Topic 2 - Tectonic Hazards Flashcards
Unit 1: Living with the Physical Environment (Section A - The Challenge of Natural Hazards)
What is an earthquake?
An earthquake is a sudden and violent period of ground shaking, which is most commonly caused by sudden movements of rocks within the Earth’s crust.
Why is there a pattern of earthquakes?
They all occur at plate margins
Why do some earthquakes not occur at plate margins?
They are caused by human activity such as underground mining, reservoir construction or oil extraction.
How thick are tectonic plates?
100 km thick
What are the two types of crust?
- Oceanic crust: dense, thin
- Continental crust: less dense, thick
How do constructive plates move?
The plates move past each other. The build up of friction causes a sudden release which causes an earthquake.
Are there any tectonic hazards at a constructive plate margin?
- No land is created or destroyed
- As magma breaks through the surface, it triggers mild earthquakes
- There are shield volcanoes, as lava erupts and flows a long way before cooling
How do destructive (subduction) plates move?
The plates move towards each other, and the oceanic crust ends up subducting beneath the continental crust, as it is denser.
Why do plates move in relation to one another?
Due to the convection currents deep within the Earth
What is an example of a constructive plate margin?
‘Eyjafjallajokul’ in Iceland
How do destructive (collision) plates move?
The plates move towards each other, and neither are more dense, so they collide with each other.
Are there any tectonic hazards at a destructive (subduction) plate margin?
- The sudden vertical displacement over such large areas, disturb the ocean’s surface, and generate destructive tsunami waves
- There are composite volcanoes, as magma breaks through the surface to form steep-sided volcanoes, where eruptions are violent and explosive
What is an example of a destructive (collision) plate margin?
Himalayas - Indian and Eurasian plates collision
What is an example of a destructive (subduction) plate margin?
West Coast of South America
Are there any tectonic hazards at a conservative plate margin?
- Volcanoes do not form as there is no magma
- Earthquakes happen along this plate margin, as stresses gradually build up over many years. They can be destructive as they are close to the Earth’s surface. These are released when suddenly the plates slip and shift.
Are there any tectonic hazards at a destructive (collision) plate margin?
- As the plates collide, they are forced upwards, and they form fold mountains
- There are very destructive earthquakes, which are caused by plates sticking, so pressure builds up, and there is a sudden release as the plates slip. The secondary effects of an earthquake, can include fires, tsunamis, and aftershocks
- There are no volcanic eruptions here as there is no magma.
How do conservative plates move?
The plate move away from each other
What is an example of a conservative plate margin?
San Andreas Fault in California
What is a volcano?
A large, and often conical-shaped landform usually formed over a long period of time, by a series of eruptions
Where do volcanoes happen?
Like earthquakes, the majority of volcanoes occur in long belts that follow the plate margins, for example around the edge of the Pacific Ocean. This is known as the ‘Pacific Ring of Fire’. There is also a belt of volcanoes through the middle of the Atlantic Ocean. This is the Mid-Atlantic Ridge which includes the Azores and Iceland which are volcanic islands.
Why is there a pattern of volcanoes?
Volcanoes are fed by hot molten rock (magma) from deep within the Earth. This rises to the surface at constructive and destructive plate margins. Volcanoes also form at hotspots, where the crust is thin and magma is able to break through to the surface. The Hawaiian Islands in the Pacific Ocean are a good example of volcanoes forming at a hotspot.
What are some important facts about the Chile earthquake?
- 27 February 2010
- Destructive Subduction - Nazca Plate is moving beneath the South American Plate
- 8.8 magnitude
- Epicentre location: Sea
- 3 minutes long
- Followed by small aftershocks
- Tsunami warnings
- Waves rushed across the Pacific Ocean at 800km/hr
What are some important facts about the Nepal earthquake?
- 5 April 2015
- Destructive Collision, caused by Himalayas formation - Indo-Australian plate colliding with Eurasian plate, at a rate of 45mm/year
- Epicentre Location: Urban towns and villages (80 km northwest of Nepal’s capital Kathmandu)
- Very shallow earthquake - 15 km below Earth’s surface
- Severe ground shaking
- Wide spread landslides
- 7.9 magnitude
- Damage to hundreds of km away, in Pakistan, Tibet and India
- Avalanches
What are the (social) primary effects of the Chile earthquake 2010?
- 500 people killed
- 12,000 people injured
- 500,000 people affected
What are the (economic) primary effects of the Chile earthquake 2010?
- Cost of earthquake estimated at US $30 billion
- 220,000 homes, 4,500 schools, 53 ports, 56 hospitals and other public buildings affected
- Port of Talcahuano and Santiago airport badly damaged
What are the (environmental) primary effects of the Chile earthquake 2010?
Much of Chile lost power, water supplies and communications
What are the (social) primary effects of the Nepal earthquake 2015?
- 9,000 people killed
- 20,000 people injured
- Over 8 million people (a third of Nepal’s population) affected
- 3 million people left homeless when houses were destroyed
- 1.4 million people needed food, water and shelter in the days and weeks after the earthquake
What are the (economic) primary effects of the Nepal earthquake 2015?
- Cost of earthquake estimated over US $5 billion
- 7,000 schools destroyed and hospitals overwhelmed
- International airport became congested, as aid arrived
- 50% of shops destroyed, affecting food supplies and people’s livelihoods
What are the (environmental) primary effects of the Nepal earthquake 2015?
Electricity, water supplies, sanitations and communications affected
