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Continental drift

The theory that the continents were once one large landmass but they have drifted apart over time

What evidence is there that the continents where once all together ?

1. Fossils


There are same species fossils found in both Africa and South America



2. Mountain ranges


Old mountain ranges lined up and mountains were formed of the same type, age and structure



3. Ocean floor spreading


The Atlantic Ocean didn't exist when the continents where together. Once the continents started drifting apart the Atlantic Ocean appeared and is getting larger since: ocean floor spreading.


Geologists have found rocks of the same age and type of either side of the mid Atlantic

What are tectonic plates?

A section of the earths crust which can move on the mantle

Explain the mechanics of plate boundaries :

Heat inside the earth provides the energy for mechanics which causes the plates to move.



Heat rises from the core and spreads through the mantle in convection currents



These currents form convection cells so heat is constantly moving towards the crust



At the top of each convection cells the convection currents moved sideways and eventually downwards to complete the cells


Plate boundaries

The edge of a tectonic plate

Conversant plate boundaries

A plate boundary where played are moving towards each other

Divergent plate boundary

A plate boundary where played are moving apart

Passive or transverse plate boundary

A plate boundary where played slide past each other

What are the landforms associated with different plate boundaries?

Folded mountain ranges:


Form along convergent plate boundaries involving two continental plates or a continental plate and an oceanic plate



When these yo plates collide this folds up and lifts layers of sedimentary rocks that had been laid down between them . This forms mountains called fold mountains



Ocean floor spreading


Mid Atlantic ridges occur along divergent plate bondaries involving two oceanic plates. The two plates pull apart and as magma rises up and solidifies at the surface, new land is created between the plates.



Oceanic trenches:


Occur along conversant plate boundaries where an oceanic plate converges with a continental plate. Oceanic plate consists of denser rocks so it slides under neater the continental plate. This causes the seabed to form a deep trench all along the subduction zone

Constructive plate boundary

A plate boundary where new land is forming

Subduction zone

A deep trench on the ocean floor where an oceanic plate is drawn under along a plate boundary

Destructive plate boundary

A plate boundary where land is being destroyed