A2: Tectonic Hazards Flashcards
Section A: Chapter 2 [2nd Edition Text Book]
What is the Earth’s structure?
Crust, then mantle, then outer core, then inner core.
What are the different crusts?
Continental crust: thicker but less dense and much older.
Oceanic crust: thinner but more dense and much newer
Explain the theory of convection.
Hot magma from the core rises until it reaches the crust, it cools down, spreads and sinks back down into the magma. This forms a convection current that pulls the tectonic plates.
Explain the theory of ridge push.
Ridge push: on constructive plate margins, ocean ridges form high above the ocean floor. Under these ridges, the mantle melts and rises causing the he crust to move apart, Magma fills the gap and cools down, forming new oceanic crust.
Explain the theory of slab pull.
On destructive plate boundaries, ridge push causes this to happen as it causes oceanic crust to collide with continental crust. The oceanic crust is denser, so is subducted and destroyed under the high pressure and temperature.
What happens at constructive plate boundaries?
Ridge push happens, so plates move apart. The cooling magma forms new plates. A few times, the magma pushes up the crust and erupts. Over many eruptions a shield volcano forms. No earthquakes as there is no friction against the plates.
What happens at a destructive plate boundary?
Slab pull happens here, so the oceanic crust is subducted and destroyed under high temps and pressure - this forms new magma that heats up and rises again. This can erupt producing composite volcanoes. There is friction as the oceanic plate is subducted, so earthquakes can occur.
What happens at a conservative plate boundary?
Plates move in opposite directions, or in the same direction but at different speeds. The faults rubbing against each other create a build up of friction. This friction will eventually be overcome by the force moving the plates forwards creating a forceful push - which will create a powerful earthquake. No volcanoes form as no plate is being created or destroyed.
Describe a shield volcano.
Gently sloping and and built up in layers. Eruptions are more gentle but frequent and the lava is low viscosity.
Describe a composite volcano.
Cone shaped and steep sided, built up in may layers. More explosive eruptions but less frequent. due to built up pressure of trapped gas, and the lava is more viscous.
When did the Earthquake in Nepal take place?
25th of April 2015
What was the magnitude of the Nepal Earthquake?
7.8
Where was the epicenter of the Nepal Earthquake?
Barpak - 8km from Kathmandu
What were the primary effects of the Nepal earthquake?
- Pharaha tower destroyed (historical site) - so loss of tourist destination
- 8841 killed, 700 000 injured
- 1 million homeless
- 26 hospitals destroyed
- 25% of all schools destroyed
- 2nd Earthquake of 7.3 magnitude.
What were the secondary effects of the Nepal earthquake?
- Decrease in tourism - which was 8.9% of the GDP and provided 1.1 million jobs.
- Farm land and crops destroyed - 2/3 of people relied on farming
- Starvation due to early monsoon season, and rice storage/ seeds destroyed
- Avalanche on Mt Everest, 19 killed
- Sewage pipes broken, disease spread.
What were the immediate responses to the Earthquake?
-Disasters emergency committee provided $126 Million in aid.
- Red Cross gave 225 000 people temporary shelter
- UN and WHO sent medical supplies to most affected areas.
- Sherpas used to hike mountains to supply relief aid
What were the long term responses to the Nepal earthquakes?
- OCHA gave $247 Million in aid
- Heritage site opened in June 2015
- August 2015 Mt. Everest reopens and route remade.
- Climbing permits extended to promote tourism
-November 2018: 34% of homeless are still in shelters.
When did the earthquake in Italy take place?
6th April 2009
Where did the earthquake in Italy take place?
L’aquila
What was the magnitude of the Italy earthquake?
6.3
What were the primary effects of the Italy earthquakes?
-10 000 to 15 000 buildings collapsed.
- L’Aquila University destroyed
- 308 people injured, 1500 injured
- 67 500 homeless
- Cultural and historical monuments: Basilica, museum, Porta Napoli destroyed.
- Hospital damaged and patients evacuated
What were the secondary effects of the Italy earthquake?
- Decrease in number of students at L’Aquila university
- Lack of housing so rent and house prices increases
- Reduced tourism and business
- lack of healthcare and treatment
- aftershock triggered landslide and rockfall
- Pipe burst triggered mudflow.
What were the immediate responses to the Italy earthquake?
-Hotels gave shelter to 10,000 people
- 40,000 tents given out
- Train carriages used as shelter.
- Italian Red cross raised £171,000
- L’Aquila declared a state of emergency; speeding up international aid
EU granted $522.9 million in aid.
What were the long term responses to the Italy earthquake?
-Torchlit procession to honor the dead
- Residents of L’Aquila exempt from paying tax
- Students given free transport and exempt from paying university fees for 3 years.
How can prediction be used to manage tectonic hazard risk?
-Seismologists use radon detectors to measure escaping radon gas
- seismometers used to sense tremors.
- Earthquakes are timed and mapped so patterns can be spotted
How can protection be used to reduce tectonic hazard risk?
what’s the problem with this?
-designing roads and buildings to withstand the force of earthquakes
It’s expensive and not possible to adapt existing buildings. Also, the aim of mitigation is to reduce death and injury - the buildings will still be damaged and have to get repaired.
How can Planning be used to reduce the risk from tectonic hazards?
-Furniture can be fastened down
- people can learn to turn off gas and electrical and water supply
- people can learn to calmly and quickly act so aid can be affective quicker
- emergency aid can be planned; where/ how to distribute supplies and store them
- practice drills and safety checklists.
Why do people still live in areas with risk of tectonic activity?
- Geothermal energy near volcanos
- Farming (fertile land)
- Mining Sulphur from sulphuric lakes to be sold
- Tourism (volcanic sites get over 100 million people per year)
- Family, friends, feelings
