Tectonic Hazards Flashcards
What are tectonic plates?
Huge floating plates that make up the Earth’s surface and are constantly moving.
Tectonic plates float on the mantle, which is a layer of semi-molten rock.
What are the two types of crust that make up tectonic plates?
- Continental crust (thicker, less dense)
- Oceanic crust (thinner, more dense)
Continental crust is 30-50 km thick, while oceanic crust is 5-10 km thick.
What causes tectonic plates to move?
Convection currents in the mantle.
These currents are caused by the heat from the Earth’s core.
What are plate margins?
The places where tectonic plates meet.
Also known as plate boundaries.
What are the three types of plate margins?
- Destructive margins
- Constructive margins
- Conservative margins
Each type has distinct movements and geological features.
What happens at destructive margins?
Two plates move towards each other; oceanic plate is subducted, creating magma, volcanoes, and ocean trenches.
Example: Nazca plate subducting beneath the South American plate forming the Atacama Trench.
What occurs when two continental plates meet?
The ground is folded upwards, creating fold mountains.
This process can lead to the formation of mountain ranges.
What occurs at constructive margins?
Two plates move away from each other, allowing magma to rise and create new crust.
Example: Mid-Atlantic Ridge formed by the Eurasian and North American plates.
What characterizes conservative margins?
Two plates move sideways past each other or in the same direction at different speeds; crust isn’t created or destroyed.
Example: San Andreas Fault.
Where do volcanoes commonly occur?
At destructive and constructive plate margins.
Volcanoes can also form at hotspots, such as in Hawaii.
How do volcanoes form at destructive margins?
The denser oceanic plate is subducted, melts in the mantle, and rises through vents to form a volcano.
The magma is referred to as lava once it reaches the surface.
What are pyroclastic flows?
Super-heated currents of gas, ash, and rock emitted during a volcanic eruption.
These flows can be extremely dangerous and destructive.
What causes earthquakes?
Tension builds up at all three types of plate margin due to plate movement.
Earthquakes can occur at destructive, constructive, and conservative margins.
What is the focus of an earthquake?
The point in the Earth where the earthquake starts.
Shock waves spread out from this point.
What is the epicentre of an earthquake?
The point on the Earth’s surface directly above the focus.
This location often experiences the most intense shaking.
How is the magnitude of an earthquake measured?
Using the moment magnitude scale, which measures the energy released.
It is a logarithmic scale, meaning each whole number increase represents ten times more ground shaking.
What magnitude of earthquake typically causes major damage?
Magnitude 7 and above.
Earthquakes of magnitude 6 and below usually cause only slight damage.
Why do many people live in areas affected by tectonic hazards?
Many people live close to volcanoes or in earthquake-prone areas due to factors such as economic constraints, lack of awareness, or personal choice.
What is a reason people may choose to live near Mount Etna?
They may have always lived there, leading to a reluctance to leave jobs or families.
How can effective monitoring and evacuation plans minimize risk in wealthier countries?
These strategies can enhance preparedness and response during tectonic events, reducing casualties.
What support did the Italian government provide during the 2001 Mount Etna eruption?
Financial aid and tax breaks for local residents.
Why is volcanic soil beneficial for farmers?
It is very fertile due to the minerals from volcanic ash.
What type of crops are ideally produced in the mineral-rich soil around Mount Etna?
Grapes.
How do volcanoes contribute to local economies?
They act as tourist attractions, providing jobs in the tourist industry.
What can management strategies do regarding tectonic hazards?
Reduce the number of people killed, injured, made homeless, or left unemployed.
What signs can scientists monitor before a volcanic eruption?
Tiny earthquakes, escaping gas, and changes in the shape of a volcano.
Can earthquakes be reliably predicted?
No, but their likely locations can be forecasted by monitoring tectonic plate movement.
What methods can be used for planning against tectonic hazards?
Avoiding high-risk areas for future developments and preparing emergency services.
How can new buildings be designed to withstand earthquakes?
Using reinforced concrete that absorbs earthquake energy.
What structural improvements can be made to existing buildings to protect against earthquakes?
Strengthening with steel frames.
What measures can be taken to prevent fires during an earthquake?
Automatic shut-off switches for gas and electricity supplies.
What strategies can be employed to mitigate the impact of volcanic eruptions on buildings?
Strengthening buildings to withstand ash weight and using trenches and barriers to divert lava.
What can be done to educate people about tectonic hazards?
Teach them what to do in the event of a hazard.
What should governments plan in advance of tectonic hazards?
Evacuation routes for safe and quick departures.
What types of emergency supplies should be stockpiled?
Blankets, clean water, and food.
