9 Rock Formations & #49364D

Travelling through South Africa with its remarkable variety of landscapes, one can’t help noticing the unusual rock formations along the way, some of which are part of sites of unique geological importance. In recognition of this rugged and extraordinary beauty, the South African Post Office will issue a set of 10 stamps and two commemorative covers on 8 August .

South Africa’s sites of unique geological importance are as diverse as the Drakensberg Mountain range and the platinum ores of the Bushveld Complex. The formation of the various rocks can largely be ascribed to three processes:

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Sedimentary rock is formed from material that has over many years, sometimes millions of years, been laid down by wind and water erosion. The rivers carry the soil to the ocean where it is deposited. Over millions of years the sediment compacts, and due to heat and other factors, form into rock. Sandstone, limestone and shale are examples of sedimentary rock.

Igneous rock is formed from lava or volcanic activity. The molten rock cools at different rates, causing a variety of rock types to form. Sometimes the rock cools extremely slowly and thus remains underground. Diamonds may form under such conditions. Granite, basalt and andesite are examples of igneous rock formations.

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Metamorphic rock forms when the rock that has already formed due to either lava activity or sedimentation is reformed under extreme heat and pressure. A good example of this in South Africa is the folded mountains of the Cape where the sandstone formations were turned on their side by pressure and heat, thus forming quartzite. Gneiss, quartzite and schist are examples of metamorphic rock formations.

The stamps, which feature photographs by acclaimed landscape photographer, Koos van der Lende, depict the following sites:

Karoo National Park, Western Cape (igneous dolerite). Some of the world’s most important archaeological sites are located in the Central Karoo, particularly the Beaufort West and Nelspoort areas with their multitude of stone-age sites featuring rock engravings by the earliest hunter-gatherers. The rock formations are examples of dolerite sills, which intrude approximately horizontally into bedded sedimentary strata of the Karoo Supergroup.

Gray’s Pass, Drakensberg, KwaZulu-Natal (igneous rock).The magnificent Drakensberg escarpment is the product of millions of years of sculpting by the elements. The geology of the KwaZulu-Natal Drakensberg is relatively simple, because the various rock layers consist almost erntirely of igneous and sedimentary types, which usually lie horizontally. Gray’s Pass features layered basalt flows from the Drakensberg Group lavas of the upper Karoo Supergroup.

Amphibolite in the Sand River Gneiss, Limpopo (metamorphic rock). Some of the oldest rock formations on earth can be found in the bed of the Sand River. These formations are known as Sand River gneiss. The Sand River gneisses are exposed approximately 10 km east of Musina in the Beit Bridge terrane of the Central Zone of the Limpopo Belt. The exposed rock formations have been dated to 3 850 million years ago.

Olifants River, Limpopo (metamorphic rock). Through the ages, the Olifants River has cut deeply into the ground, leaving a spectacular valley filled with a variety of indigenous flora and dramatic rock formations. The geology in the Olifants River catchment consists mainly of hard rock formations, with the occurrence of the Bushveld Igneous Complex as the most prominent feature.

Augrabies, Northern Cape (igneous rock). Augrabies is derived from the Khoi name ‘Aukoerebies’ meaning ‘place of the great noise’. It is one of the world’s largest waterfalls and when the river is in full flood, great volumes of water move through the 18-kilometre abyss of the gorge and thunder down the 56-metre waterfall. The rocks which form the scarp for the falls are granite, which is an igneous rock.

Ai-|Ais/Richtersveld National Park, Northern Cape (metamorphic rock). This is a place of deep canyons, jagged mountain ranges and extraordinary landscapes reflecting the unusual colours of the rocks and soils. Part of the area is inscribed on UNESCO’s World Hertiage List due to its cultural values. The rocky hills feature metamorphic rocks, which are most probably inter-layered schists, gneisses and quartzites.

Golden Gate National Park, Free State (sedimentary rock). The Eastern Free State boasts some of the most impressive rock features in the world. The Sentinel is the most northern point of the Drakensberg mountains and an iconic symbol of the national park. It is an example of fine-grained sandstone formations of the Clarens Formation, Karoo Supergroup, which are mostly ancient wind-blown dune deposits.

Addo Elelphant National Park, Woody Cape Dunes, Eastern Cape (future sedimentary formations). Stretching from the semi-arid Karoo area in the north, to the coast between Sundays River mouth and Bushman’s river mouth, Addo covers about 180 000 hectares and includes the Bird and St Croix Island groups. Woody Cape dunes are sediments now and will in time, form sedimentary rocks again.

Mapungubwe Hill, Limpopo (sedimentary rock). The ancient city of Mapungubwe, meaning ‘hill of the jackal’, is an Iron Age archaeological site in the Limpopo Province. Mapungubwe Hill was awarded World Heritage Site status by the United Nations Educational, Scientific and Cultural Organisation (UNESCO) in July 2003. The hill features sedimentary rock formations.

Cederberg Wilderness Area, Western Cape (Table Mountain sandstone) The majestic Cederberg is a 100-kilometre long mountain range known for its characteristic jagged sandstone, richly coloured by iron oxides to a deep orange, as well as its curious rock formations and rock art. The Table Mountain sandstone is a group of rock formations within the Cape Supergroup sequence of rocks.

The Artist: Koos van der Lende is a prominent South African landscape photographer who specialises in large format, panoramic, landscape photography. Van der Lende says his goal is to capture the unspoiled beauty of the African landscape and to build up a portfolio of work of wild places before it is lost to urban spread.

References:
www.zulu.org.za
www.berg.co.za/geology.htm
www.heritage.org.za/karoo_heritage
www.southafrica.net
www.sahistory.org.za
www.olifants-river-lodge.co.za/

http://za.linkedin.com/pub/koos-van-der-lende

http://www.cederberg.com/wilderness.php

Acknowledgements:
Prof. Pat Eriksson, Melinda De Swartdt and Vusani Mathada at the Faculty of Natural and Agricultural Sciences