Gcse- Plate Tectonics Flashcards
How are earthquakes and volcanoes caused?
Caused by eruptions caused by movement within the earth
What belts do earthquakes occur in?
Pacific Ocean
Mid-Atlantic ocean
Stretch across Southern Europe and Asian
What does the earth consist of?
Middle- core
Outer middle- mantle
Surface layer- crust
Outer- plays boundary
Where do earthquakes and volcanoes occur at?
They occur at narrow zones of activity
What is crust broken into?
Crust is broken into segments known as plates which can float on mantle.
What happens with heat within the earth?
Heat within the earth creates convection currents convection currents which cause plates to move.
Where do most earthquakes and volcanic eruptions occur?
Where plates meet at a plate boundary.
What do most plates consist of?
Continental crust and oceanic crust
Characteristics of oceanic crust-
Young
Heavy
Can sink and is constantly getting destroyed.
Characteristics of continental crust-
Old
Light
Cannot sink and is permanent
What do crust differences account for?
Crust differences account for variation in processes and landforms, and level of activity at plate boundaries.
Describe what happens at a constructive plate margin-
2 plates move away from eachother. Oceanic crust appears forming mid-oven ridge with volcano. Gentle volcanic and earthquake activity.
Describe what happens at a destructive plate margin-
Oceanic crust moves towards continental crust, but because it’s heavier, it sinks and get destroyed forming an island arc. Violent volcanic and earthquake activity.
Describe what happens at collision zones-
2 continental crusts collide, neither sinks so they are forced upwards to form fold mountains. Can be violent earthquake activity.
Describe what happens at conservative margins-
2 plates move sideways past eachother, land isn’t formed or destroyed. Can be violent earthquake activity.
What happens at constructive margin(more expansive)
2 plates move away from eachother, magma rises to fill gaps and form new oceanic crust. Process is called sea-floor spreading.
What occurs at destructive plate margins?(expand)
Plates consisting of oceanic crust move towards plates of continental crust. In the South Pacific Ocean, nazca plate is forced downwards to form subduction zone and deep sea trench. Increase in pressure as plate is forced downwards can trigger earthquakes. As oceanic crust descends, it melts due to heat from friction caused by contact with South America plate.
What occurs at collision margins? (Expand)
2 plates consisting of continental crust move together. Continental crust can’t be sunk or destroyed, rocks between are forced up to form fold mountains.
What happens at conservative margins? (Expand)
2 plates slide past eachother. As crust is neither formed or destroyed, new landforms are not created and there is no volcanic activity. Earthquakes occur when plates stick. This is situation in San Andreas fault. When pressure builds one plate jerks forward sending shockwaves to surface cause earthquake.
