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.
If the magma reaches the surface it is called lava and lava accumulates to make a volcano.   Volcanoes grow by intrusion and extrusion. An intrusion is magma that moves up into a volcano and then it stops, never erupting.This way the volcano grows on the inside. An extrusion is an eruption.It can add layers of lava or ash. This way the volcano grows on the outside.   Volcanoes erupt because of density and pressure. The lower density of the magma causes it to rise (like air bubbles in syrup).rash, greenhouse gases, almost anything. Unfortunately, humans cause pollution from cars and factories and etc..... exhaust, smoke, litter and cutting down trees. throw â¦ ing household garbage, using old vehicles, smoking, using pesticides and insecticide Pollution is of various kinds, air, water, noise, etc.