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.
Magmas form by the melting of pre-existing (parent) silicate rocks. Three major mechanisms can cause a rock to melt... these are: 1  Heating-despite being an obvious cause, this is not usually the most important cause of magmas. 2  Pressure decrease-this is a very important mechanism at divergent boundaries.agmas form by the melting of pre-existing (parent) silicate rocks. Three major mechanisms can cause a rock to melt... these are: 1  Heating-despite being an obvious cause, this is not usually the most important cause of magmas. 2  Pressure decrease-this is a very important mechanism at divergent boundaries.