Tectonics Flashcards
What is plate tectonics?
The theory that describes movement of the earth’s surface (crust).
Explains fold mountains distribution, earthquakes, volcanoes and continental drift
Earth structure from outside to inner
Crust
Mantle
Outer core
Inner core
Features of each layer of earth
Crust = made of tectonic plates, solid layer we live on
Mantle = thickest layer (2900km), solid partially melted, divided into upper + lower and heat within these drives convection currents
Outer core = made up of liquid iron and nickel, between 3500-4000 degrees
Inner core = hottest 4000-4700 degrees, made of solid iron and nickel (under so much pressure they can’t melt)
Why is the earth unstable (ie why do the plates move)
Radioactive decay in core heats magna
Magna rises as it becomes less dense and spreads out
Magna cooks and sinks
Cycle of convection cell restarts
These convection currents in mantle allow the plates to move
Two types of plates?
Oceanic
Continental
Oceanic plate features
More dense Millions of years old 8 km deep Made of basalt rock Eg Pacific plate
Continental plate features?
Less dense Billions of years old 65 km deep Made of granite Eg Euroaisan plate
Different types of plate boundaries?
Conservative
Constructive
Destructive collision
Destructive subduction
Conservative plate boundary ?
Plates slide past each other
High magnitude EQs if plates stick
Constructive plate boundary?
Two plates move away from each other and magna rises to fill the gap
Volcanos
Low magnitude, high freq EQs
Midatlantic ridges form
Destructive plate boundary subduction?
Oceanic move towards continental plate but is forced downwards because it is much heavier
Volcanos
High mag EQs
fold mountains
Destructive plate boundary collision?
2 continental plates collide and are forced upwards
Fold mountains
High mag EQs
What are earthquakes?
Vibrations and energy released by plates moving, caused by earth movements at plate boundaries and fault lines
When do EQs happen?
Conservative : Two plates can't move past each They become locked Friction causes pressure to build up SUDDENLY power is released and they jolt into new position This causes seismic waves (The vibrations = EQ
What is the epicentre
The city on top of the EQ
What is the focus ?
The point in the ground where the EQ happens
What is magnitude? What scale is it measured by?
Size of earthquake at source to see how much seismic energy has been released
Richter scale used
What is intensity? What scale measures it?
It’s the subjective measurement to the severity of the earthquakes shaking
Mercalli scale used
MEDC vs LEDC EQ case study?
Haiti 2010
Vs
Christchurch 2011
Cause/features of Haiti 2010?
- It was caused by a conservative fault between the North American Plate and the Caribbean plate.
- Strike slip earthquake, magnitude 7 with its epicentre being 15 km away from the capital of Haiti, Port-au-Prince. It had a depth of 8km below the surface, high intensity
- Had an intensity of 9, considerable damage to all structures, ground cracks, broken underground pipes
Causes/features of Christchurch 2011?
- New Zealand lies on a conservative fault (Alpine fault) between the Australian and Pacific plate: it is susceptible to powerful earthquakes.
- Lies on the Pacific ring of fire meaning that there is a high amount of seismic activity occurring, it was a strike slip earthquake, 6.3 magnitude, 3 miles of Christchurch
- Liquefaction played a large role in the damage dealt from this earthquake
Social impacts of Haiti EQ?
180,000 homes destroyed
1.5 mil homeless
230,000 died
5000 schools destroyed
Economic impacts of Haiti?
180,000 homes destroyed
$11.5 bil rebuilding cost (60% of GDP!!!!!!)
damage to textile factories = mass unemployment
Environmental impacts of Haiti?
19 million m^2 of rubble
Contaminated water
Immediate Haiti responses?
- General aid:
- UN flash appeal for $1.5 billion
- Enough emergency shelter has been provided for 1.9 million people
- 2000000 people have received cash or food for public work
- DEC appeal has raised £101 million
- Latrines have been built, clean water and over 100000 medical consultations provided
Long term Haiti responses?
Education about earthquakes army presence to restore order Long term shelter Rebuilding roads Relocating people
Christchurch social impacts?
185 deaths (115 from one building collapse)
220,000 homes affected
13 schools would close and the permanent migration of 50000 of Christchurch’s residents
Christchurch economic impacts?
70% of CDP has to be rebuilt
Damaged Lyttleton port where imports and exports trade is done
Will cost $30 billion (10% of NZ’s gdp)
Immediate responses to Christchurch?
Evacuation
Relocation
Rebuilding
Long term responses to Christchurch?
Careful EQ monitoring
More alert emergency services
Better building standards (eg 1 building collapse killed 115 out of total 185 who died)
Why did Christchurch suffer so much less damage than Haiti?
- It is an MEDC- stronger buildings with better prediction and preparation and less densely populated due to no slums, Christchurch only has a population of 350000
- Deeper earthquake, 4 km further down
- Better prediction/ protection because of it being a richer country
How do fold mountains form? Examples?
Fold mountains form along both destructive and collision plate boundaries.
They form when two plates with landmasses on them move towards each other.
The plates push layers of accumulated sediment in the sea into folds between them.
This becomes a fold mountain range.
Most fold mountains continue to grow as the plates constantly move.
Examples: the Himalayas (Asia), Andes (South America), Alps (Europe)
Case study of how people use one range of fold mountains
The Andes
How do people use the Andes?
Farming
Hydro electric power and industry
Mining
Tourism
How people use Andes for farming
- Valley floor is used for farming as the land is flat, fertile from minerals coming of the mountains, has shelter from winds, and has easy access
- Traditional farming is farming Alpacas in the Andes, pipes and cable cars are used to transport the produce down the valley
How people use fold mountains for mining?
- Easy access to find materials which are usually found a lot lower from the surface, deep earth metals pushed up with squashed layers of rock make them.
- Copper and tin mines are found in the Andes
How people use Andes for hydroelectric power and industry?
Steep slopes, high precipitation and summer melts mean it is good place to make hydroelectric power
• Narrow valleys are easy to dam and 60% of the energy from Switzerland comes from this
• Up to 1800m there are coniferous forests for timber industry, soft woods are used for fuel, building and paper
How people use fold mountains for tourism?
Many resorts like Chamonix opened for skiing; roads, tunnels, avalanche shelters are implemented.
• Attracts skiers, walkers + climbers attracted by the beautiful scenery, winter sports facilities, good communication and alpine climate.
• This generates £100000 million every year
When are volcanos formed? How does magma rise?
Volcanoes are formed along two types of plate boundary: destructive and constructive. Volcanoes occur where molten rock (magma) comes to the surface of the earth.
The magma rises to the surface through cracks in the crust called vents
Types of volcano
Shield
Composite
Features/structure/example of composite volcano
Composite volcanoes are the most deadly of volcano types.
They are made of alternate layers of ash and lava and have steep sides built up by eruptions of intermediate viscosity andesitic lava and explosive tephra.
Often the lava cools creating a plug which blocks the vent resulting in a huge explosion blowing out the plug
Eg Mount St. Helens in Alaska
Features/structure/example of shield volcano
When lava is runny and thin it can flow a long way before cooling and solidifying, this causes shield volcanoes to have gentle slopes and wide bases built almost entirely of low viscosity basaltic lava flows.
Shield volcanoes are the largest of the three types. They have low wide come and gentle slope
The eruptions are generally non explosive due to the low silica content and may last for years
Casestudy of volcano?
Eyjafhallajokull iceland volcano
Cause of Icelandic volcano?
- It sits on the Mid Atlantic Ridge in the North Atlantic ocean, on the constructive plate boundary of the Eurasian and North American plates, making it have volcanic activity
- Iceland itself is a hot spot itself (high amount of Volcanic activity) where there is a large amount of melting rock in the mantle
- Cold melt water cooled the magma quickly causing it to fragment explosively into large volumes of very fine ash which were ejected high into the atmosphere, known as a phreatomagmatic eruption
Short term impacts of Icelandic volcano?
- 150m ice cap melted- major flooding in Iceland and 800 people were evacuated
- 20 farms destroyed by the ash and flooding
- The fine ash was a danger to the airplanes because of the high silica content, melting into a glassy substance when exposed to the heat of the engine, damaging it; therefore, airspace was closed over Europe, 17000 flights were cancelled. This lead to a loss of $2 billion dollars.
- Damaged poorer countries like Kenya who needed air drops from European countries.
Long term impacts of Icelandic volcano?
It could boost Iceland’s tourist industry with the new visitor centre
• Fine ash silted the rivers and caused blockages a year on, forced government to pay to dredge rivers
Responses to Icelandic earthquake
- EU funded a project called FutureVolc to install sensors for analysis
- The monitors can detect minute movements or tremors within the ground, gas emissions
- Flight companies are looking to test systems which will enable the planes to detect and avoid ash clouds because there was a huge outrage to the long ban on flying
What is a super volcano?
- They emit at least 1000km^2 of material, 8 on the Volcanic explosity index (scale runs from 1-8)
- Instead of the cone shape they have depressions called Calderas
Casestudy of super volcano?
Yellowstone supervolcano USA
Local impacts if Yellowstone exploded
- It will destroy everything within a 500km radius
* Deposit ash from 1-5m deep 1000km away from the volcano
National impacts if Yellowstone exploded
- Ash deposits
- Could trigger Tsunamis which could travel up to 5000km
- Poisonous gases contaminate water supplies
Global impacts if Yellowstone exploded?
- Buried crops, damage to health from gases and ash, climate change
- Ash would block out sun, creating a Volcanic winter where temperatures would fall by 5-10 degrees
What is a tsunami?
Aka seismic sea waves
Can be caused by landslides, underwater volcanos and more commonly underwater EQs
Case study of a tsunami
Japan 2011
Causes of Japan 2011?
- It was a triple disaster: a earthquake, Tsunami and a nuclear disaster
- A magnitude 9 earthquake was created by the subduction fault line between the North American and Pacific plate. It was a mega thrust earthquake which displaced a large amount of water, creating a tsunami which rose up to 10m in height.
- 100km east of Sendai
Primary effects of Japan?
- Coastal settlements, like the city of Rikuzentakata and the port of Minami-Sanriku were destroyed whilst Tokyo was only lightly affected by the Earthquake
- The town Sendai, with a population of 100000 was destroyed.
- 200000 buildings were damaged by both the earthquake and the Tsunami
- 16000 dead, 3000 missing
- Expected cost adds up to 16.9 trillion yen, the most costly disaster ever (but less than 10% of Japan’s GDP
- Flooded 500km2
- Created a reactor malfunction in the Fukishima power plant, lead to mass displacement and damage to the environment
- Ground was lowered by 1m
- 700 aftershocks hampered reliefs
- Electricity cut off to 6million homes
- Freezing winter also hampered relief efforts
Immediate responses to Japan 2011?
- 100000 soldiers from Japan’s Self Defence forces was mobilised to establish order and rescue work
- Global relief effort from many countries
- Searching for survivors
- Exclusion zone erected by Fukushima power plant, iodine tablets distributed to prevent radiation sickness
- Because of educated population, many escaped buildings
Long term responses for Japan tsunami?
Not much because Japan is one of the best defended countries against earthquakes, with yearly earthquake drills and general education, 10 m sea walls and etc
• Looking at strength of coastal defences
Japan’s scheme before the disaster
Predict
Prepare
Protect
How did Japan predict?
• Has its own hazards agency, Japanese Meteorological agency which detected earthquake and sent televised and text warnings to relevant areas, well equipped
How did Japan prepare?
- Televised messages for both, automated shutdown of nuclear power plant
- They had 20 minutes to get to safety before the earthquake
- Soldiers and emergency arrived quickly
- Criticised for not accepting aid quickly
- Earthquake drills
How did Japan protect?
- 40% of Japanese coast had 10m high sea walls
- Buildings designed to sway and not crash
- Flood gates and strict planning control
Evaluate Japan’s predict protect prepare plan
Good but 10m high walls weren’t effective as the ground sunk meaning they didn’t cover the height they were thought to
