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.
About. Magma is liquid rock in between the crust and the mantle, formed when part of the lower crust or upper mantle melts. When magma travels up through a volcanoâs vent, bubbles of gas also appear. All the gas builds up pressure, which causes the magma to explode out of the volcano. Many volcanoes are mountains, made up of layers of lava and ash. 2  Many volcanoes have several vents â a main one, and secondary ones that branch off the main vent. 3  The volcanoâs main vent goes all the way down to the layer of magma in between the Earthâs crust and mantle.