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One type of plate boundary is known as the constructive plate boundary. This consists of two plates moving away from each other which leaves a gap in the middle, this gap allows magma to seep through. As it rises to the top, it cools due to water and makes basalt which volcanoes are made out of. Finally this basalt creates a new crust/ocean floor.
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A second type of boundary is a collision plate boundary, this is when two plates with around the same density bash into each other and rise upwards. Due to the rising it lifts the land into hills or, 'fold mountains'. They then separate due to the magma rising from the gap in the middle of the two plates, which pushes them outwards as the lava rises. Despite magma being being involved it causes neither earthquakes or volcanoes.
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Yet another type of plate boundary is called a destructive plate boundary. A destructive plate boundary occurs when two plates of different densities collide (e.g. oceanic and continental plates). The plate that is made of denser rock shall be dragged underneath the other because the pressure is so great. The denser plate starts to melt because of the friction and turns in to magma. If this magma reaches the surfaces it can cause volcanoes.
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Finally, the last type of plate boundary is called a conservative plate boundary. This happens when two plates of similar density meet at diagonals and are going opposite to each other side ways. This movement creates a lot of friction, so this type of plate boundary can cause many earthquakes.