Australia: The Land Where Time Began

A biography of the Australian continent 

Basalt (Oceanic Crust)

A dark coloured, fine-grained, crystalline rock, generally composed of minerals such as olivine, quartz and  hypersthene, though often also with apatite and magnetite. Can be formed by volcanic eruption (extrusive formation) or underground (intrusive formation). Crystal size is small because of rapid cooling. It forms the main part of oceanic crust between the continents. It is denser than granite and so moves below continental margins at subduction zones.  It is often spread over the granite continents by volcanic eruption as found in parts of Western Australia.