|Figure 1. Newspaper excerpt from 1828 announcing an active volcano in Australia.|
Mount Wingen, 530 m above sea level, is the highest of two contiguous hills in the Upper Hunter Valley. It is located 25 km North of Scone via the New England Highway and approximately 4 hr drive from Sydney. Its official name is the Burning Mountain Nature Reserve, and I had the pleasure of visiting it in early February 2014 (Fig. 2). The visit fulfilled one of my most desired field trips. I was attending the 11th International Symposium on Fire Safety Science in New Zealand, and I could not forgive myself from a quick stop over to see the Burning Mountain.
|Figure 2. Entry to the Nature Reserve of The Burning Mountain, including my symposium bag.|
The nature's sport that Rev. Wilton was referring to is the smouldering combustion of a coal seam. The Burning Mountain is the best example of this natural phenomenon that slowly burns the underground coal when it becomes exposed to atmospheric air. Smouldering is the slow, low-temperature, flameless burning that represents the most persistent type of combustion phenomena and leads to the largest and longest burning fires on Earth. This Australian coal seam started to burn more than 6,000 years ago, some scientists think more than 500,000 years ago. At least the British cannot be blame for it.
The fire is burning now about 30 m below ground. At a rate of 1 m per year, the fire has now reached the top of the hill which shown in Figure 3. Because of the creeping spread rate, the slow intense heat has created a landscape clear of any vegetation 50 m around. The soil shows an beautiful colour palette of white sinter, yellow sulphate, black char and red iron oxide. Where the fire and heat has not reached yet, a healthy forest of mature and tall trees can be seen on brown soil. Along the former trail of the fire path, the forest grows back slowly, and young and smaller trees can be seen on red soil. Once at the hilltop, it is easy to feel the hot combustion gases and the smell of sulfur released from multiple deep cracks. The site is surrounded by cracks, some are up to 0.5 m wide, which are more visible ahead of the fire than behind it. Further from the active site by about 20 m, the cracks do not emit gases which to me indicates that the airflow direction is into the seam, feeding the fire with vital oxygen.
|Figure 3. The fire has now reached the top of the second hill, where the soil is also a multicolor palette of white sinter, yellow sulphate, black char and red iron oxide.|
|Fig 4. Google maps of the reserve showing the approximate track and the current location of the fire at the top of the second hill.|
The Burning Mountain is just one example. Thousands of underground coalmine fires have been identified around the world, especially in China, India and USA. Elusive, unpredictable and costly, coal fires burn indefinitely while there is fuel, choking the life out of a community and the environment while consuming a valuable energy resource. The associated financial costs run into millions of dollars including the loss of coal, closure of coal mines, damage to the environment and fire-fighting efforts. There are other well-documented cases like when in 1962 an abandoned mine pit in Centralia, Pennsylvania, USA was accidentally lit. Many unsuccessful attempts were made to extinguish it, letting the fire continue to burn until today after more than forty years. Geologist estimate that there is fuel for 250 years more of fire.
Recommended reading (and viewing) on smoldering fires:
- Abbott, W.E., 1918. Mt. Wingen and the Wingen Coal Measures. Angus & Robertson, Sydney. http://trove.nla.gov.au/work/21299713
- Mayer, W. , 2009, Geological observations by the Reverend Charles P. N. Wilton (1795 -1859) in New South Wales and his views on the relationship between religion and science, Geological Society, London, Special Publications 310, p197-209. http://dx.doi.og/10.1144/SP310.20
- Smouldering, Wikipedia, http://en.wikipedia.org/wiki/Smouldering
- Smouldering Fires and Natural Fuels, by Guillermo Rein, Chapter 2 in:
Fire Phenomena in the Earth System – An Interdisciplinary Approach to Fire Science, pp. 15–34, Wiley and Sons, 2013. http://dx.doi.org/10.1002/9781118529539.ch2
Stracher, G.B., Prakash, A. & Sokol, E.V. (eds) (2010) Coal and Peat Fires: A Global Perspective, 1st edn; vol. 1: Coal – Geology and Combustion. Elsevier Science.
- Pennsylvania's 50-Year-Old Coal Fire by SciShow. www.youtube.com