Restless Earth Flashcards
What are the four layers of the earth?
Inner core, outer core, mantle and crust
How thick is the crust?
10-25miles
What is the crust made up of?
Soil, water and rock
What are features of oceanic crust?
Can subduct Can be renewed and destroyed Newer-200million years old at most Denser Made of silicone and magnesium (sima)
What are features of continental crust?
Cannot sink Connot be renewed or destroyed Older, mostly over 1500million years old Less dense Made of silicone and aliminium (sial)
How thick is the mantle?
1800 miles
What is the temperature of the mantle?
500-2000°c
What are the two layers of the mantle?
Lithosphere and Asthenosphere
What is the mantle made of?
Partly melted and partly solid iron and magnesium
What is the outer core made of?
Liquid nickel and iron
How hot is the outercore?
5000°c
How thick is the outercore?
1430miles
What is the radius of the inner core?
750 miles
What is the inner core made of?
Solid nickel and iron
What causes plates to move? And what causes these?
Convection currents in the mantle which is caused by nuclear decay in the core. Hot material rises and cools at the top which drags the plates
What are the three types of plate margin?
Constructive, destructive, conservative
What occurs at constructive plate boundaries?
The plates moving away which allows magma to rise SHEILD VOLCANOES
Where are most constructive plate boundaries?
Usually under the sea
What is an example of a constructive plate boundary?
Mid atlantic ridge in Iceland
What happens at a destructive plate boundary?
2 plates move towards eachother, lighter continental crust stays on the top whilst the oceanic crust subducts into the mantle where it melts
What sort of volcanoes are featured at a destructive boundary?
Composite
What four things are features of a destructive plate boundary?
Composite volcanoes
Violent earthquakes
Ocean trenches
Fold mountains
Which plate margin doesnt feature volcanoes?
Conservative
What is an example of a conservative plate margin?
The San Andreas fault line, north american plate and pacific plates
What are three examples of fold mountains?
The Himalayas
The Andes
The Alps
Explain the formation of fold mountains
Rivers carry sediment into a geosyncline The sediments build up Convection current drive plates together Sediments begin to up lift Fol mountains are formed with sinclines and anticlines
What is the anticline?
The uplcline of fold mountains/folded rocks
What is a sincline?
The down fold of folded rocks
What is an overfold?
Where a fold has been pushed over on one side
What case study is used for human uses of fold mountains?
The Alps
Where are the Alps?
750miles/1200km from the border of Italy
Bordering the countries of France, Austria and Slovenia
Which plates are pushing against eachother to form the Alps?
The African and Eurasian
What is the highest point of the Alps?
Mont Blanc 4810m
What generates HEP in the Alps?
Water run off from melting snow, high precipitation, melting glaciers. They produce fast flowing rivers
How much energy does the Grand Dixence provide Switzerland with?
70%
What is transhumance farming?
Letting cattle graze on the mountains in summer then returning them to sheds on the valley floor in winter
Why do people visit the Alps in summer?
For the lakes, beautiful scenery and hiking
What is a disadvantage about winter sports of the Alps?
The slopes are being worn down which is increasing the number of bare surfaces and the risk of soil erosion. This can damage local vegetation
What is a plentiful resource in the Alps?
Wood from coniferous trees
What is a dormant volcano? Add example
Hasn’t erupted in 2000 years e.g Santorini, Greece
What is an extinct volcano? Give and example
Unlikely to erupt ever again e.e. Devil’s Tower, Wyoming
What is an active volcano? Give an example
Has erupted recently and likely to erupt again e.g. Mt Etna, Sicily
Where are sheild volcanoes formed?
Constructive boundaries
How are sheild volcanoes formed?
Magama rises between the plates to fill the gap
Which type of volcano is more destructive/explosive?
Composite
Which volcano’s lava is more viscous?
Composite
Which volcano has gentle slopes with a wide base?
Sheild
What is a composite volcano made of?
Layers of lava and ash
What is an example of a sheild volcano?
Surtsey Island, Iceland
What is an example of a composite volcano?
Mt Etna, Sicily
Krakatoa, Indonesia
Why do humans live near volcanoes?
- The local soil is very fertile when mixed with volcanic ash
- The geothermal energy
- sulfur mining in Indonesia
- diamond, gold, silver, copper mining
- tourism like at Mt Fiji in Japan where over 100million tourists visit a year
What do people say for why they choose to live near a volcano?
‘The positives outweigh the negatives’
What is a supervolcano?
A colossal volcano that erupts atleast 1000km^3 of material
Where is the main distribution of supervolcanoes?
The west of the Nort American plate
What are some causes of a supervolcano?
Destructive plate margin where magma can rise and make a hotspot
The magma rise through a pipe from the mantle to the crust where it gets trapped underneath a layer of rock
As it increases in size, the pressure adds to the crust
Eventually the crust gives in and collapses to form a caldera
What escapes through cracks in a caldera?
Lava, tephra and pyroclastic flows
What are some features that are close to supervolcanoes?
Geysers
Fissures
Caldera
What is a fissure?
An extended opening that along the line of weakness which allows magma to escape
Where do earthquakes occur?
All three types of plate margin
What is the focus of an earthquake?
The point at which the earthquake happens beneath the earth
What is the epicentre?
The location of the focus on the surface of the crust
What is a seismic wave?
Waves that radiate out in all directions from the focus
Why do earthquakes occur?
When two plates move past eachother without a smooth movement
What causes the pllates to get stuck and what does this cause?
Friction then pressure
What are the two different scales to measure earthquakes?
Richter and Mercalli
What is the main difference between the richter and mercalli scale?
The Richter uses a mathematical grapher whereas the mercalli scale is based on opinion (subjective)
What does the richter scale go up to?
10
What does the mercalli scale up to?
12
What is the mercalli scale based on?
The impact of the earthquake
Who invented the Mercalli scale and when?
Guiseppe Mercalli, 1902
Who invented the Richter scale and when?
Charles Richter, 1935
Why is a tsunami seen as a secondary effect?
Because an earthquake has to trigger it first
How do tsunamis occur?
- Plates push together and get stuck
- this causes an earthquake from the upward movement of one plate
- this action displaces water above it in the sea
- waves build up whilst moving towards land
- eventually a huge wave drives towards land
