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Why are the Blue Mountains blue?

 

 

The Greater Blue Mountains Area of New South Wales is a sandstone plateau that holds a high diversity of eucalypts, representing all four existing groups. It is an area of rugged tablelands, sheer cliffs, deep, inaccessible valleys and swamps that contain ancient, relict species of global significance. The most famous of these is the recently discovered Wollemi pine, a 'living fossil' dating back to the age of the dinosaurs.

The site includes 8 protected areas:
- Blue Mountains National Park
- Wollemi National Park
- Yengo National Park
- Nattai National Park
- Kanangra-Boyd National Park
- Gardens of Stone National Park
- Thirlmere Lakes National Park
- Jenolan Caves Karst Conservation Reserve

The Blue Mountains, given that name due to the blue haze that hovers above them, is an area renowned for spectacular scenery, plant and wildlife and densely populated forests of oil bearing Eucalyptus trees. Thus, it is commonly believed that the blue haze blanketing the mountains is created by the atmosphere whereby dispersed droplets of Eucalypt oil combine with dust particles and water vapour to scatter refracted rays of light which are largely blue in colour.

However, because this is a common phenomena shared by mountain ranges elsewhere in the world, another theory suggests that:

the sky is blue because tiny air molecules of oxygen and nitrogen, water molecules, and dust motes interact with light. The small size of these particles means that high-frequency light (like, blue) is much more likely to interact than low-frequency light (such as red). The interaction scatters blue light in all directions. Consequently, we are more likely to see blue light than any other colour. Thus, the sky looks blue.

Consequently, distant dark mountains reflect little light to our eyes. Our eyes receive much more light from sunlight scattered by tiny molecules between us and the mountain. That scattered sunlight is blue. So, it isn't a scattering of light reflected from the mountain that makes the mountain appear blue, but rather a scattering of light between us and the mountain. (WeatherQuesting Web Site)

Blue Mountains Association of Cultural Heritage Organisations
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