geography - natural hazards

Extended as of 9/3/26 to include the last few lessons of the topic.

types of hazards

tectonic: earthquakes, volcanic eruptions (and associated ash fall), tsunamis

atmospheric: tropical storms, droughts, tornadoes

geomorphological - landslides, flooding, mudflows

biological: forest fires

factors affecting hazard risk

population density, development, land use, climate change, geographical location, education etc

earth structure

crust → asthenosphere (part of the mantle) → mantle → outer core → inner core.

crust: 0-70km, broken into plates (continental and oceanic), solid. forms the lithosphere with the uppermost mantle layer - solid and brittle, about 100km thick

asthenosphere and mantle - able to flow, but not melted due to pressure. heat increases the deeper you get

outer core - liquid iron and nickel, incredibly hot

inner core - solid iron and nickel. about 5500^oC.

tectonic plate movement

convection currents: convection currents in the mantle (material heated by the core rises, travels along and drags the plate above it, sinks and creates a convection cell). generally discredited now however

ridge push / slab pull: newly formed oceanic plates push away due to gravity, causing ridge push to move plates. additionally, at destructive plate margins, subducted plates pull the rest of the plate with them, causing motion.

volcanoes and earthquakes - location

mostly occur on plate boundaries, though volcanoes do not form on conservative boundaries.

plate boundaries - conservative

conservative - two plates moving side by side, either in the same or opposite directions. can cause strong earthquakes as friction builds and is released suddenly (up to mag. 8). likely to cause aftershocks. example: San Andreas fault line.

plate boundaries - destructive (general)

destructive: plates moving towards each other and colliding. multiple subtypes (oceanic-continental, continental-continental, oceanic-oceanic). some can cause volcanoes, all can cause earthquakes.

plate boundaries - destructive - oceanic-continental

oceanic-continental destructive boundaries cause the denser oceanic plate to be subducted, forming an oceanic trench. can cause earthquakes from friction release. can cause volcanic eruptions as ocean water enters the mantle, reducing its melting point and forming magma, which rises, collects in magma chambers and can cause eruptions. the continental plate is crumpled by the pressure and forms fold mountains.

plate boundaries - destructive - continental-continental

plates collide, and are unable to submerge into the mantle due to composition. they crumple upward, forming fold mountains, and can cause shallow-focus earthquakes. cannot cause volcanoes

plate boundaries - destructive - oceanic-oceanic

older plate subducts the younger plate, as plates become colder and denser as they age. ocean water enters the mantle, causing magma formation, which cools on connection with ocean water, forming volcanic island arcs. can cause both volcanoes and earthquakes.

plate boundaries - constructive

oceanic-oceanic exclusive, where plates move apart. mantle wells up in the lithosphere, forming new crust. can cause volcanic eruptions (shield volcanoes specifically) and earthquakes.

effects of tectonic hazards - earthquakes - primary

things directly caused by the earthquake. includes deaths and injuries from collapsing buildings or falling debris and buildings, transport and pipework being destroyed, cutting off shelter, access and essential services (eg water, heating)

effects of tectonic hazards - earthquakes - secondary

things caused by the disruption of the earthquake. includes delays of emergency services from damaged infrastructure and roads, fires from ruptured gas pipes or power cables, burst water pipes causing shortages of clean water and economic activity being disrupted, putting strain on the government and families

effects of volcanic eruptions - primary

lava flows, ash, and pyroclastic flows destroy infrastructure and injure or kill people, travel is disrupted due to ash clouds, and ash and gases contaminate water supplies

effects of volcanic eruptions - secondary

losing access to remote areas, slowing rescue efforts, floods from glaciers and snow melting, heavy rain combining with ash creating lahars/volcanic mudflows. however can cause more tourism and enriches soil.

immediate responses to tectonic hazards

issuing warnings (ex. after an eruption/quake if activity is likely to continue)

rescue teams searching for survivors (often HIC-lead, even in LICs, due to funding issues)

treating the injured (ex giving painkillers or antibiotics, or full surgery for the most heavily affected. field hospitals are often set up to lessen pressure on hospitals)

providing food, drink and shelter

recovering bodies - after the injured are out, recovering bodies is prioritised

extinguishing fires

long-term responses to tectonic hazards

rebuilding and repairing properties and infrastructure

improving building regulations

resettling locals

developing economic recovery opportunities

installing monitoring equipment

HIC earthquake case study - L’Aquila

mag 6.3 quake in 2009, L’Aquila, central Italy.

killed 309 people, including 20 children, injured a further ~1 500 damaged between 3 000-11 000 buildings, made around 40 000 homeless. caused an estimated $1.1 billion in damages.

aftershocks caused further damages including landslides and rockfalls, damages caused housing prices to increase and tourism to decrease

hotels provided shelter for 10 000 people, and 40 000 tents were distributed. Italian Red Cross searched for survivors with 7 dog units, 36 ambulances and a temporary hospital within an hour. many bills were suspended, and free mobile calls etc. were offered. it was granted $552.9 mil for rebuilding

residents did not have to pay taxes during 2010, homes were rebuilt and students were given free public transport discounts and exempt from university fees

LIC earthquake case study - Nepal

mag 7.9 quake in 2015, Nepal, 60km northwest of the capital.

killed 8 632 and injured 19 009, made 3 million homeless, affected over 8 million. 1.4 million needed support with access to food, water, and shelter access, 7 000 schools and 50% of shops were destroyed. estimated costs: $5 billion

triggered avalanches and landslides, blocked roads. at least 19 deaths on Mt. Everest from avalanches, and 250 missing in the Langtang region due to an avalanche. tourism declined, and rice seeds were destroyed, causing food shortages and income loss

over $1 billion in aid from India and China, as well as 100 search and rescue responders, medics and disaster and rescue experts, and 3 Chinook helicopters provided by the UK. 0.5 mil tents were provided, and field hospitals were set up, and Facebook launched a safety feature

asian development bank provided $3 mil in immediate relief and $200 million for first rehabilitation. repair work fixed roads and buildings (inc, 7 000 schools), stricter building codes were introduced etc

reasons people live close to volcanoes

• mining - magma + volcanic gases bring precious metals, giving economic opportunities

• geothermal energy - steam from underground can be harnessed to produce electricity, or as a tourist attraction (ex. the blue lagoon)

• tourism - volcanoes alone are appealing, and come with hot springs and geysers which are further attractions for tourists.

• agriculture - mineral- and nutrient-rich soils are ideal for farming

reducing earthquake risk - monitoring and prediction.

approximate earthquake time, date, magnitude and location predictions are attempted through monitoring radon gas release from cracks in the earth’s surface, foreshock measurements, and pattern mapping

reducing earthquake risk - protection

buildings are designed to standards to protect from earthquakes, including using seismic isolators (able to move with the earthquake - shock absorbers), cross bracing (crisscrossed steel bars bracing walls), using shear walls (concrete with steel bars), counterweights (weights on the roof which counteract the waves)

reducing earthquake risk - planning

educating people on how to respond to earthquakes - eg fastening furniture, preparing emergency supplies in advance, knowing how to turn off gas, electricity and water supplies and running drills (eg Japan’s, yearly on the 1st Sept)

reducing volcanic eruption risk - monitoring and prediction

detecting changes in the shape of the volcano as magma rises, levels of gas around the volcano, thermal heat sensors on the surface, measuring for small earthquakes. this allows evacuation plans to be put into place

reducing volcanic eruption risk - protection

mostly just evacuation as you can’t do much about a volcano. however, a few cases of protection exist: emergency crews pumped seawater onto the lava flow for over 4 months to divert it from the vital harbour in Iceland (successful, though around 1/5 of the town was still destroyed), and building walls to divert the flow. buildings are created with reinforced roofs and air filtration system.

reducing volcanic eruption risk - planning

still education - creating exclusion zones and educating people on what to do if evacuation is impossible

global atmospheric circulation

circulation is represented by 12 cells, mirrored across the equator and north-south divide - hadley cells directly above and below the equator, ferrel cells above these, and polar cells at the poles. each one is a convection current. displayed best in a diagram as shown

Hadley/Hadley/ split is at 0^o/the equator, Hadley/ferrel cell at 30^o, and ferrel/polar is 60^o

the equator is an area of low pressure, high heat and high rainfall. 30^o gives high pressure/high heat/low rainfall. 60^o reflects the equator, and the poles / 90^o reflect 30^o

surface winds blowing toward the equator are called trade winds, and toward the poles are called westerlies.

tropical storms

areas of extremely low pressure with high winds and rainfall.

split into 5 categories dependant on wind speed and damages (74-95, 96-110, 111-130, 131-155, 155+). categories are numbers with 1 being weakest

made up of bands of cloud - outermost bands being weakest, and the central band or eye wall is the most violent. strength is caused by pressure difference. these can be over 13km tall.

the eye in the centre is free of cloud and has no wind or rain, due to flow of dry air from the atmosphere. 16-48km large.

tropical storms - formation

formed over warm waters at a minimum of 27^oC, and between 5-30^o lat.

air is heated, and rises rapidly, drawing up more air and large volumes of moisture, causing strong winds.

the air is spun by the Coriolis effect, creating the eye of the storm.

air that has risen forms cumulonimbus clouds, causing the rain and giving off heat.

cool air sinks into the eye. it travels with the prevailing wind, and loses power as it travels over land.

climate change’s effect on tropical storms

increases distribution, as more oceans hit 27^oC for longer periods, frequency, as storm season lengthens, and intensity, as higher temperatures supply storms with more energy, warmer air holds more moisture (4% rise in water vapour), and rising sea levels cause higher storm surges.

effects of tropical storms

people killed/injured by debris, building collapse, flash flooding and storm surges, destruction of buildings + infrastructure, loss and contamination of supplies (eg from sewers flooding)

people left homeless, waterborne disease outbreak, transport being blocked, businesses being forced to close, crops and livestock killed

responses to tropical storms

evacuating people from at-risk areas, rescue operations, providing emergency supplies and temporary shelters, recovering bodies, aid from governments and charities

repair and rebuilding work, rehousing, improving forecasting, warning systems and building codes, providing grant, business loans and tax breaks

typhoon Haiyan case study

cat 5 typhoon in the Philippines, near Tacloban, with wind speeds of up ton 195mph

buildings damaged and destroyed (90% of tacloban itself, 1.1 million houses and tonnes of crops), services lost (eg. electricity), flooding extending to 1km inland, killed 6190, injured 29 000, made 4 100 000 homeless and 14 100 000 were affected, costs of around $12 billion.

infection and disease spread due to contamination, fighting over supplies killed a further 8, power supplies were cut for months, education was disrupted, 800 000 litres of oil contaminated fishing water and 10 hectares of mangrove, looting was rife, rice prices increased by 12%, flooding caused landslides, airport was badly damaged

govt. issued televised warning to people to prepare and evacuate - 800 000 people evacuated, many of whom sought refuge in a stadium in Tacloban and were killed when it was flooded. govt. provided essentials and medical supplies, and a curfew was introduced to reduce looting. 1 200+ evacuation centres set up, airport reopened after 3 days allowing aid in, and over $1.5 billion aid pledged

cash for work programme paid for debris clearance and rebuilding efforts, and rebuilt buildings aim to provide better protection. mangroves have been replanted and a no-build zone has been set up.

planning for tropical storms - monitoring and prediction

tropical storms can be picked up on during formation, and pathing can be predicted. hurricane watches are issued if anything is picked up on. this is more of a HIC thing due to costs

planning for tropical storms - protection

building storm shelters - specialised buildings with windows covered with metal shutters, built off the ground on deep-pile concrete pillars to dissipate energy and are made from reinforced concrete.

sea walls on coasts reduce storm surges

planning for tropical storms - planning

stocking up on essentials, knowing where storm shelters are, evacuating i/a

weather hazards in the UK

the UK is prone to storms, which have been increasing in regularity and severity in recent years. periods of drought and heavy rain are both increasing in regularity. likewise, wind strength has been increasing, causing property damage etc

mean temperatures are increasing, especially in summers. all temperature records have been broken in the last 5 years, and are often rebroken year on year. this worsens aforementioned droughts

the 2022 heatwave caused UK temperatures to exceed 40^oC for the first time in the century. this was worsened severely by climate change, and caused closures across the country as well as problems regarding heatstroke or water-related deaths trying to cool down (5 counts) etc. national warnings were issued, and gritters were deployed to prevent roads from melting.

evidence that UK weather is increasing in extremity

• 2022 was a record-warm year for the UK (exceeding 40^oC from a past high below 39)

• 2022 received 6% below avg. rainfall, most of which occurred in February

• sea level around the UK has risen by 11.4cm over the last 30 years

• projections show this will continue to worsen unless drastic change is made

evidence of climate change

• sea level rise of 1.9cm over the last century

• ocean temperatures are the warmest recorded since 1850, glaciers are retreating

data gathered from ice and sediment cores support this. by analysing gases trapped in the ice, temperature estimates can be gathered, giving data up to 400 000 years into the past. similarly, tree rings and pollen analysis can give readings for slightly more recent and other more distant changes respectively.

temperature records provide reliable data for the short term.

causes of climate change

greenhouse gases in the atmosphere absorb and emit more of the infrared waves emitted by the earth from the sun. this keeps more of the heat in the atmosphere, increasing global temperatures.

as more greenhouse gases are released, this effect is magnified. this happens from burning fossil fuels, deforestation, agriculture, landfill waste decaying (releases methane) etc.

orbital changes (milankovitch cycles - earth’s tilt + orbit around the sun) magnify the effect, as do eruptions releasing more CO₂ independent of human activity and solar output increasing the amount of heat released in the first place

management of climate change

mitigation involves reducing causes, and includes using green energy sources (expensive, can have other ecological impacts), carbon capture (also expensive), afforestation (takes land, expensive, if poorly managed the forests will still die) and international agreements (rarely followed).

adaptation includes changing agricultural practices (eg what crops are grown where), managing water supplies (increasing transport schemes), and coastal defences to reduce consequence of rising sea levels.