tectonics alevel edexcel

Define natural hazard

A naturally occurring process or event that has the potential to affect people

Define natural disaster

A major natural hazard that causes significant social, environmental and economic damage

California as a multiple hazard zone

Droughts - high pressure area (anticyclones) la Nina cycles ( no evaporation from eastern pacific so no precipitation)
Earthquake Sam Andreas fault 2 or 3 each year with mag over 5.5 (potential to damage structures) San Francisco 1906 7.8 Richter scale along with subsequent fires destroyed most of the city
Earthquakes under Pacific Ocean cause tsunamis on California coastline - Alaska earthquake in 1964 triggered a tsunami killing 22 and destroying 1300 homes
-landslides, steep slopes of the rockies, also coastal land (la conchita)
-more than 70% live within 50km of fault line

• building on unstable land (marina district)
  Large economy means great losses
  20% in LA live below poverty line

Vulnerability

The ability to anticipate, cope with,resist and recover from a natural hazard

Nepal case study

7.8 mangnitude (Indian + Eurasian plate)
Killed nearly 9000
3mill homeless
Vulnerable -
One of the worlds poorest (2016 ranked 197th)
Weak infrastructure
Around 100 aftershocks
In himalayas (landslides
Lost 25% of GDP
Tourism reduced.

What are the four driving forces for plate movement?

Mantle convection
Slab pull
Ridge push (sea floor spreading)
Subduction

Which is on top? Lithosphere or asthenosphere

lithosphere

Inner core

6000 degrees
Solid iron

Outer core

4500-6000
Semi molten
Nickel and iron

Mantle

Upper part solid
Lower part semi-molten forming the asthenosphere

Oceanic crust

Thin
Dense
6-10km

Continental

Older
Thicker
Less dense
45-50km thick

Lithosphere

Crust and upper mantle, the solid layer in which tectonic plates are formed

Paleomagnetism

The study of the earths past changes in magnetic feild( determined from rocks, sediment or archeological records)

Destructive ocean+ continental formations

Deep ocean trenches
Fold mountains
Earthquakes (benioff zone)
Volcanoes (explosive)
Among the most seismically active areas of hazard

Ocean/ocean destructive

Denser or faster subducted first
Ocean trenches
Magma rises up from Benioff zone to form underwater volcanoes
Island volcanoes (island arcs)
Shallow earthquakes or deep
Marianas trench (pacific faster moving subducted under Philippines plate)

Continental/continental convergent

Collision margin occurs
Fold mountains (Himalayan's)
Shallow earthquakes

Ocean divergent boundary

Mid ocean ridges with transform faults due to spreading at different rates
Submarine volcanoes, can create island ie Iceland on the mid Atlantic ridge
Shallow focus earthquakes (low risk no humans)

Divergent continental

Rift valleys
Crust stretches and breaks into sets of parallel faults, the land between these faults then collapses, forming steep sided valleys.
The East African Rift

Conservative

Major break in crust (fault)
Large scale = transform fault
Powerful earthquakes

On average how many yearly deaths by earthquake

10,000

What's the difference between the focus and the epicentre, and what can a focus also be called?

A focus is where the point inside the crust where pressure is released (also called the hypocentre) and the epicentre is the point on the surface directly above the epicentre

What type of waves are primary and secondary and why?

Body waves - because They travel through the earths body

What type of waves are love waves

Surface waves because they travel along the earths surface

P waves

Push through crust mantle and core Fastest
Travel Through solids and liquids
Travel via compressions
Only damaging in the most powerful earthquakes

Secondary waves

Shake through crust and mantle Slower
Only through solids
Move in a sideways motion at right angles to the direction of travel
More damaging

L waves

Slowest
Last to arrive
Most damaging (shake the earth side to side)
Focus all their energy on earths surface
Larger

What measures an earthquake

Seismometer

Moment magnitude scale

Measures magnitude
Measures total energy released by earthquake at the moment it occurs (seismic moment)
Measures : size of seismic waves
Amount of slippage
Area of fault broken
Resistance of affected rocks
Generally goes up to 10
Logarithmic

Modified mercalli intensity scale

Measures intensity
Observations of the effect on people structures and the environment
I to XII

Primary effects and examples of earthquakes

Ground shaking - ie Turkey 2023 feb diyarbakir 3000 building fell
Crustal fracturing - myanmar in a road

secondary effects of earthquakes

Liquefaction - Christchurch New Zealand
Landslides and avalanches - Nepal
Tsunami - 2004 Thailand tsunami

1989 Loma prieta earthquake

6.9 near San Francisco
Marina district build on man made landfill that was soft and Sandy and amplified the love waves increasing shaking increasing damage on infrastructure - liquefaction also happened
Two level cyprus freeway collapsed (causing 42 of 67 deaths)
The part of the freeway that collapsed was on soft mud, whereas parts built on the firmer ground remained standing.

An example where aftershocks caused more damage than the initial earthquake

Christchurch New Zealand 2011 6.3 aftershock caused more deaths (185) and damage than the initial 2010 earthquake mms 7.1 no deaths
(This was because the focus was more shallow and the aftershock was centred closer to the city)

Predicting earthquakes

US geological survey forecast a 67% chance of San Francisco experiencing a sever earthquake in the next 30 years

What does research focus on about predicting earthquakes

Finding precursors to earthquakes
None are proving reliable

Example of intraplate earthquakes and why scientists think they occur

Three earthquakes of around 7.5 magnitude in central USA between 1811 And 1812

They may occur due to old faults build up stresses causing them to become active again

Eyjafjallajokul

2010
Flights across Europe cancelled for a week (ash clouds could stop plane engines working)
100,000 flights cancelled worldwide
10 million passengers unable to board to or from Europe
Worldwide airlines lost 1.7 bill revenue
European economy lost 5 bill
Kenyan exports of flowers and vegetables had to be dumped (loss of 1.3 mill per day revenue) 20% of their economy is based on this

How many people worldwide are at risk from volcanoes

500,000,000 people

Pyroclastic flow example and what it is

Mount St Helens
Hot broken fragments of rock ejected with great velocity
1980 eruption hundreds of square miles were reduced to wasteland 1bill damage

Tephra example and what it is

Monserrat
Collective term for all airborne or ground flowing pyroclasts including solidified magma
May spread over vast distances
The ghost town of Plymouth became isolated when the 1997 eruptions Coated everything in ash
4000 people left

Lava flows example and what it is

Mt nyiragongo
Forms solidified surface
May cause fires and burial of land objects
Low risk to life
Contained the worlds largest continually active lava lake - in 2021 lava leaked 400,000 forced to flee their homes 32 died

Volcanic gases

Ash laden gases HCl
Co2 SO2
Toxic and contribute to acid rain which can ruin crop yield and ruin ecosystems
Lake nyos (1700 deaths due to carbon dioxide)
1986

Lahars

Volcanic mudflows when rainwater loosens tephra ie mount pinatubo 1991
Lahars washed through air base 840 deaths
Every bridge within 30 km destroyed
Several lowland towns flooded
1991

How important is ridge push compared to slab pull?

Ridge push contributes to 1/10th the force of slab pull

What percent of earthquakes happen in the ring of fire

70%

What is the violence of a volcanic eruption determined by?

Amount of dissolved gases in the magma
How easy is can escape

Explain a volcanic hotspot

An area in the mantle where heat rises as a thermal plume - high heat and low pressure causes the lithosphere to melt, magma rises up through cracks to the surface and erupts to form an active volcano.

Alfred Wegener

17th century people thought Africa and South America fit together
1912 - he proposed continental drift
Fossil evidence - the same reptile fossils (mesosaurus) found in South America and Africa (suggests they were once joined)
Fossils of the same green plants found all over the world (could have been transported by sea or air however)

Glacial evidence
300mil years ago glaciers covered Southern Hemisphere
The pattern they made as they moves across earths surface doesn't make sense unless continents were arranged as he proposed

Mountains formed together

What was harry Hess theory

1962 sea floor spreading
Age of rock proves this
Proved by paleomagnetism

Monserrat

1995 soufriere hills volcano for 5 years
7000 moved
Plymouth the capital containing all main services destroyed
Tourist industry collapsed
Agriculture affected
Aging population - young people moved out

Volcanic Explosivity Index

Logarithmic
Amount and height of volcanic material ejected
How long eruption lasts
Qualitative descriptive terms ie gentle
0-8

8 on VEI

Yellowstone caldera 600,000 years ago

What was the VEI of pinatubo

6

What was the VEI of Mt St Helens?

4.5

How to predict volcanoes

Tiltmeters
Seisometer to measure small earthquakes from magma rising that breaks small rocks
Bulging of volcano via radar

How does a tsunami form

Large underwater earthquakes
Crust thrust upwards displacing a water column creating a wave with a small waveheight and a long wavelength that moves outwards in all directions when water shallows, friction is created on the bottom of the wave so the energy is concentrated into a smaller amount of water and wave height increases while wave length decreases.
Tsunamis are a series of waves

Predicting tsunamis

The DART system
Seismic sensors
Seabed sensors
Surface bouys to monitor changes in sea level and pressure
When tsunamis are detected satellite information sent to warning stations

Affect of Indian Ocean 2004 tsunami on Sri lanka

31000 deaths

Why and when was the Indian Ocean early warning system developed

2006 - after devastating impacts of Boxing Day tsunami

What issue in warning occurred in 2011 Japan earthquake

Japans extensive tsunami and earthquake wanrning systems one of the biggest in the world
Following the 9.0 earthquake the Japan meteorological agency issued a tsunami warning within 3 mins
However size of the earthquake + tsunami underestimated, so lack of sufficient preparation or evacuation

2004 Indian Ocean tsunami

One of the worlds worst human disasters
9.0/9.3 earthquake
Indian Ocean floor displaced by 15 m
Countries around the entire span of Indian Ocean - closest Banda ache Sumatra 17 metres high (15 mins away)
Maldives 4 metre high
Even South Africa affected
Nearly 300,000 dead
1.7 homeless

Why was 2004 tsunami so destructive

Number of countries affected were low income so no money for defenses
No warning system in place
In some areas ie Sri Lanka mangrove forests cut down for tourism reducing the natural protection
Low lying coastilines of many countries
Epucentre close to densely populated communities

Impacts of 2004 tsunami

Sumatra 1500 villages destroyed
Andaman and Nicobar islands cut off as all jetties washed away
Sri Lanka -60% of fishing fleet destroyed
Thailand - 120000 lost tourism jobs 25$ mill loss a month
Freshwater and agricultural soil contaminated by salt water
Most vegetation and topsoil removed up to 800m inland
Over $10 bill loss

Hazard risk formula

Risk = hazard x vulnerability / capacity to cope

Resilience

The ability to protect lives, livelihoods and infrastructure from destruction and to restore areas after a natural has occurred

Hazard event

A natural hazard (such as an earthquake, volcanic eruption or tsunami)

Mount sinabug Indonesia

Farmers work in tanah Karl North Sumatra as mount sinabug erupted in August 2010
30,000 people evacuated

Comparing Haiti 2010 and Japan 2011

mag 7.0 in Haiti, mag 9.0 and tsunami
Dead + missing, Haiti 250,000, Japan 20,000
Made homeless haiti 1.3 mill, Japan 130,000
Economic cost haiti 14bill, Japan 240 bill
GDP per capita haiti, 1300$ Japan 40,000

Haiti 2010 earthquake details

North American and Carribean plate
Conservative
Liquefaction
Epicentre 24km from Port au Prince (home to 2 million)
Shallow focus 13km

Issues with Haiti vulnerability

Developing - money spent on immediate problems
Corruption on local and national level- no commitment to improve infrastructure and living standards, corrupt officials ignoring business codes (bribes)
Poorly built slum housing Port au Prince
No planning
Haitians still live in poverty

Impacts on Haiti

One airport, several ports and a few main roads - damaged, aid supplies not distributed effectively, slowing rescue efforts leading to more deaths
-1/4 government officials killed, key buildings destroyed, government less able to organise recovery and relief
-2010 outbreak of cholera, lack of medical supplies and trained healthcare professions, by 2015 9000 dead from cholera and around 700,000 affected

Haiti's recovery

2015 still recovering
13 bill aid (only 10 percent remained in the hands of Haitian government and organisation because of corruption fears)
International organisations provided emergency services - managing projects by bringing in their own staff (reduces self sufficiency and doesn't give needed money to local industries)
2015 - 80,000 Haitians lived in temp camps
New infrastructure built
More resilient - following event hurricane Sandy included a response of warning to go to higher ground

China earthquake

2008
7.9 Sichuan SW China
Mountainous - landslides 1/4 of deaths
50 mill people affected
5 mil homeless
Corrupt building codes - Sichuan thousands schools fell 5335 children dead (government buildings remained stood)

Why is death toll different for Haiti + japan

Epicentre near rural areas and small towns (Haiti near Port au Prince)
Wealthier economy, able to pay for rescue and aid
China's strong central government able to respond as they weren't destroyed

China's response

130,000 soldiers and relief workers
Medical services quickly restored
People in danger of landslides relocated
Government gave 10 bill for rebuilding
Chinese banks wrote off debts of people without insurance
Within 2 weeks rebuilding

Long term China responses

2 years after
97% of 29704 reconstruction projects started (earthquake proof)
99% of farmhouses 196000 rebuilt
-yongchang, after 2008 40,000 moved here, immediately cracks appeared in brand new homes - a local official arrested for taking bribes
216 transport projects under construction or completed

Japans preparation

Building regulations strict -75% built earthquake proof, low level of corruption strictly enforced

• well developed plan (ten m high tsunami walls, evacuation shelters,evacuation routes) residences wquipped with emergency kits, early warning system
• education + preparedness, regular drills in schools
  -however power plants not built to withstand huge tsunami, lack of planning prep and oversight at Fukushima led to the meltdown

Response of Japan

110,000 troops mobilised
Tv and radio coverage of info
Bank of Japan gave 183 bill to banks to protect economy
Accepted rescue and recovery team from other countries (in Haiti this was slowed by poor damages infastructurr and damaged government coordination, China didn't like help from other countries so no procedures for international aid in place - it was slow)

Why are the number of disasters increasing

Improvements in recording and monitoring = more reporting
Improvements in communication
Greater population
More impermeable building materials greater flooding risk

What is happening to the financial cost of disasters

In 1990s averages 20 billion per year in damage
Between 2000 and 2010 about 100 bill

What's happening to deaths globally due to natural disasters

Decreasing due to better warning systems building codes and preparedness

Hydrometeorological Hazards

Natural hazards caused by climate processes (including droughts, floods, hurricanes and storms)

Philippines MHZ

Convergent plate boundary - Philippine plate and sunda plate earthquakes And volcanoes
North and east costs face Pacific Ocean tsunami prone
Lies in SEA typhoon belt 15 per year average (flooding and landslides)
22 active volcanoes 30% of pop within 30 km of volcano
Landslides - steep topography, high deforestation, high rainfall

Why is Philippines vulnerable

rapidly developing lower middle income Rapid urbanisation and high pop density
Poor live in coastal poorly constructed coastal areas prone to flooding and tsunamis
25% pop live in poverty

Difference between average deaths of disasters in low income countries and high income countries

Between 1994 and 2013
322 deaths, 105 deaths

2006 Philippines earthquake

Killed 15, injured 100, damaged and destroyed 800 buildings
Generated local 3m tsunami
Triggered landslide, breaching crater wall and fell into lake causing a flood that washed away houses

Why is the ability of response in Philippines so hard

Strings of disasters ie
3 disasters in 3 months in 2013
Earthquake killed 223
Then typhoon Haiyan killing 6200
Then floods in January killing 64
Government and aid agencies in a constant state of emergency

4 stages in hazard management cycle

Mitigation
Preparation
Response
Recovery

What's included in the park model

Hazard response curve
Pre disaster, relief, rehabilitation, reconstruction

Mitigation strategies

Land use zoning
Diverting lava flows (usually unsuccessful lava flows unpredictable ) - 1983 mount etna successful
GIS mapping - used in all stages of management cycle, identifying where evacuation routes should be before, rescue and recovery, shows locations of airstrips, locations of towns
Hazard resistant engineering - sloped roofs so ash doesn't collapse, rubber shock absorber foundations, structural retrofitting, can also be done cheaply ie in Pakistan , bales of straw with strong plastic netting effective

What are hazard adaptation strategies?

Reducing vulnerability to impacts
High tech monitoring - GIS maps, early warning systems, atelier communication, mobile phone technology
Public education - Japan 4 times drill per year, annual disaster prevention day

Crisis mapping

Crowd sourced information
Ie Haiti Ushahidi set up a map that helped with aid and rescue workers , people gave info about where people were trapped
Can be used for disaster adaptation ie in Nepal after 2015 volunteers mapped data about quality of infrastructure to provide a picture about vulnerability and how to improve preparedness

Hazard adaptation: modelling hazards

Computer systems used by decision makers to develop plans and strategies to reduce impacts

Community preparedness in hazard adaptation

2004 tsunami elders of Thailand's mike. Tribe noticed unusual movements in a bay, then ordered villagers to run to the hilltop , so only 1 of 200 villagers died. Community preparedness best when formalised ie committees that liaise with government abs school and planners , they may create a list of the vulnerable, organise drills, provide first aid cousses

Response aid

Emergency aid - food water shelter
Short term - restoring water supplies, temp shelter
Long term - reconstructing infrastructure, repairing the economy, managing adaptations for the next disaster

NGOs and Pakistan 2005

7.6 mag
73000 deaths
3.5 mill homeless
Mountainous
Emergency aid :Water sanitation facilities destroyed
NGOs provided 500,000 tents 6 mill bankers
Short term aid; water supplies re established
Long term: farmers given seeds and tools, new schools and medical centres, community based risk reduction programmes developed

Insurance in hazard management

Poorer countries can't afford
Japan could

Role of communities in managing loss

They help in instant search and rescue
Create temporary shelters and clean debris from access roads (Afghanistan in 2015, villagers in mountain communities traveled to more remote areas to help)
Community groups vital in long term rebuilding and resilience improvement