Quartz Fields on Aardvark
Quartz Field are of particular importance in the conservation of the Succulent Karoo due to the unique microhabitat that it creates.
The Aardvark Bioreserve lies in a geological region known as the Cape Supergroup. The rocks found in this region were deposited around 520 to 220 million years ago. With the breakup of Gondwanaland – the ancient supercontinent – around 180 million years ago, great forces was at play in the region. These forces were responsible for forming the Swartberg, Langeberg and various other mountain chains in the region. Water from deep underground came in contact with heat from the interior of the earth, heating the water up to very high temperatures. Evidence of these hot water spots are still evident today at places like Warmwaterberg on the road between Barrydale and Ladismith.
When water is heated to above 300°C, Quartz which naturally occur in the surround rock formations, dissolves in the water. The very hot water with the dissolved Quartz in it starts accumulating in cracks and starts rising towards the surface of the earth. As the water moves closer to the surface of the earth, it moves further away from the internal heat source. This causes the water to cool down below 300°C. The quartz that needed the higher temperatures to dissolve, now returns from solution in water to its solid form. (Think about salt being left behind when sea water evaporates). Over time the crack will fill up with quartz, forming a quartz vein. Due to various erosion processes, the quartz vein is exposed to the surface. The quartz vein in turn also breaks down, washing the quartz crystals downhill where it accumulates to form a Quartz field.
The Quartz field, as seen in this position, is therefore the result of more than 500 million years of geological processes. When compared to the surrounding rocks (mostly sandstone and mudstone) the Quartz field is much lighter in colour. The lighter colour means that radiation from the sun is more reflected than the surrounding landscape. It is quite prominent when you pick up a white piece of quartz in your hand and any of the darker rocks in the other. You can clearly feel the difference in temperature between the two. On a hot summer’s day, the quartz stones can be as much as 10°C cooler than the surrounding rocks.
– Kobus Lubbe & Jane Fourie