Year 9 - Topic 1 - Tectonics Flashcards
What four layers is the Earth divided into?
Crust
Mantle
Outer Core
Inner Core
What do tectonic plates do?
Tectonic plates are ‘floating’ on the semi-molten layer of rock in the mantle
What is the crust of the Earth divided into?
Tectonic plates
What are the two types of crust?
Continental crust
Oceanic crust
What is continental crust?
Forms the land, is low density (light) and is 30-50km thick
What is oceanic crust?
Forms under the sea, dense (heavy) and is 6-8km thick.
Explain convection currents
Heat from the core causes convection currents in the mantle where the heated rock rises towards the crust.
This causes the tectonic plates (crust) to move constantly - either towards or away from one another.
What is a plate boundary?
A plate boundary is the point at which two tectonic plates meet
What are the three plate boundaries?
Constructive plate boundary
Destructive plate boundary
Conservative plate boundary
What is a constructive plate boundary?
Two tectonic plates are moving apart from one another. The gap in the crust causes magma to rise and cool. Earthquakes and volcanoes occur here.
What is a destructive plate boundary?
When two plates move towards each other one sinks (subducts) below the other one. Volcanoes and earthquakes occur here.
What is a conservative plate boundary?
When two plates are moving side by side, in different directions or the same direction but at different speeds. Earthquakes occur here.
What is an earthquake?
An earthquake is the shaking and vibration of the Earth’s crust. It happens when the Earth’s tectonic plates move. They can happen along any of the plate boundaries.
What is a volcano?
A volcano is an opening in the Earth’s surface through which lava and ash escape. Volcanoes can be found at destructive or constructive plate boundaries.
What are the two types of volcanoes?
Shield Volcano
Composite Volcano
Describe shield volcanoes
Wide base
Gently sloping sides
Runny lava
Eruptions are frequent and produce ash
Describe composite volcanoes
Cone shaped
Steep sided
Sticky lava
Eruptions are violent but not frequent
What is a tsunami?
A tsunami is a large wave caused by the displacement of a large amount of water when an earthquake occurs under the sea. This creates a wave that increases in height as it approaches the shore.
What are social effects of tsunamis?
High death rate
People become homeless because homes and buildings are destroyed
Threat of disease
What are economic effects of tsunamis?
Ports are ruined
Businesses are destroyed (e.g. the destruction of ships can affect fishing businesses)
Loss of earnings from tourism
What are environmental effects of tsunamis?
Crops are destroyed
Farmland ruined by saltwater
Large oil spills can occur
What were short-term responses from the Indian Ocean Tsunami (2009)?
Quick burial or burning of the dead to prevent spread of disease
$7 billion of foreign aid
What were the long-term responses from the Indian Ocean Tsunami (2009)?
Indian Ocean Tsunami warning system set up
Charities set up small scale projects to help local people rebuild lives
What are general effects of volcanoes?
Lava can kill and destroy farmland
Heavy pyroclastic flow can cause buildings to collapse
Gas, dust, ash and cinder bombs can fly out of the volcano causing injury and death
Dust from volcano can cause planes to crash
Toxic gases can cause health problems e.g. breathing problems and eye damage
