Tectonics Flashcards
Where are earthquakes found?
They are found at plate boundaries where there are build ups and releases of pressure as plates collide or diverge.
Where are volcanoes found?
Volcanoes are usually found at plate boundaries:
Around the edge of the Pacific Ocean
Down the centre of the Atlantic Ocean
In Southern Europe
Down the east coast of Africa
They may also be found in on hotspots
The Ring of Fire around the Pacific Ocean has the biggest number of volcanoes
What is the structure of the earth?
Inner core, outer core, mantle, crust
What happens at constructive boundaries?
Two plates move apart and magma rises to fill the gap
Volcanoes and earthquakes may occur
Mid-Atlantic Ridge
What happens at destructive boundaries?
Found where a continental plate meets an oceanic plate (or oceanic/oceanic)
The oceanic plate subducts beneath the continental as it is more dense
The oceanic plate melts due to friction caused by movement of the plates (subduction)
The melted plate is now magma
Magma rises through gaps in the continental plate
If it reaches the surface, the liquid rock forms a volcano
Nazca-South American
What happens at conservative plate boundaries?
Occur where two plates slide past past each other at a fault
Pressure builds up along the fault until one play jerks past the other causing an earthquake
San Andreas Fault (North American and Pacific)
Collision zones
Where two continental plates move towards each other and collide
Neither can sink so they’re folded up into fold mountains
Earthquakes form
Indian plate colliding with Eurasian plate (Himalayas)
Why do plates move?
Due to the convection currents in the Earth’s mantle. They are driven by the heat produced by decay of radioactive elements and heat left over from the formation of the Earth
Impacts of earthquakes
Destruction of buildings Interruption of water supplies Breakage of sewer disposal systems Loss of public utilities such as electricity and gas Flood from collapsed dams Release of hazardous materials Fires Spread of chronic illness (typhoid) Loss of people Tsunamis Landslides
Impacts of volcanic eruptions
Deaths Damaged crops Destroyed buildings Homelessness Blocked roads so emergency vehicles cannot get through
Hazards associated with earthquakes
Ground shaking Surface faulting Ground failure Soul liquefaction Landslides and rockfalls Debris flows and mudflows Tsunamis
Why do people live in earthquake prone locations?
Poverty: Some people are very poor and are forced to live on marginal land that is very vulnerable to the impacts of earthquakes:
Inertia: Some people have lived in earthquake zones although their life an are unwilling to move
Infrequency: Major earthquakes happen relatively infrequently so some people are prepared to take the risk and don’t think that one will occur in their lifetime.
Overpopulation: Some countries are very densely populated so people are forced to live on dangerous and marginal land.
Building Design: Building design has improved and now people are confident that their house or workplace will withstand strong earthquakes.
Education and preparation: Many countries practice earthquake drills and evacuation and prepare their houses so feel confident that they will know what to do in an earthquake.
Economic Opportunities: Many tectonically active locations have good resources and locations e.g. next to the sea. Because of this there are many job opportunities which people move near to take advantage of.
Hazards associated with volcanic activity
Pyroclastic flows: giant clouds of ash and gas which travel very fast and destroy everything in their path
Lava flows: bury and incinerate anything in their way though they travel slowly
Lahars: ash and gas melt the snow and mix with it to form fast moving mudflows which bury anything in its way
Ash clouds: falling ash can destroy buildings and cause injuries and cause problems for air travel
Lava/volcanic bombs: pieces of semi-molten rock thrown out of volcanoes which can cause fires
Poisonous gases: carbon monoxide and sulphur dioxide are poisonous to humans and add to global warming
Why do people live near volcanoes?
Potential for geothermal energy: water is heated by geothermal steam and used to produce electricity
Monitoring and prediction: scientists monitor seismic activity and produce hazard maps
Crystallisation: lava can be crystallised to form minerals like gold, silver, diamonds, copper and zinc so they are great places to mine
Fertile soils: thousands of years of physical and chemical weathering has produced fertile soils to grow a range of products (olives, fruits, vines, nuts)
Tourism: hot springs, mud baths, spas, scientific interest, skiing in winter
How to deal with earthquakes and volcanoes?
Better forecasting
Better building design and emergency procedures
Producing hazard maps to reduce settlements being built in those places
Exclusion zones: evacuating people in the most dangerous areas
Looking at seismic activity in the past to recognise trends
Noting strange behaviour in animals
Recording change in electrical conductivity
Cooling lava in volcanoes to solidify rock before it does damage
