Tectonic Hazards Flashcards
Describe the core of the earth:
Extremely hot and under a lot of pressure.
What is mantle?
A solid materials that flows very slowly and surrounds the core.
What is the asthenosphere?
The upper portion of the mantle which is a weak layer and can deform like plastic.
What is the lithosphere?
The crust and upper mantle form a rigid shell at the surface of the Earth.
How can movement of plates be tracked?
Using GPS.
What is a plate margin?
Where 2 plates meet.
What are 2 reasons why tectonic plates move?
-Convection
-Ridge push and slab pull
What is convection?
The core’s temperature is around 6,000C. This causes magma to to rise in the mantle and sink towards to the core when it cools.
What is ridge push?
At constructive margins, ocean ridges form high above the ocean floor. Beneath ocean ridges the mantle melts; the molten magma rises as the plates move apart and cools down to form new plate material. As the lithosphere cools, it becomes denser and starts to slide down, away from the ridge, which causes plates to move away from each other.
What is slab pull?
At destructive margins, the denser plate sinks back into the mantle under the influence of gravity, which pulls the rest of the plate behind it.
What are the 3 types of plate margins?
Constructive, destructive and conservative.
What is convection?
The core’s temperature is around 6,000C. This causes magma (molten rock) to rise in the mantle and sink towards the core when it cools. The currents flow beneath the lithosphere, building up lateral pressure and carrying the plates with them.
Where are earthquakes found?
At all 3 plate margins.
Where are volcanoes found?
On constructive and destructive plate margins.
What is the Ring of Fire?
A large band of volcanoes and earthquakes which circles the pacific ocean.
What are ‘hot spots’?
Sometimes earthquakes and volcanoes occur in the middle of plates, where the Earth’s crust is thought to be particularly thin.
Give an example of a hot spot:
Hawaii has formed due to volcanic eruptions at a hot spot that is located far from the edge of the Pacific plate.
How do earthquakes form at constructive plate margins?
When the risen molten magma cools it forms solid rock, this can sometimes fracture as it is moved, causing earthquakes.
How do volcanoes form at constructive plate margins?
The upper part of the mantle melts and hot molten magma rises. As the plates move away from each other, the molten magma rises in between and cools to form solid rock. In a few places, the magma erupts on to the surface, producing a lava that is runny and spreads out before solidifying. Over many eruptions a volcano with a typically wide base and gentle slopes, known as a shield volcano, is formed.
What are rift valleys?
On land, constructive plate margins form a steep-sided valley known as a rift valley, where the land drops as plates move apart.
Give an example of a rift-valley?
The Mid-Atlantic Ridge.
Which plate is denser?
The oceanic plate.
Which plate is subducted at a destructive margin?
The denser oceanic plate.
Name 3 things that occur at destructive plate margins:
-Earthquakes
-Fold mountains
-Volcanoes
Why do earthquakes happen at destructive plate margins?
As the plates converge, pressure builds up. The rock eventually fractures, causing an earthquake, which can be very destructive.
Give 5 economic reasons for living at risk from tectonic hazards?
-Geothermal energy
-Farming the nutrient-rich soils helps agriculture
-Mining provides energy and income
-Tourism creates jobs and provides income
-It may be cheaper to stay than move
Give 3 social reasons for living at risk from tectonic hazards?
-People want to stay near friends and family
-The threat may not be great enough, or people don’t understand risk
-People are confident that the buildings will keep them safe
What are 4 ways to monitor a volcanic eruption?
-Changes in shape of ground and volcano using tiltmeters and GPS satellites
-Earthquakes near magma chambers using seismometers
-Ground surface and river temperatures using thermal heat sensors
-Radon and sulphur gas using gas-trapping bottles
Which is easier to predict, volcanoes or earthquakes?
Volcanoes, as they usually as they usually give advance warning signals before erupting.
What are 2 ways to protect against a volcanic eruption?
-Buildings can not be designed to completely protect against eruption impacts
-Evacuation instructed by authorities
What are 4 ways to plan for a volcanic eruption?
-Evacuation
-Exclusion zones
-Education to know what to do
-First-aid training
Which is harder to monitor, volcanic eruptions or earthquakes?
Earthquakes.
What are 2 ways to monitor an earthquake?
-Foreshocks using seismometers and GPS
-Radon using radon detection devices
What are 2 ways to protect against an earthquake?
-Building and transport infrastructure (eg foundations with rubber shock bearings) though these are expensive
-Sea walls in case of tsunamis
What are 3 ways to plan for an earthquake?
-Practise drills
-Preparing emergency supplies and location of evacuation centres
-Securing objects/furniture
