Changing colours of Ayers Rock in Australia
Ayers Rock is the largest sandstone monolith in the world and is situated in the desert of Australia's Northern Territory. This sandstone monolith undergoes a unique transformation during the day as its colour changes from bright orange at dawn to a dark red colour at dusk.
Ayers Rock is in reality an inselberg rather than one huge stone. An insleberg means "island mountain" which has been formed by wind-blown sands. It is the remnant of the sandstone mountains that rose from the surface 500 hundred million years ago.
The changing colours of this huge monolith is due to the different types of rocks, such as marble and granite, which Ayers Rock is composed of. When the Sun shines on these rocks, they change colour. For example, marble can change colour from white, to pink as well as a spectrum of colours to black.
The geometrical structure of rocks is also an important factor in determining their colour. The structure of a rock is responsible for how it absorbs or reflects wave-lengths of light. Any type of variation, no matter how small, affects the colour. The result is that rocks change colour depending on the quality and brightness of light during the day.
The most common mineral in rocks, including Ayers Rock, is iron which is a colourant. Iron based minerals such as haematite are a brownish-red colour according to the amount of oxygen mixed in with it. Limonite is another example of an iron based mineral which is a yellow-chestnut colour when a lot of oxygen is present. These two minerals give the landscape a complete range of different colours.
Iron based minerals without any oxygen being present give rocks a black or greenish tinge. Rocks with copper present in them are blue or green, manganese and colbalt colour rocks pink and mercury give rocks a red colour. Impurities in minerals are also responsible for colour variations. For example, orthoclase, which is a crystaline mineral found in granite, give rocks a reddish colour.
The surface of Ayers Rock is actually rough rather than smooth. There are caves and fissures as well as black creeks where water drains away after infrequent showers of rain.
The magnificent beauty of Ayers Rock is undeniable and its changing colours are truly one of natures' wonders.
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