Geography

Explain how an Ocean Ridge is formed

An Ocean Ridge is formed at a constructive plate boundary when the plates are being pulled away from each other (gravitonal sliding) by convection currents in the mantle. For example, the Mid-Atlantic Ridge(4,00km)  is formed by the North American and Eurasian plate diverge. This creates a fissure between the two plates. The magma heated by the core rises as it less dense to plug the gap and diverges at the crust, therefore dragging the plates apart. As it rises it solidifies to form a ridge. When the magma sinks back down again and cools it is reheated and the sequence begins again in a circular motion. We can see an example of this ridge in Surtsey in Iceland where the highest point of the ridge as reached the surface.  The ridge will eventually level out the further away you get to form part of the abysll plane.

Explain how fold mountains are formed

Fold mountains occur at collision plate margins where to continental plates meet. When two continental plates meet there is no subduction here due to similar densities. Instead the land is compressed and buckles upwards. The Himalayas are made out of sedimentary rock as millions of years…