Geology Hacked: Types of Crusts and Plate Movements

Geology: Types of Crusts and Plate Movements

Types of crust

Two main types of crust

·        Oceanic crust

o   Denser crust

o   Less silicon

o   More iron and magnesium

o   Thinner and darker in colour, projects below sea level

·        Continental curst

o   More aluminium and silicon

o   Above sea level

Types of Plate Movement

Diverging boundaries (constructive boundary)

·        Plates moving apart from each other in opposite directions

·        Mid-ocean ridges are formed

·        Rift is formed between plates -> magma rises up -> new crust

·        Can occur on land

o   Iceland- mid ocean ridge runs through it -> volcanic eruptions

·        Rift valley (Great Rift Valley) in East Africa. New ocean forming

Converging boundaries (destructive boundary)

·        Plates colliding with each other

·        Oceanic and continental crust colliding

o   Dense oceanic plate sinks under continental (subduction)

o   Fold mountain and volcanoes

o   Ocean Trench is formed

§  Nazca plate and South America (Andes Mountains)

o   Friction of the plates colliding and mantle generate heat.

o   This melts the crust.

·        Two continental plates colliding

o   Both pushed upwards because same density -> high mountains

o   Indian and Eurasian plate = Himalayas

·        Two oceanic plates colliding

o   Faster moving plate subducts

o   Volcanic islands (island arc) appear as magma formed by subducted plate rises.

o   Evidence to theory as subduction must be occurring where trenches exist.

§  Mariana Trench =deepest trench in the world.

Transform boundaries

·        Two plates sliding parallel to each other but in opposite directions

·        Earthquakes and fold mountains (also occur in oceans)

·        Fault lines- cracks in the rocks

o   Pacific plate and North American plate move past each other= San Andreas Fault

o   Australian and Pacific plate collide = mountains in New Zealand