Burning Mountain is the common name given for Mount Wingen, a hill near the small town of Wingen, which is about 225 km north of Sydney, on the New England Highway.
The Burning Mountain Nature Reserve is managed by the National Parks and Wildlife Service (of NSW), who have put a track and elevated walkway into where the vegetation has been scorched; with several information signs.
It has been estimated that currently the fire is 30 m underground, and moving in a 'southerly' direction, at about a metre per year. With estimations of this having been started some 5,500 years ago, this could be the oldest underground fire in the world, and certainly in the Southern hemisphere.
From: (
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"Underground coal fires are quite common throughout the world, often in coal mines. Coal seams can be ignited by lightning or wildfires and the seam can continue to burn indefinitely, even after the surface fire has been extinguished. The fires are extremely difficult to extinguish and often are the source of new bush fires."
Geology:
"The nature reserve surrounding Burning Mountain comprises two small blocks joined by a narrow strip of land. The reserve is located on a prominent ridge and the two blocks occupy part of the north- western slope of Mount Wingen and the north-eastern slope of Burning Mountain. The northern block consists almost entirely of the Koogah Formation (sandstone, shale, conglomerate and coal), with a minor occurrence of Bickham Formation rocks (lithic sandstone, conglomerate). The southern block also contains Koogah Formation rocks as well as important outcrops of Werrie Basalt. Away from the vent site, there are uniform clay soils on ridge tops, duplex soils on mobile sandy slopes and alluvial soils on the deeper layers, with colluvial sandy clay on the valley floors."
From the information sign at the site:
"The first European to observe this smoking mountain was a local farmhand named Mart in 1828 who interpreted it as an active volcano.
Extensive guesswork followed until geologist Rev Wilton correctly identified the phenomenon as a burning coal seam in 1829. Other scientific observers to visit the area over the next 70 years included Lieutenant Thomas Mitchell (later to become Sir Thomas Mitchell), the surveyor W B Clark and Professor Edgeworth-David.
Research shows that this slow burning coal seam ignited around 6,000 years ago near the Pages River, about 6km north of here and has been continuously moving southward at about 1 metre per year.
Its heat haze and sometimes wisps of smoke can be seen on the summit and the permanent thermals of rising warm air attract Wedge-tailed Eagles, which can often be seen soaring above. Families of Eastern Grey Kangaroos nestle on the warm hillsides on cold days as did the Aboriginal people in days gone by.
The area which is presently burning (2009) has many openings, allowing an intake of cool air through the cracks to the fire below.
The intake of air appears to have resulted in a blast-furnace effect being added to the natural burning of the coal and its gases about 30 metres below the surface, bringing the temperature up to around 1700ºC.
Cracks are continuing to open up in the area ahead of the fire as rocks collapse and leave a gap.
Heated fumes coming from the burning area contain iron oxide, alum (potassium aluminium sulphate) and a high-temperature form of quartz coated with iron sulphide. It is this sulphide that gives off the strong sulphur smell.
The white substance covering the surface of the vent area is not ash but old sinter, caused by turning the emerging hot gases of sinter coming from the chimneys into a solid form as ti cools. In the surrounding area you can see the white alum, the red iron oxide (ochre) which was used by the local Aboriginal people for a wide range of purposes and the yellow sulphur used for thousands of years to treat medical conditions. Together they make a colourful palette."
And there is an Earthcache, and a couple of geocaches to find while up there.