Restless Earth Flashcards
What are the layers in the Earth?
Core, mantle, crust
What are the four types of plate boundaries?
- Constructive
- Destructive
- Collision
- Conservative
What happens at constructive plate margins? (4)
- Plates move apart
- Both oceanic crust, mainly happens above oceans
- Magma rises up and forms new land
- An example is Iceland on the mid-atlantic ridge
What happens at destructive plate margins? (6)
- When plates move together
- 1 oceanic and 1 continental, oceanic crust subducts beneath the continental crust
- An oceanic trench is formed at the subduction zone
- Oceanic crust is destroyed and melts to form magma
- The magma rises and forms composite volcanoes
- Earthquakes
What happens at collision plate margins? (4)
- When plates move together
- 2 continental crusts
- The plates are pushed upwards forming fold mountains
- An example is the Himalayas
What happens at conservative plate margins? (6)
- When plates slide past each other
- They move at different directions and speeds so they tend to get stuck
- Friction, pressure, jerking of plates, earthquake!
- Shallow earthquakes
- No volcanoes
- An example is the San Andreas fault
How are fold mountains formed?
How are ocean trenches formed?
They’re deep sections of the ocean formed at destructive plate boundaries where the oceanic plate is subducted beneath the continental plate
What are the different types of volcano?
Shield and composite
Describe shield volcanoes (4)
- Form at constructive plate margins
- Wide base and gentle slope
- Basic lava (runny and flows quickly)
- Regular eruptions with little violence
- Examples: Surtsey in Iceland, Mauna Loa in Hawaii
Describe composite volcanoes (6)
- Form at destructive plate margins
- At the subduction zone, the plate melts and forms a magma pool. The magma is forced to the surface under great pressure where it erupts
- Alternating layers of lava and ash
- Tall cone with narrow base and steep sides
- Irregular eruptions with long dormant periods
- Violent explosions
What are the benefits of volcanoes? (4)
- Volcanic soils are fertile so they’re very good for farming. Near Vesuvias the yield is 5 times better than the national average in Italy
- Tourist attractions, bathing in hot springs/mud pools, geysers, trips to the crater. Local people can make money
- Hot water can be used as heating or generating electricity
- Valuable minerals
How can volcanic eruptions be predicted? (3)
- Small earthquakes
- Increased steam and gas emissions
- Robots can be used to measure the gases released
- Visual bulging around the crater
- Tiltmeters and satellites measure movement
How can the impacts of volcanic eruptions be reduced? (3)
- Land use zoning and hazard mapping
- Lava can be sprayed with water
- Large concrete blocks can divert the lava flow
What is a supervolcano?
A mega colossal volcano that erupts at least 1000km3 of material. They occur at hot spots.
What are the characteristics of a supervolcano?
Large depressions called calderas
Where do earthquakes occur?
- Destructive plate margins
- Conservative plate margins
- Constructive plate margins
What is the focus of an earthquake?
The point in the earth’s crust where the earthquake originates
What is the epicentre of an earthquake?
The point on the Earth’s surface directly above the focus
What are the shock waves of an earthquake?
Seismic waves that travel through the Earth’s crust
How can earthquakes be measured?
- The Richter Scale
- The Mercalli Scale
Describe the Richter Scale
- Based on scientific recordings]
- Logarithmic, 10-fold increase each time the scale increases by 1
- A number between 1 and 10
Describe the Mercalli Scale
- Based on the visible effects of the surface, people and buildings
- Roman numerals
- I to XII
What are the 3 P’s?
- Prediction
- Protection
- Preparation
