1-A Tectonic Hazards Flashcards
What is the plate tectonics theory?
Tectonics plates move because of convection currents in the Earth’s mantle. These are driven by the heat produced by the decay of radioactive elements inside the Earth.
How is the distribution of earthquakes and volcanic eruptions related to plate margins?
1) They are found on both land and sea (the Ring of Fire, band of earthquakes and volcanoes which circles the Pacific Ocean)
2) Not all lie on plate margins. Some also occur in the middle of plates, called ‘hot spots’; the Earth’s crust is particularly thin. (Hawaii has formed due to ‘hotspots’)
What occurs at a constructive plate boundary?
Earthquakes and Volcanoes can be formed
1) Plates move apart
2) Magma wells up to fill the gap
3) New crust is formed
4) Volcanoes are formed
E.g. Eurasian plate and the North American plate move apart to form the mid-Atlantic Ridge
What occurs at a destructive plate boundary?
Earthquakes and Volcanoes can be formed
1) An oceanic and a continental plate move together
2) The oceanic is forced under the less dense continental
3) Friction causes the melting of the oceanic plate (may trigger earthquakes)
4) Magma rises through cracks and erupts onto the surface
E.g. Nazca plate forced under South American plate
What occurs at a conservative plate boundary?
Earthquakes are formed
1) Plates slide past each other in opposite directions, or in the same direction but at different speeds
2) Friction is eventually overcome and plate slips past in a sudden movement
3) Shockwaves created produce an earthquake
E.g. San Andreas Fault in California
What are the primary effects of earthquakes?
- Buildings and bridges collapse
- People are injured or killed
- Electricity cables, gas and water pipes are damaged
What are the secondary effects of earthquakes?
- Earthquakes can trigger landslides and tsunamis, which causes more primary effects
- Leaking gas can be ignited, starting fires
- Peoples are left homeless and could die
What are the immediate responses of earthquakes?
- Rescue people trapped by collapsed buildings and treat injured people
- Recover dead bodies to prevent disease spreading
- Set up temporary shelters for people whose homes have been damaged or destroyed
What are the long term responses of earthquakes?
- Re-house people who lost their homes
- Repair or rebuild damaged buildings, roads, railways and bridges
- Reconnect broken electricity, water, gas and communication onnections
What are the primary effects of a volcanic erruption?
- Buildings and roads are destroyed by lava flows and pryoclastic flows
- People and animals are injured or killed by lava, pyroclastic flows and falling rocks
What are the secondary effects of a volcanic erruption?
- Mudflows form when volcanic material mixes with water - they cause more destruction, death and injury
- Flooding can be caused by hot rock, ash and gas melting ice and snow.
- Transport networks are blocked or destroyed so aid cannot be sent
What are the immediate responses of a volcanic erruption?
- Provide food, drink and shelter for evacuated people
- Treat people injured by the eruption
- Rescue anyone cut off by damage to roads or bridges.
What are the long-term responses of a volcanic eruption?
- Repair and rebuild if possible, or resettle affected people elsewhere
- Repair and reconnect infrastructure
- Improve, repair and update monitoring and evacuation plans
Why do some people live in areas at risk from tectonic hazards?
- They have always lived there - moving away may mean leaving friends and families
- They are employed in the area and if they move, then they will have to find new jobs
- They are confident of the support services provided by the governments
How can predicting a tectonic hazard reduce the risk?
- Earthquakes are hard to predict, but scientists can monitor plate movements to understand which areas are at risk
- Volcanic eruptions can be well-monitored. This can give people time to evacuate when a volcano is going to erupt
