One of the key reasons for Federation was to achieve a united defence force which could better protect Australia. Around the 1880s, the Australian colonies had become increasingly concerned over the close proximity of foreign powers.
Split and merge into it. Answered by The Community. Making the world better, one answer at a time. Dissolved gases trapped in the magma provides the force that causes magma to erupt to the surface. Magma is molten material before it reaches the surface and is lava.
A2) Explain how subduction leads to volcanic activity. One of the plates will be pushed down by great pressure and temperatures so deep that the water from the subducting slab will begin to accumulate between both plates then eventually the plate will melt once the water lowers the temperature of the mantle. The magma then rises to the surface to produce a linear belt of volcanoes.