Tectonic Hazards Flashcards
Define natural event
A naturally occurring phenomena, has no threat on people and infrastructure
Define natural hazard
A naturally occurring event which imposes threat on people and infrastructure
Define natural disaster
A natural hazard which kills over 10 people and causes economic damage
Give 2 examples of tectonic hazards
Volcanoes- eyjafjallajokul
Earthquakes- ghorka
Give an example from the risk equation
High population density- if an earthquakes epicentre is in a city where the population is dense, there is increased chance of death and damage to property.
Older population- will take longer to evacuate, increased chance of death
Wealth- LIC’s usually have fewer resources and poorer infrastructure, higher chance of damage to property and death
Give two examples of continental drift
Puzzle fit of South America and Africa
Fossils of similar shapes found on different continents
Define continental drift
The movement of the Earth’s continents over time
What makes up the lithosphere
The crust and upper mantle
Convection currents
The earth’s core is very hot- magma is heated and it evaporates, so it rises and cools and condenses, it sinks and becomes denser, creating a convection current. This creates a build up of pressure
Ridge push
When two plates move away from each other, magma rises and cools to form new crust. As it cools it becomes more dense and slides away from the ridge, causing the plates to move away from each other
Slab pull
The oceanic plate is subducted under the continental plate as it is denser, it moves towards the mantle due to the force of gravity, dragging the rest of the plate along with it
Destructive plate margins
Plates move towards each other due to convection currents in the mantle, slab pull forces the oceanic plate underneath the continental plate due to gravity. The plate melts and forms magma which is released and forms a volcano. The build up of pressure is released as seismic waves (earthquake).
Causes composite volcanoes and big earthquakes
Forms ocean trenches and fold mountains
Constructive plate margin
Plates move away from each other due to convection currents in the mantle, ridge push causes magma to rise and form new crust
Forms shield volcanoes and small earthquakes
Forms rift valleys
Conservative plate margin
Two plates sliding past each other, a build up of pressure is created due to friction. This causes the rock to fracture, causing earthquakes
No volcanoes
Forms fault lines
Collision plate margin
Two continental plates moving towards each other, neither are subducted so they form fold mountains,
No volcanoes
Causes earthquakes
Give an example of a destructive plate boundary
Eurasian plate (continental) and Indo-Australian plate
South American plate and nazca plate
Give an example of a conservative plate margin
The San Andreas fault line
North American plate and pacific plate
Give an example of a constructive plate margin
North American plate and Eurasian plate
Give an example of a collision plate margin
India plate and Eurasian plate
Differences between oceanic and continental crust
Oceanic:
-denser
-newer
-thinner
-can be destroyed
Continental:
-less dense
-older
-thicker
-cant be destroyed
Give an example of fold mountains
The Himalayas
Give an example of an oceanic ridge
Mid-Atlantic ridge
Describe the global distribution of volcanoes
Found on only constructive and destructive plate boundaries
Describe the global distribution of earthquakes
Found at every plate boundary
