma rises, less explosive underwater volcanoes are formed + ocean ridges. e.g. mid-atlantic ridge

• continental + continental - any land caught in the separation forced apart = RIFT VALLEY (volcanoes forming where magma rises in the gap) this gap eventually fills with water + separates from main island. lifted areas = horst, valley = graben e.g. african rift valley

destructive plate boundaries → ←

• oceanic + oceanic - heavier oceanic plate subducts, creating OCEAN TRENCHES, built up pressure leads to underwater volcanoes - bursting through the plate. this lava cools, forming ISLAND ARCS. e.g. alaska

• continental + oceanic - denser oceanic plate subducts = deep OCEAN TRENCH, oceanic crust melts as it subducts into asthenosphere. extra magma, pressure builds forcing magma through weak areas. explosive, high pressure volcanoes erupt through the continental plate = COMPOSITE VOLCANOES. FOLD MOUNTAINS occur when sediment is pushed upwards during subduction e.g. andes

• continental + continental - plates aren’t dense like oceanic, so pressure builds + no subduction occurs = pile up of continental crust on top of lithosphere = forming fold mountains e.g. himilayas, alps

conservative plate boundaries ↗↗ or ↗↙

no plates destroyed so no landforms are created. when plates move = pressure builds → oceanic crust displaces water + continental crust creates faultlines where movement occurs = earthquakes

examples include san francisco, san andreas fault

what proves plate movement?

seafloor spreading (magma rising between the gaps made by 2 oceanic, constructive plate boundaries) = as new rock forms + cools. the magnetic grains in the rock align with the poles (N+S) + switch periodically. when they switch, new rocks align opposite to the old rock - found by geologists.

ridge push

slope created when gravity acts on constructive plates at a higher elevation. gravity pushes plates further away, widening the gap = GRAVITATIONAL SLIDING

slap pull

when a plate subducts, the plate (older + denser) sinking into the mantle pulls the rest of the plate with it = causing further subduction

mechanisms that could cause plate movement

• mantle convection - radioactive elements (from earth’s core) decay, producing thermal energy + convection currents

• slap pull

however, tectonic movement isn’t fully understood - previously convection currents considered the primary cause, now slap pull is

key points of earthquakes

• plates don’t fit perfectly - motions are not fluid so at all boundaries plates can become stuck due to friction

• when these plates get stuck, convection currents in the mantle continue to push, building pressure = eventually, plates give way + released with sudden movement = JOLTING MOTION = seismic movement + shockwaves

• focus/hypocentre is where earthquakes originates from - epicentre is directly above this

• intensity decreases as you move further from the epicentre as waves lose energy, however impacts felt/damage will still vary

seismic waves - primary

• travels through solids + liquids

• compressional - waves vibrate in the direction in which they travel

• vibrates in the direction of movement

• travels at 4-8 km/s

• shakes backwards + forwards, and through the interior of the earth alongside secondary

seismic waves - secondary

• cannot travel through liquids

• vibrate perpendicular to direction of travel

• travels at 2.5-4 km/hr

• one of the most destructive due to its large amplitude

seismic waves - love

• near to ground surface

• rolling motion - producing vertical ground movement + side to side

• travels at 2-6km/hr

• one of the most destructive due to its large amplitude

seismic waves - raleigh

• vertical + horizontal displacement

• travels 1-5 km/hr

• compressional - waves vibrate in the direction in which they travel

case study: tohoku 2011 (9.1) - mega-disaster

context: japan is a highly developed with advanced tech, infrastructure + thriving economy + a mutli-hazard zone. main cause was due to friction built up on a destructive plate margin = megathrust earthquake

• primary impacts: groundshaking (damage to buildings) + landfall (beachfront dropped by >50cm)

• secondary impacts: tsunami, 16,000 reported dead, power plant damage, $235 billion lost, 340,000 displaced, 300 hospitals damaged + roads/trains destroyed

• immediate response: warned about tsunami 3 mins post earthquake, scientists PREDICTED, search + rescue workers + 100,000 japanese self defense force dispatched within hours + sniffer dogs. international aid, evacuation zone was declared around the damaged powerplant - those nearby given iodine to reduce radiation risk = PROTECTION. restricted access to muddy/debris areas + many checked for radiation levels

• long-term responses: budget of £190 billion to recover over 10 years, coastal protection, prioritised rebuilding + improving the economy, restored all water + electricity - end of 2011.

were they prepared? yes, with aseismic building codes, early warning systems, and education + drills for schools, offices + public areas = saved lives + reduced damages

why did they struggle? large elderly population - so slower at running/swimming/evacuating, with many “set in their ways” and unprepared for tsunami + the nuclear crisis

case study: kiribati - sea level rising

context: in danger of becoming uninhabitable due to climate change - requiring global solutions to fix (have joined Paris Agreement + COP26). LIC (average citizen makes £3000 a year) - can’t fund projects. highest point is only 81m above sea level. 110,000 residents about to become climate refugees - primarily to new zealand, but first to the capital tarawa.

challenges they face:

• global warming = sea level rising as glaciers melt, severe coral bleaching due to ^ = damage to delicate biodiversity,

• warmer oceans lead to violent + regular tropical storms = socioenvironmental consequences + hinders further development.

• mass migration to south tarawa = overpopulation, spread of disease, pollution + poor sanitation

• deforestation of coastal mangroves increases vulnerability BUT allows fishing.

• locals rely on subsistence farming - so both incomes + livelihoods destroyed.

how are they managing? they are evacuating, local government are dredging islands + considering elevated roads to adapt to flooding + accessibility

now, kiribati has become allies with china to help develop + manage climate change - using chinese funding to build large-scale infrastructure e.g.the elevated roads to work against sea level. however, some argue they may fall into “debt traps”, unable to pay off loans - giving up kiribati’s control 3.5 million km of ocean.

waves

as all waves move at differing speeds, they hit a location at different times - felt by survivors like aftershocks.

secondary hazards of earthquakes

• soil liquefaction - impacts poorly compacted sand + silt as moisture separates from soil + rises as water to surface = soil behaves like a liquid = building subsidence + gradual sinking. e.g. japan 2011, christchurch 2010

• landslides - earthquakes’ shaking can weaken or damage cliff faces, hills + snow = unconsolidated material collapses. landslides can travel several miles + accumulate material on the way. risk varies with topography, land use, soil, rainfall. e.g. haiti 2010, nepal

• tsunamis - ocean crust jolted during earthquakes = water is displaced upwards + pulled back down by gravity = energy transfers to water + travels through like a wave. water travels fast with a low amplitude, as it reaches the coast, sea level decreases so friction between seabed + waves = waves slow down while gaining height creating a wall of water (average 10ft - can reach 100ft). usually found in subduction zones at a destructive plate margin + felt most by asia + australia. e.g. boxing day tsunami 2004, tohoku

• shockwaves - low level earthquakes follow e.g. japan 2011, haiti

primary hazards of volcanoes - all fast speed of onset

• lava flows - streams of lava erupt onto earth’s surface - can be fast flowing = dangerous (based on viscosity) e.g. hawaii, DRC

• pyroclastic flows - mix of hot dense rock, lava, ash, gases = move very quickly across surface, high speed = dangerous + can cause asphyxiation e.g. montserrat 1997, mt. st helens

• tephra + ash flows - when volcanic rock + ash blasted into air = damages buildings, which can collapse under weight of this material e.g. iceland 2010, pinatubo 1991

• volcanic gases - such as sulphur dioxide + carbon monoxide, released into atmosphere - can travel long distances due to potency e.g. DRC, lake nygos (cameroon) - 1986

secondary hazards of volcanoes

• lahars - mix of rock, mud + water = travels quickly down the side of a volcano - occurs when heat of eruption causes snow/ice to melt OR when eruption occurs during heavy rainfall e.g. nevada del ruiz, mount pinatubo 1991, japan - mt. fuji, mt. st helens

• jokulhaups - snow/ice in glaciers melt after an eruption - causing sudden floods - can be dangerous e.g. iceland 2010

• acid rain - when gases (e.g. sulfur dioxide) are released into the atmosphere, harming plants + structures

tectonic classification theory

disaster = serious disruption of the community/society involving human, material, economic or environmental loss that exceeds the affected’s ability to cope with its own resources

disaster risk is calculated using this equation. a place is high risk if:

• capacity to cope is low

• vulnerable to hazards

• hazard - large/high intensity

degg’s model

hazard ≠ natural disaster - instead, disasters only occur when a vulnerable population (one that’ll be disrupted/damaged) is exposed to a hazard. therefore, if an invulnerable population experiences a hazard, it is not a disaster.

definition of hazards/disasters are not agreed upon

different organisation define hazards/disasters differently e.g.UN office for Disaster Risk Reduction (UNISDR) defines disasters as a serious disruption of a community involving widespread loss which exceeds their ability to cope alone. whereas, some classify hazards based on:

• volume of people affected (international disaster database- 100+ affected or 10+ dead)

• economic cost of the disaster - jobs lost, cost of repairs etc. UN sendai framework aims to reduce economic losses of disasters (established after huge economic losses in tohoku 2011)

• comparing tectonic disasters to previous events with predictions based on averages for the location - not reliable due to megadisasters

park model - depicts human responses to hazards

park model works as a control line to compare hazards, where:

• steepness of the curve - how quick an area recovers/deteriorates

• depth of the curve - shows the scale of the disaster

stage 1 - relief (hours-days): immediate local response - aid and search + rescue and immediate appeal for foreign aid

stage 2 - rehabilitation (days-weeks): services restored, temporary shelters open + hospitals, food + water distributed, coordinated foreign aid

stage 3 - reconstruction (weeks-years): restore area’s crops, ecosystem, infrastructure to the same quality or better + develop mitigation plans for future

pressure + release (PAR) model

PAR model is used to analyse factors which cause a population to be vulnerable to a hazard. PAR model is complex, as factors are interconnected + hard to measure. the idea is that if we can reduce the social factors, there is a reduction of pressure + vulnerability (whether physical, economic, social, environmental or knowledge-based)

1. root causes - often caused by economic, demographic or political processes - impacting populations. examples include weak governance, mismanagement by industry, NGOs/IGOs, high reliance on products impacted by hazards e.g. local agriculture or imports near volcanoes

2. dynamic pressures - local economic or political factors - affecting a community or organisation. examples include lack of training/knowledge within locals, rapid urbanisation, poor communication between government + locals, degradation of natural environment (mangroves), lack of basic services (health, education, police)

3. unsafe conditions - physical conditions that affect an individual. examples include lack of infrastructure, dangerous location of settlements, no warning system for locals, disease/fires - spreading through households

PAR model suggests that a series of these factors lead to a population’s vulnerability.

characteristics of a tectonic hazard profile - help decision-makers decide where to place human + financial resources

• frequency

• magnitude

• duration

• speed of onset (warning time)

• fatalities

• economic loss

• spatial predictability

hazards are very unpredictable, making models inaccurate in representing human responses to hazards.

questions to consider when evaluating these models:

• does this apply to every hazard?

• what is the timeframe?

• is it up-to-date?

• should models be more complex or more vague?

tectonic events can be measured by:

• volcanic explosivity index - measures the relative explosiveness of a volcano, based on height + duration, using a logarithmic scale of 1-8

• modified mercalli scale - measures the destructiveness of an earthquake, relative scale + subjective - based on movement felt (I-XII), does not consider social, economic or environmental impacts

• moment magnitude scale - measures energy released by an earthquake (0-9), simple system + social/economic/environmental impacts can be inferred

• richter scale - measures the amplitude of the waves, most used scale - ABSOLUTE. social/economic/environmental impacts can be inferred, logarithmic - but highest reading ≠ worst disaster

response to volcanic hazards

• prevention - tectonic hazards cannot directly be prevented, instead prevent the RISK e.g. stop building near volcanoes

• preparedness - monitoring, educating locals, evacuation plans, training response teams

• mitigation - direct intervention e.g. diverting lava, or strengthening at-risk buildings, evacuation zones, emergency aid + rescue

• adaptation - relocate, capitalise on opportunity e.g. tourism (eyjafjallajokull 2010), change profession

prediction of hazards

• earthquakes - cannot accurately predict, instead forecast the risk based on statistics - global seismic monitoring + historical records + feeling tremors

• volcanoes - somewhat predictable + accurate - monitor volcanoes by noticing changes to the tilt + top surface as this changes as magma builds

hazard management cycle - for all hazards

• preparedness - ready for an event to occur - public awareness, education, training, developing warning systems + preparation plans, stockpiling aid, food + water

• response - the immediate action after a hazards has taken place - evacuation, medical assistance, rescues, restoring water + electricity, restoring healthcare services

• recovery - long-term responses - restoring services, reconstruction of homes + infrastructure, reopening schools + businesses

• mitigation - strategies to lessen the impact of future hazards - barriers, warning signs, observatories, land use zoning, building codes + regulation, protective defenses (tsunami wall)

management approaches: modify the event

cannot control seismic activity, instead control buildings - e.g. aseismic infrastructure for earthquakes

micro: strengthening individual buildings

macro: large-scale + protective measure to protect communities

• land use zoning - preventing building in high-risk areas = low cost + reduces vulnerability BUT stops economic development on high value land + strict enforcement required

• resistant buildings - deep foundations, sloped roofs, springs help prevent collapsing - protecting people + property BUT high costs so low income citizens cannot afford

• tsunami wall - stops waves from travelling inland - reducing damage + provides security BUT very high costs, can be overtopped + deemed unattractive

• lava diversion - barriers + water cooling to divert and slow down lava, low cost BUT only works for low VEI lava

management approaches: modify the vulnerability

• high-tech scientific monitoring - monitors volcanic behaviour + can predict eruptions sometimes = warning + education saves lives BUT costly so LICs don’t monitor + this method does not prevent property damage

• community education - low cost +implemented by NGOs + saves lives BUT doesn’t prevent property damage + hard to implement in isolated/rural areas

• adaptation - relocating - saves lives + property BUT cannot be done with high population densities + disrupts lives

management approaches: modify the loss

• short term aid - reduces death toll + keeps people alive until long-term aid arrives BUT high costs + difficult in rural areas, emergency services are limited + poorly equipped in LICs

• long term aid - reconstruction improves resilience through future land use planning BUT high costs + forgotten by media quickly

• insurance - compensation for loss - allowing people to recover economically BUT does'n’t save lives + many don’t have insurance

importance of stakeholders

• the role of communities - local recovery operations, clear debris, set up temporary shelters = importance

• the role of NGOs - provide funds, coordinating rescue efforts, develop reconstruction plans. TNCs may work with NGOs for charity events

development + governance

some government may choose to invest in development + economic growth instead of hazard mitigation - making population more vulnerable to hazards

risk poverty nexus

poverty is a factor + consequence of natural hazards as low income populations are more affected by natural hazards.

communities can face inequalities such as:

• asset inequality - housing, security of tenure + agricultural productivity

• political inequality - certain people hold more influence + power - usually the wealthy + elite

• social status inequality - linked to space but links to regular income + access to services

• entitlement inequality - unequal access of public services, welfare + rule of law

factors that can contribute to an area’s vulnerability

• unstable political governance - impacts preparedness + recovery efforts

• population density - harder to control as it increases

• isolation/accessibility - poor transport links which impacts rescue efforts

• level of urbanisation - higher population density + infrastructure so impacted more

governance

• meeting basic needs - when met, population is less vulnerable to secondary hazards e.g. disease

• planning - reduces risk

• education - raising awareness = prepared population

• corruption - vulnerability increases with a corrupted government as important investment in services/hazard mitigation is being used elsewhere

mega-disasters

• affects a large population or large area

• hazard management is made less effective

• scale of the impact - requires international support + aid

• low in probability

• often interrupts international business e.g. tohoku 2011 - TNCs e.g. Toyota + BMW operate/source products in japan - lost potential revenue OR 2011 eyjafjalljokull - ash clouds cause significant disruption of air travel - halt of goods + trade into the EU e.g. flowers from kenya could not be transported

case study: haiti 2010 earthquake - “one of the worst disasters of our time”

context: haiti is an LIC, with a history of national debt, prejudicial trade policies, corrupt governance + foreign intervention into national affairs = pre-existing poverty (77% live on less than $2/day) + poor housing conditions, healthcare + sanitation = increased the death toll. haiti is also located on a plate margin, with limited accessibility (hilly topography), = experiences extreme weather conditions often = multi-hazard zone

primary impacts:

• deaths toll between 100,000-160,000, yet government claims 220,000-316,000 - corruption/deceit

• 250,000 residencies destroyed essential services + communication cut out

• $8.5 billion in damages - 90% of gdp

• 2 million displaced

secondary impacts:

• rivers became polluted + toxic

• cholera outbreak in 2010 - due to unsanitary conditions

• prison was damaged - outbreak of >4000 criminals = widespread violence + crime

immediate responses:

• many responded to aid appeals - 4 million received food, 1.5 million received emergency shelter materials + most-watched telethon “hope for haiti now” - received $58 million

• search + rescue teams, medical aid + engineers

long-term responses:

• environmental clear up + regeneration of ecosystem

• $13.5 billion pledged - yet some went missing (corrupt)

• 2020 - new strategic framework for disaster management - supported by UN

haiti is the poorest country in the western hemisphere - so it relied on this aid for years to come - still not fully recovered

case study: christchurch earthquake 2011 (6.3)

the earthquake was caused by a 15km long fault rupture along the southern edge of the city + fault slopes southward beneath the port hills + new zealand lies along a convergent plate boundary (australian + pacific) + was 10km from CBD

short term impacts: 185 killed, 6654 with major injuries, heritage sites damaged, soil liquefaction on eastern part of the city (built on a swamp) → buried property + sewage floods

long term impacts: power outages, port + roads damaged so vehicles stranded, schools closed, the city centre was rubble

prior to the earthquake, the canterbury plates hadn’t experienced a major earthquake in thousands of years → unprepared as a previously unknown fault ruptured = no prior management

response: government activated national crisis management immediately + declared a national state of emergency. 75% of the electricity was restored within 3 days. the CBD remained closed for 2 years. water + sewage took years to restore in liquefied areas. support subsidies helped companies to operate + paid for staff’s wages.

governance: declared a national state of emergency + the first time since the civil defence emergency management act 2002. local, national + regional government came together to provide a single unified response.

other factors that influenced vulnerability: prior earthquake in 2010 weakened buildings + many central buildings are old, earthquake happened at lunchtime in a densely populated area → increases impact. however, nz is a developed country, so they could afford to rebuild

case study: mount merapi, indonesia 2010

• located on a destructive plate boundary → subduction occurred

• composite volcano with VEI 4

• impac