Tectonics Flashcards
What is a hazard ?
an event that threatens or actually causes damage and destruction to people, their properties and settlements
What is a natural hazard ?
Is a hazard produced by the environment
What does mitigation mean ?
Mitigation means to manage the risk, by using different precautionary actions
What is risk
The probability of a particular event happening and the scale of its possible damage
Describe the Earth structure
Core -> mantle ->
Asthenosphere -> crust
What are the two types of crust ?
Continental crust and oceanic crust
What is the lithosphere ?
The crust and upper mantle together form the lithosphere
What is the lithosphere broken down into ?
Tectonic plates
What is the name for where two tectonic plates meet ?
Plate margin
What are the three types of plate margin ?
- constructive
- destructive
- conservative
What triggers earthquakes and volcanic activity ?
The interaction between the different tectonic plates and the mantle beneath them
What are the reasons for tectonic plates moving ?
- convection currents
* slab pull and ridge push
Where are earthquakes and volcanoes located ?
Where plate margins are located
Plate margins are volcanos found on ?
Constructive and destructive
What Plate margins are earthquakes found on ?
Constructive, destructive and Conservative
Describe a constructive plate boundary
- Top part of the mantle melts and the hot molten magma rises
- The tectonic plates move apart by convectional currents. The molten magma rises in between and cools down to form a solid rock
- this forms part of the oceanic plate
- much of the magma never reaches the surface but is buoyant enough to push up at the constructive margin and form ridges
Describe a destructive plate margin
- A good example is nazca plate and the South American plate
- convection current’s close the Nazca plate to move towards the South American plate
- The Nazca plate is heavier and more dense and is forced underneath the South American plate, which creates a subduction zone and the Peru-chile trench, this subduction can cause earthquakes to occur
- The friction of the subduction, and heat from the mantle causes the plate to start to melt in the Beniof zone
- when it reaches the mantle it is almost fully destroyed, the just destroyed plate is a light mantle compared to the heavier older mantle
- this means the light mantle can often be pushed upwards out of the volcano and cause the volcano to erupt
Describe convection current’s
- The earths radioactive core heats the mantle and it rises in plumes to the earths crust
- when it reaches the crust, which creates a hotspot the cooler rock in the cell flows back down to the core while dragging the plate as it goes
What is seismic?
Vibrations of the Earth’s crust
What is Tephra ?
Rock fragments and particles ejected by a volcanic eruption
What is the asthernosphere ?
Region below the lithosphere where the rock is less rigid and transmit seismic waves
What is the subduction zone ?
Where one plate moves under another and is forced into the mantle
What is Basalt ?
A dark fine grained volcanic rock
What is the epicentre ?
The point where the focus of the earthquake wave hits the surface
Describe a Conservative plate Boundry
- To tectonic plates move parallel to each other.
- either in the same direction or opposite directions
- this causes friction and pressure
- which when the pressure is released causes an earthquake
What are the four reasons why people continue to live in hazardous areas ?
- geothermal energy
- farming
- mining
- tourism
Describe geothermal energy
- in volcanically active area geothermal energy is a major source of electrical power
- Steam is heated by hot magma and boreholes are created to harness the heated steam which turned turbines at power stations
- it is renewable, reliable and causes no pollution
Describe farming
- weathering of lava releases minerals and leaves behind extremely fertile soil, rich in nutrients
- this soil can be used for farming
- volcanic soils support 10% of the worlds population, and only 1% of the world has this soil
Describe mining
- dormant and active volcanoes in mined for valuable minerals
- miners earn six dollars per day (morning on the coffee plantation)
- however is very dangerous
Describe tourism
- tourists visit volcanoes the spectacular views and hot springs
- more than 100 million people visit volcano sites every year
- locals can get money for selling souvenirs and tours
How can the risks of earthquakes and volcanic eruptions be reduced ?
- monitoring and prediction
- protection
- planning
Describe monitoring and prediction for earthquakes
- sensitive seismometers are used to sensor foreshocks
- seismologists use radon detection devices to detect radon gas in the soil and ground water, which escapes from cracks in the earths surface
Describe how planning can reduce the risks of earthquakes
- repairing emergency aid supplies, how they distributed and where are evacuation centres will be saves lives
- furniture and objects can be fastened down so they are secure from toppling over
- residents can learn how to turn off the mains gas, electricity and water supplies to the properties
Describe how protection can reduce the risk of a earthquakes
- designing buildings and strengthening roads and bridges to with stand earthquakes provides protection
- however these are very expensive and usually earthquake prone areas are LIC
Describe how monitoring and prediction cannot reduce the risk of volcanic eruptions
- thermal heat sensors detect change in the temperature of the volcano surface
- satellites monitor ground changes in the volcano surface
- seismometers measure small tremors
Describe how protection can reduce the risks of volcanic eruptions
- it is very hard to protect against volcanic corruption is as buildings cannot be designed to with stand lava flows
- people just have to be evacuated to a safe location
Describe how planning can reduce the risk of volcanic eruptions
- evacuation plan is created
- authorities and emergency services need to prepare emergency shelter, food supplies and form of evacuation strategy
- residents can be educated about preventing unnecessary injury and loss of life, by being taught to cover their eyes nose and mouth to prevent irritation by gas fumes
Primary affects of Icelands volcanic eruption
- volcano ejected 250 million m³ of tephra
- it ejected lava up to 150m into the air
- molten lava flowed 2.5 miles from the volcano
- it’s highest plume reached 8km in height
- The eruption caused ice to melt, this quickly cooled the lava resulting in abrasive glass particles
Key facts about Icelands volcanic eruption
- volcano was called eyjafiallajkull
- it erupted on the 14th of April 2010
- stop erupting on 21st May 2010
- Iceland is located on the mid Atlantic Ridge. The North American and Eurasian plates move apart causing magma to rise and erupt
Secondary social Impacts of icelands volcanic eruption
- 20 countries closed there air space, for 6 days, 100,000 travellers were affected
- 500 farmers were evacuated from the area
- high sulphur dioxide levels lead to breathing problems
- 800 local people were evacuated
- Schools in southern Iceland closed
Secondary economic impacts of Iceland volcanic eruption
- Airlines lost money, British airways lost $30 million a day
- Kenyan farmers were losing $2 million a day as they couldn’t transport the flowers to Europe, which is 1/3 of their market
- ferries, car rentals, taxis and buses benefited
- travel agents in the UK lost £6 million a day
- loss of income for Icelandic farmers, because farming was difficult because of an ash layer
Secondary environmental effects of Iceland volcanic eruption
- The ash had a high fluoride content, this contaminated streams and water.
- sudden melting of glacier caused flooding not nearby rivers, and one road was washed away
- there were ash falls deeper that 10cm
- nutrients released from ash into soil
Response to volcanic eruption in Iceland
- send out emergency services
- get the homes insured
- Store food and water and first-aid
- evacuated people to safe zones
- provide knowledge of what’s happening
Key facts of the Japanese earthquake and Tsunami
- happened on 11 March 2011
- reached 9 on the Richter scale
- 15,850 people killed
- 5895 injured
Secondary effects of Japan’s earthquake
- 39 m Tsunami reach 10 km inland, which caused flooding
- shipping was disrupted
- agriculture was effected
What was the cause of the Japanese earthquake and Tsunami
Movement between the Pacific and North American plate
Impacts of the Japanese earthquake and tsunami
- 15,850 people killed
- buildings destroyed
- 5,895 people injured
- flooding of Sendai which is a low-lying city
- soil liquefaction
- 3-4% of rice production was devastated
- 2m waves hit the coast of Chile on the other side of the Pacific Ocean
Response to Japan’s earthquake
- £500 million was put into upgrading earthquake measurement equipment
- Japan self defence carried out a massive upgrade training drill called “alert 2008”
- providing food and blankets to people who lost their homes
- they now have building regulations to make sure they are earthquake proof
- highway six rebuilt in six weeks
Key facts about Nepals earthquake
- happened on 25 April 2015
- 80 km north-west of Kathmandu
- 7.8 on the Richter scale
- 9000 people died
- 1/2 million people left homeless
What was the cause of the Nepal earthquake ?
It occurred because of the subduction of Indian plate underneath the Eurasian plate
Effects of Nepals earthquake
- killed 9000 people and injured 23,000
- 7000 schools were flattened due to it being a school day, this increases the death toll
- 1/2 million people left homeless
- 1/3 of the population were affected by the earthquake
- people waited up to 7 days without water
- it triggered an avalanche on Mount Everest killing 19 people
What were the responses and management of Nepals earthquake
- Nepal doesn’t have insurance so they got no money back from the earthquake
- Technology is bad meaning building are unstable and help is hard to get
- they waited 7 days without water
- Nepal relied on aid which is hard to distribute because of inaccessible rural area
- disease set in
