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Waterfalls and wonder walls.
"As The World Disappears" (5.12b) at Waterval Boven, South Africa.
Photo: Austin Siadak

Enviro Wildfire Services - Western Cape

FALLING ROCKS AS A CAUSE OF VELDFIRES: Awareness & education opportunity: Falling rocks are a recognised cause of mountain fires, and while seldom occuring on Mountain, it happened yesterday in the Skeleton Gorge area above Kirstenbosch. Cavemen made fires for cooking, heat, and security by striking rocks together capable of making sparks. The Khoi San still use two sticks, and when rubbed together for long enough builds up sufficient heat to start a fire. In the case of the Kirstenbosch fire, it is unlikely that the Sandstone boulders that came crashing down caused sparks, but rather that they generated sufficient heat through friction as they slid and struck against other rocks on the very steep slope. During the investigation we found other rocks that came down in the same area and at the same time as this rockfall that did not start fires. There is also evidence of previous rockfalls (many years ago) that did not start fires in this area. There is also evidence that some smaller rock falls happened AFTER the fire started as a result of plants being burnt away, and water from the helicopters removing exposed soil that kept some of the rocks in place.
In the case of yesterdays fire, all the required elements came together allowing a mountain fire to start as a result of the falling rocks. Temperature (approx. 28 °), humidity (impacting on plant moisture), breezy wind, rocks of suitable size (big enough to generate heat when striking other rocks), sufficient open spaces (for grass to be growing amongst the rocks), steep slope (promoted rapid upward heat onto adjoining dry plants), difficult access (preventing firefighting crews and vehicles from getting to the fire scene quickly) all contributed to the starting and spreading of this fire.
In closing, there are over 80 firefighters up on the mountain this afternoon fighting the fire.

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