Grysbok Environmental Education Trail
The campus lies on an old marine platform cut by wave action at a time when the sea level was higher than at present (15 million years ago). Three rock types may be encountered on campus. The oldest is a hard grey-white quartzite, known as Table Mountain Quartzite (TMQ), which crops out in several road cuttings. Layers of calcrete, old “beachrock” and dune sand overlie the TMQ. The calcrete is a fine-grained, creamy coloured rock that forms the substrate along the trail. It is formed when groundwater dissolves shell fragments in the sand, which is then precipitated as layers of calcrete. (Note: only the dune sand and calcrete horizons are exposed on the trail). Modern dune deposits occur throughout the area. Most common in the reserve are transverse dunes, with crestlines oriented at about 90 ° to the prevailing winds, which blow from the southwest and east. Also present are parabolic dunes, which form parallel to the prevailing winds. Their shape is influenced in part by vegetation patterns.
The dunefield is about 6000 years old, and forms part of a headland bypass dunefield, which once replenished Algoa Bay beached with sand by overland wind transport. Following the artificial stabilisation of the dunefield in 1870, the headland bypass system was fixed by plant growth and is now largely inactive.
The Geology of an area is very important because it directly shapes plant communities. The plants, in turn, determine what types of animals can survive in the area. As the name "Dune Fynbos" implies, much of the trail lies on an old dunefield.
Tel: +27 (0) 41 504 1111
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PO Box 77000, Nelson Mandela Metropolitan University
Port Elizabeth, 6031, South Africa
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