Tectonics Flashcards
What happens when two oceanic plates pull apart?
- Pull apart due to convection current and bulging up of magma which pushes plates apart and forms cracks
- Constructive plate boundary
- Runny basalt lava rises up and forms shield volcanoes
- Mid Atlantic ridge
- North American Plate and Eurasian Plate
What happens when two continental plates pull apart?
- Rift basin e.g Great Africa Rift Valley
- Magma bulges up and pushes plates apart and causes cracks where gases etc rise and volcanoes form
Give an example of destructive plate margins
Where Nazca Plate and South American Plate meet- Peru Chile Trench
Fold mountains eg. Himalayas- two continental- Indo-Australian and Eurasian Plate
Stratovolcano eg. Nevado del Ruiz
Give an example of transform plate boundary?
North American(1cm/y) and Pacific Plate(6cm/y)
What are the features of a volcano?
- VENT: main outlet for magma to escape
- MAGMA CHAMBER: collection of magma under crust
- CONDUIT PIPE: where magma rises up to surface
- PARASITIC CONE: mainly in stratovolcanoes, when main chamber is clogged, magma breaks through side
- SIDE VENT: smaller outlets for magma
- FLANK- side of volcano
What is a pyroclastic flow?
Avalanches of red hot gas and ash and volcanic bombs p to 700kmph
What is a lahar?
- Hot fast moving mudflows down the side of volcanoes.
- Ice melting created large volumes of water which sweeps down volcano picking up debris and soil and its density/ overall volume increases to form hot mudflows
How do hotspot volcanoes form?
When crust moves along over an especially hot part of mantle close to crust- plume which stays in the same place and rises to form volcanoes.
Eg. Kilauea in Pacific Ocean- Hawaii
What is a dormant volcano?
One that hasn’t erupted in 10,000 years
What is an active volcano?
One that has had an eruption in the past 10000 years
How do you predict volcanoes?
- Satellites use infra red to monitor changes in thermal energy near volcano as magma rises
- Remote sensing- satellite sensors detect sulphur dioxide emissions(main component of volcanic gases)
- Seismometer- detect vibrations as magma rises
- GPS- to see minute changes in position of crust
What are the primary effects of a volcano?
- pyroclastic flows
- nuées ardentes
- Homes destroyed- people dead
- Businesses destroyed under as lava eats through it
- Destruction of crops and farmland
- Damage water supplies
What is a nuées ardentes?
Turbulent cloud of gas, ash, and rock fragments flowing close to the ground after violent ejection from a volcano.
What is a natural hazard?
It is a naturally occurring event that has the potential to affect humans and their property or the environment (in a negative way).
Tectonic hazards and Climatic hazards
What are the primary effects of an earthquake?
- Collapsing bridges/railways etc
- Collapsing buildings
- People injured/killed
- Gas pipes burst
- Water/electricity supply disrupted
What are the secondary effects of earthquakes?
- Landslides
- Tsunamis- sea bed jolts up and creates massive waves which slow down but increase height up to 30m
- Leaking gas leads to fire
- Leaking water = contaminated water flood= cholera
- Can’t get aid/supply in if transport is down
- Job lost as businesses or farmland destroyed= financial loss
How to predict earthquakes?
- Look at patterns for past eruptions- computer models: seismic gap theory
- Look at smaller eruptions happening nearby asses if it will come here
- Monitor radon gas emissions
- Cracks form in the ground
How to reduce impact of earthquakes?
- Warning systems to warn people to prepare = less panic
- Building planning to not build where the earthquake is most severe
- Having evacuation points in towns/ shopping malls etc
- Emergency service trained to evacuate efficiently
- Better building codes so they withstand earthquake
- Earthquake proof roads/ bridges
- Try to predict earthquake
- Emergency supply kits
Why are earthquakes more severe in LEDCs?
- No building codes to withstand earthquake
- Less trained people to help evacuate or treat injured- more deaths
- Not enough technology to predict and or give out warnings- rural areas have no network coverage
- Roads/ railways built of inferior quality so damage more easily so evacuations or emergency aid not able to be given
Why do people continue to live in earthquake prone areas?
- Family links
- No money to move
- Good climate
- Insurance covers losses- can afford to rebuild
- MEDCs can protect people in earthquakes- strong buildings, good emergency services etc
- Lots of jobs in that area
- People may not believe earthquakes will happen again there
How are buildings made to withstand earthquakes?
- Base isolators for shock absorption
- Weights to sway building side to side with movement of ground
- Walls reinforced with steel so they don’t shatter as easily
What are the secondary effects of a volcano?
- Minerals deposited by lava create fertile soils for farmers= higher yield = more income
- Tourists attracted = more money for economy
- lahars caused by pyroclastic flows
- Loss of buildings = homeless/jobless
- Food water shortages
- Roads/ railways blocked so supplies can’t get in
how to reduce impact of volcanoes?
- Predict using modern technology = more accurate
- If you can predict, you can evacuate faster
- Building planning to not build in danger areas
- Aid from foreign countries and government
Why do people live near volcanoes?
- Tourists= more jobs= more money
- Fertile soils = more crops can be grown= more money
- Geothermal energy for homes
- Mining for rich minerals
What is the Richter Scale?
It is a base 10 logarithmic scale measuring the magnitude of an earthquake. Each value is 10 times more than the previous one.
What is magnitude?
The size of the earthquake depending on the amplitude of the seismic waves. It is the amount of energy released.
What is the intensity of an earthquake?
Intensity refers to the extent of damage done to people and infrastructure etc
What is the epicentre of an earthquake?
It is the point above the focus on the surface of the earth
What is the focus(hypocentre)?
The point underground where the earthquake/ fault movement actually happened
