P1 - Tectonics Flashcards
What is the inner core?
- the hotest part of the earth
- it’s temp ranges from 4500-6000 degrees celcius
- it is solid and mostly consists of iron
What is the outer core?
- semi-molten and mostly consists of liquid iron and nickle
- it surrounds the inner core
What is the mantle?
- it includes the asthenosphere- semi-molten on which tectonic float
- it surrounds the core and is the widest layer
What is the crust?
- forms the outer shell of the earth
- two types: oceanic and continental
What are the four processes that make plates move?
- Convection
- Slab pull & ridge push
- Subduction
- Sea floor spreading
What are convection currents?
Magma rises as it has been heated by the core, it is then blocked by the crust so then begins to fall back down to the core as it cools
Because the magma hits the crust it will overtime cause the plates to pull apart
NEED TO DO SLAB PULL & RIDGE PUSH, SUBDUCTION AND SEA FLOOR SPREADING
Destructive plate boundary:
1. What happens at this boundary?
2. What hazards can be found?
3. Example
- Oceanic plate subducts underneath the less dense continental plate. The oceanic plate melts as it reaches the subduction zone and can force its way to the surface as magma
- Highly destructive earthquakes, volcanoes, tsunamis
- Nazca Plate, South America
Constructive plate boundary:
1. What happens at this boundary?
2. What hazards can be found?
3. Example
- Two plates move apart from each other. Magma wells to the surface to fill the gaps left by the plates, forming a new crust
- destructive earthquakes, volcanoes
- Mid-Atlantic Ridge, Iceland
Collisional plate boundary:
1. What happens at this boundary?
2. What hazards can be found?
3. Example
- Two continental plates move towards each other. Fold mountains are created
- Destructive earthquakes
- Himalaya Mountain Range, Nepal
Conservative plate boundary:
1. What happens at this boundary?
2. What hazards can be found?
3. Example
- Two plates move past each other in opposite directions or in the same direction at different speeds
- Highly destructive earthquakes
- San Andreas Fault, California, USA
Intraplate earthquakes
Caused by stresses within a plate. Since plates move over a spheric surface, zones of weakness are creates. Earthquakes can happen in these zones
Hot spots
A plum of magma escapes the outer core and burns through all the layers of the earth. This creates a volcano. When the plates move this creates many volcanoes next to eachother
Who created the law of superposition and what is it?
Nicolaus Steno
Each layer of rock is older than the layer above it
Who came up with the supercontinent, what is it, what was it called and what did they believe was the cause of the plates moving apart?
Alfred Wegener
Once all the continents were joined together- called Pangea
The plates moved apart due to a phenomenon called ‘contenental displacement’
what is Paleomagnetism, what does it evidence and where can this been seen
Magma contains a lot of Iron
Iron particles point to magnetic north
every 300,000 years, Magnetic north flips to the opposite direction (magnetic south)
This means that newly formed magma contains iron pointing in the opposite direction
This gives evidence for sea floor spreading and can be seen along the mid Atlantic ridge
What is the main principle of the wilson cycle
Some oceans get bigger and others shrink as ridge push is stronger than slab pull
What are the 5 steps of the wilson cycle
- A continent rifts when it breaks up
- As it continues, an ocean opens, margins cool and sediment accumulates
- convergence begins (Subduction); an oceanic plate subducts, creating a volcanic and active margin
- Terrace accretion occurs (rock from two different plates stick together)
- as the two continents collide- mountains form and the ocean is closed up
How do conservative plate boundaries form earthquakes?
Friction builds as the plates move past each other
the plates become stuck, either because there is a fragment of rock in the way or because of the shape of boundary; this is called a locked boundary
eventually, the pressure that has built up due to this overcomes the strength of the fault and one plate slips past another
seismic waves radiate out from the point of movement, the focus to the epicentre
what is the benioff zone
an area of seismic activity corresponding with the slab being thrust downwards in a subduction zone; different speeds and movement of rock at this point produce numerous earthquakes- theoretically, this determines the magnitude of the earthquake
Primary waves
- caused by compressions
-quick- 8km/s - lowest amplitude
Secondary waves
- highest frequency
- faster than L waves but slower than p waves (4km/s)
- (up and down)
- highest frequency
Love waves
-highest amplitude
- most destructive
- side to side
-(1.4 km/s)
What is soil liquifaction and why does it happen
- water saturated material can temporarily lose normal strength and behave like a liquid under the pressure of strong shaking
- this is because the earthquake can increase water pressure to the point where soil particles move easily, especially in sand and silt
- often occurs in land adjacent to rivers
what are the impacts of soil liquifaction and what is an example of where soil liquifaction has happened
-damage to roads and bridges as well as telecommunication and other services
- this disrupts delivery of aid and causes large rebuild costs
- christchurch 2011- cars buried
What is a landslide
- Slopes weaken and fall
- occurs in mountainous areas
give an example of a landslide
nepal 2015- entire village buried
What plates do tsunamis occur at
- destructive; plates pushed together and then then older, denser plate suddenly slips under
- lots of pressure released and a tsunami is formed
name the key features of a tsunami (7)
-very long wavelength
- can travel thousands of kms
- approaching the shore, the tsunami speed diminishes
- moves in an eliptical motion
- water withdraws at the coast before the wave arrives
wave amplitudes increase as it approaches the shore to as much as 100ft. this is known as wave shoaling
-waves move fast at roghly 800km/hr
what is wave shoaling
the process of the waves losing volume but gaining height as they get closer to shore
what factors can increase the size of a tsunami wave
- shallow water depth near to coast
- steep gradient change of sea bed towards coastline
what factors can increase the speed of a tsunami wave
- no environmental buffer (eg. no mangrove swamps)
- deep water depth near to coast line
what factors increase the strength of a tsunami wave
- short distance travelled
- large amount of water so large volume displaced
- boundary locked for a long time ( can lead to a mega thrust earthquake causing a strong tsunami)
CASE STUDY of a tsunami
Boxing Day tsunami 2004
Boxing Day tsunami (2004) key facts
Also known as Ocean Tsunami
Largest tectonic disaster in modern history with 290,000 dead/missing
1 in 100 year event
Caused by EQ which was 9.1 on the Richter scale
What is soil liquefaction?
Water saturated sandy layers of the earth act like liquids due to the pressure created by EQ’s
Social impacts of 2004 Boxing Day tsunami
120,000 tourist workers in Thailand lost jobs
Schools and hospitals damaged so several closed
1.7mil left homeless
Disease spread due to sewage mixing with sea and freshwater
Economic impacts of 2004 Boxing Day tsunami
Ports damaged = affected trade
Tourism industry in Thailand lost $25mil per month
Infrastructure destroyed
60% fishing fleets destroyed in Sri Lanka
Environmental impacts of 2004 Boxing Day tsunami
Damaged ecosystems —> EG. coral reefs, coastal wetlands
Most vegetation and topsoil was removed up to 800metres inland
8mil litres of oil escaped from oil plants in Indonesia
Primary hazards of volcanoes: lava flows
Extensive areas of solidified lava, which can extend several kilometres from volcanic vents if the lava is basaltic and low viscosity. It can flow at up to 40 km/h.
Occurs at:
subduction zone volcano (composite)
hot-spot volcano (shield type)
Primary hazards of volcanoes: pyroclastic flow
Very large, dense clouds of hot ash and gas at temperatures of up to 600’C. They can flow down the flanks of volcanoes and devastate large areas.
Occurs at:
Subduction zone volcano (composite)
Primary hazards of volcanoes: Ash falls
Ash particles, and larger tephra particles, can blanket large areas in ash, killing vegetation, collapsing buildings and poisoning water sources.
Occurs at:
Constructive plate margin volcanoes (cinder cone, fissure eruption)
Subduction zone volcano (composite)
Primary hazards of volcanoes: gas eruptions
The eruption of carbon dioxide and sulphur dioxide, which can poison people and animals in extreme cases.
Occurs at:
Subduction zone volcanoes (composite)
Hot-spot volcano (shield)
Secondary hazards from volcanoes: lahars
Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction.
Occurs at:
Subduction zone volcanoes (composite)
Secondary hazards from volcanoes: jokulhlaups
Devastating floods caused when volcanoes erupt beneath glaciers and ice caps, creating huge volumes of meltwater. They are common in Iceland.
Occurs at:
Constructive plate margin volcanoes (cinder cone, fissure eruption)
CASE STUDY: Eyjafjallajokull key facts
Volcanic eruption
2010
Iceland
100,000Cancelled flights in worldwide for weeks (due to spreading of gas and ash cloud - cause damage to plane engines)
10mil stranded passengers
$1.7B loss in airlines revenue
$5B loss European economy
Impacts felt as far as Kenya, where export of perishable goods was impacted due to lack of transport —> $1.3mil in revenue was lost per day
CASE STUDY: Montserrat key facts
Soufriere Hills Volcano in south of Island on Caribbean Sea erupted
Huge ash clouds over next 5 years
7000 residents moved to other countries
The capital - Plymouth- was destroyed which had all of the islands services
2/3 houses and 3/4 infrastructure destroyed
Unemployment rose as tourism industry collapsed
Top heavy pop. as young ppl left due to lack of econ opportunities on island
How are volcanic eruptions measured?
Volcanic Explosivity Index (VEI):
Compares and describes the magnitude of volcanic eruptions
0-8 scale (logarithmic)
Measures - height of material ejected, duration of eruption
How are eruptions predicted?
Change in shape - magma builds pressure as it rises causing volcano to swell and change in shape
Gas - close to eruption, small of egg (sign that sulphur is being emitted from volcano - showing magma is near to surface)
Temperature (temp) - water and rock can be tested for temp which can be an indication that magma is nearer to surface than normal
How tectonic hazards are measured: Mercalli scale
Roman numerals
Composed of increasing scales of intensity ranges from shaking to destruction
How tectonic hazards are measured: Richter scale
Measures magnitude of EQ
Logarithm of the amplitude waves recorded by seismographs
Expressed in whole numbers and decimal fractions
How tectonic hazards are measured: Moment magnitude scale (MMS)
Measures size of EQ in terms of energy released
Calculated from:
- amount of slip on the fault
- area affected
- an earth rigidly factor
What is Deggs model?
Venn diagram illustrating the interception of both the hazardous geophysical event and vulnerable pop.
Define resilience
Ability to protect lives, livelihoods and infrastructure from destruction and to restore areas after a natural hazard has occurred
Define vulnerability
Ability to anticipate, cope with, resist and recover from natural hazards
Risk equation
Hazard x vulnerability
——————————
Capacity to cope
Define risk
Exposure of ppl to a hazardous event
More specifically:
Probability of hazard occurring that leads to loss of lives/livelihoods
Give 5 examples of risks
Ageing population
Low lvls of development
Unpredictability
Magnitude
Adaptation
What is the basis of the PAR model?
Root causes —> dynamic pressures —> unsafe conditions
Examples of root causes
Limited access to resources, political/economic systems
Examples of dynamic pressures
Lack of appropriate skills - eg. Training, local investment, press freedom
Examples of unsafe conditions
Fragile physical environment
Fragile local economy
Vulnerable society
Earthquakes that happen in _____ are often _____ costly as the infrastructure is more _____ and the loss of business is more _____
Rich places
More
Developed
Significant
Social impacts of tectonic hazards
Deaths
Stress on healthcare services
Spread of disease
Homelessness
Water/electricity lost
Hindered education
Economic impacts of tectonic hazards
Damage to transport (can’t get to work) (has to be repaired)
Loss of jobs (eg in tourism)
Infrastructure damage
Tourism decrease
Damage to agricultural industry
Comparison of Haiti EQ (2010) and Alaska EQ (1964)
(H) Haiti:
7.0 Mw
x1 Mercalli
160,000 deaths
$8B damage
(A) Alaska:
9.2Mw
x1 Mercalli
131 deaths
$311M damage
= less deaths in A even though A was more destructive. A was less expensive to repair as less damage due to preparation
List 7 human dynamic factors
Education - reduces vulnerability
Housing - poor housing results in collapsing and deaths
Healthcare - good emergency services means more lives saved
Income opportunities - higher income = above = better standard
Levels of development
Quality of governance
Demographics
Why is the collection of disaster data often incomplete or inaccurate?
Immediate focus is response not data collection
Hard to get data in remote areas so estimates can be inaccurate
May be subject to political bias
What is a mega disaster?
Large scale
High impact
Low probability
International responses
Require effective management
Happen rarely
CASE STUDY: Japan 2011 facts and stats
5% loss in overall GDP
Damage to Fukushima nuclear plant disabled power supply which caused radioactive releases
Toyota and Sony haltered their production
Vulnerability in Philippines
1976, midland EQ, magnitude of 7.9, causing tsunamis, killing 8000
79% economic losses came from tropical storms
17% of economic losses came from flooding
Challenges in the Philippines
Cant spend money on developing the country —> have to spend it on rebuilding
Climate means that annual tropical storms bring floods, landslides, lahars and volcanic eruptions
Why is Morocco vulnerable? 🇲🇦
Dependant on agriculture, fishing and tourism —> if a natural disaster or devastation affects environment it could leave them with nothing
Water scarcity
Food insecurity
Shoreline erosion
Moroccan economy is very exposed to impacts of climate change
Morocco facts and stats:
Pop: 10mil
UNDP human development index (HDI): 158th in world
GDP Per capita (per person): $1,179
Life expectancy: 62
Mean years in education: 5
LIC example of an EQ: Haiti
Causes - sits amongst complex plate boundaries
Dynamic factors - pop of 9.8M affected, high infant mortality
Impacts - 60% of their capital destroyed, 70% buildings collapsed, $8B damage, 230,000 deaths
HIC EQ example: New Zealand
Causes - 6.3 Richter scale, epicentre less than 6km away
Dynamic factors - developed, $10B set aside
Impacts - $20B damage, 6000 injured, 185 deaths
LIC example of EQ
2004 Indian Ocean Boxing Day tsunami
HIC tsunami example: 2011 Tohoku
Causes - large EQ hit Japan, triggering biggest tsunami in Japan’s history, 9.0 Richter scale, after just 22mins the first town was hit
Dynamic factors - strong infrastructure due to investment, good education (ppl told to evacuate and go to higher ground)
Impacts - 20,000 dead/missing, 60% =0.6 over 60 (at home, no tech —> no warning), nuclear power plant destroyed
Predicting volcanoes: gas monitoring
High sulphur levels means magma is near surface
Predicting tectonic hazards: seismometers
Monitoring the land to see if increase in seismic activity
Predicting volcanoes: thermal imaging
Can detect heat around volcano - more heat = more magma near surface
Predicting volcanoes: boreholes
Scientists can drill into volcano and test height of water level
Why is forecasting important?
It can encourage governments to enforce better building regulations in areas of high stress or create improved evacuation procedures in areas of high risk
Parks disaster response curve 1991
The Park model is also known as the disaster response curve. Its aim is to show the effects of a hazard on quality of life over a sequence of time
Define mitigation
actions and interventions that a community take to reduce vulnerability in advance of hazard
Define adaptation
Ways communities make adjustments to the risk
Eg. Being able to live with a tectonic hazard
Mitigation and adaptation can be further stratified as …..
Micro - strengthening individual buildings, ppl or structures
Macro - large scale protective measures designed to protect whole communities
Modifying the event:
Modify the loss - aid, insurance
Modify vulnerability - predictability, education
Modify event - environmental control, hazard resistant design
Modify cause - hazard prevention (only rlly possible on small scale though)
EQ modification strategy example
Strategy: public buildings and facilities strengthened to protect them from destruction. Ppl shelter in them to stay safe (hospitals, skls)
Example: Japan 2011
Tsunami modification strategy example:
Strategy: engineering systems —> displace wave energy, shore vegetation, planting mangrove swamps
Example: great Asian tsunami of 2004, fewer deaths if coasts protected
Volcanoes modification strategy example:
Strategy: spraying sea water onto lava to slow by chilling, 3D imaging of earths surface
Example: 1973 Iceland eruption
Modifying the vulnerability: public education
Good education and better public awareness can help to reduce vulnerability and prevent hazards from becoming disasters
Eg. Regularly practicing emergency procedures
Modifying the vulnerability: high tech monitoring
Accurate predictions
Allows scientists to learn more abt natural processes in the hope to predict them in advance and better
Reduces lives lost = reduces vuln
Eg. Early warning systems
Modifying the vulnerability: crisis mapping
Local ppl provide info such as where ppl are trapped under rubble
These locations are then plotted onto maps by worldwide volunteers and placed online for everyone to see
Reduces lives lost = reduces vuln
Eg. Nepal 2015 EQ ppl rode bikes using GPS trackers to find ppl
What steps do the gov. take to reduce losses following a tectonic event ?
Work with insurance companies to protect losses
Receive (and send) international aid
Implement disaster response teams
Adopt international frameworks for disaster management
Aid donors
What is it?
Helps recover and rebuild. Types: emergency, short term (st) long term (LT)
How does it reduce losses?
Emergency - provides food, clean water, shelter
ST - restoring water supplies
LT - reconstruction
Case study:
Haiti 2010. Aid straight to gov
NGOs
What is it?
Provide funds, coordinate search and rescue efforts and help develop reconstruction plans
How does it reduce losses?
Helps communities build resilience
Case study:
2005 Pakistan EQ
7.6 magnitude
NGOs provided half a million tents and safe water for 700k ppl
Insurance companies
What is it?
Helps communities recover
Provided individuals and businesses the money they need to rebuild and repair
How does it reduce losses?
Ppl aren’t as economically affected
Case study:
Japan
Communities
What is it?
Locals who are the first to respond
How does it reduce losses?
In rural communities it can take days for aid to arrive so they take recovery steps themselves
Case study:
Afghanistan EQ 2015. Mountain communities set up small groups to help with search and rescue in more remote areas
What is hyogo framework for action? (HFA)
2005 world conference on disaster reduction agreed on the Hyogo Framework for Action to prioritise DRR. set out 4 priorities:
> understand disaster risk
› strengthen governance to manage disaster risk
› invest in DRR for resilience and effective response
> ‘build back better’ in recovery, rehabilitation and reconstruction
What is the Sendai framework for disaster risk?
Organised by the UN as an attempt to provide a framework to reduce disaster risk for countries/ communities. The four priorities were:
1) Understanding disaster risk
2) Strengthening governance to manage disaster risk
3) Investing in disaster-risk reduction for resilience and enhanced disaster preparedness for effective response.
4) ‘Build Back Better’ in recovery, rehabilitation, reconstruction.
Japan (HIC) disaster management/ recovery
3rd strongest economy in world
Able to develop due to disasters. Eg. Investments in seismic engineering such as roads with absorbers for seismic shocks
Indonesia (NEE) disaster management/recovery
5.3M pop.
Located on ring of fire
Project for better housing and infrastructure
Pre disaster - represents the stage of the country or area within before disaster
