GEOLOGY
Geology is the study of the Earth’s structure and history.
Geology underpins the provision of resources for people and industry, delivers a wide range of essential services, and helps us understand how we can live more sustainably on our planet.Geology plays an essential role in many areas of the economy.
Economic growth and sustainability requires reliable supplies of mineral resources (including construction material), a dependable supply of clean water and the secure and sustainable production of food.A secure, high quality supply of fresh water is vital to human health and well-being.
Hydrogeologists help meet this need through their understanding of water movement and aquifer behaviour, as well as identifying and mitigating water contamination.
LEARN MORE ABOUT DARLING GEOLOGY
The area is characterised by a relatively flat topography, except for the north-westerly trending “Darling hills”, which separate the coastal plain from the gently rolling topography of the interior.
The oldest rocks are the metasediments (shale, siltstone and greywacke) of the late Proterozoic Malmesbury Group. These occur to the east of the “Darling hills” under sand and soil cover.
The Cape Granite Suite is represented by the Darling Batholith which form the “Darling hills” This batholith includes sixteen different varieties of granite. The granites were intruded into the earth’s crust between 540 and 510 million years ago.
The Klipberg Granite is situated in a prominent hill some 5 km to the northwest of Darling. The Klipberg Granite intrudes into the older granites of the Darling Batholith.
The Colenso Fault, which forms the eastern boundary of the Darling Granite Batholith, is the most prominent structural feature of the area. The Colenso Fault has not been active for more than 500 million years, so there is no need for concern!
The Darling area is world renowned for its large variety of wild flowers. These are particularly spectacular during springtime.
The underlying geology provides nutrients for the different veld types in the Darling area e.g. Swartland Granite Renosterveld and Swartland Shale Renosterveld.
The oldest rocks are the metasediments (shale, siltstone and greywacke) of the late Proterozoic Malmesbury Group. These occur to the east of the “Darling hills” under sand and soil cover.
The Cape Granite Suite is represented by the Darling Batholith which form the “Darling hills” This batholith includes sixteen different varieties of granite. The granites were intruded into the earth’s crust between 540 and 510 million years ago.
The Klipberg Granite is situated in a prominent hill some 5 km to the northwest of Darling. The Klipberg Granite intrudes into the older granites of the Darling Batholith.
The Colenso Fault, which forms the eastern boundary of the Darling Granite Batholith, is the most prominent structural feature of the area. The Colenso Fault has not been active for more than 500 million years, so there is no need for concern!
The Darling area is world renowned for its large variety of wild flowers. These are particularly spectacular during springtime.
The underlying geology provides nutrients for the different veld types in the Darling area e.g. Swartland Granite Renosterveld and Swartland Shale Renosterveld.
MINERAL RESOURCES
- Why do we extract minerals?
- Minerals in ‘green energy’ technology
- Rock, mineral or chemical element?
- Industrial Minerals
- Construction Minerals
Without mining none of the everyday products we take for granted would exist.
If you look beneath the surface, you’ll find that mining has something to do with just about everything that we use. Modern industry, technology and consumer products require a vast array of minerals, both abundant and rare. Their extraction and trade forms a major part of the global economy. As the population and the demand for resources grow, innovative technologies are required to locate and extract minerals and to use them more efficiently.Renewable energy technology uses a variety of chemical elements sourced from minerals:
In Solar (Photovoltaic or PV ) panels, tellurium, selenium, indium, cadmium and gallium are required.In Wind turbines, neodymium (one of the rare earth elements) is required.
A mineral is a naturally occurring substance, with a particular chemical formula and crystal structure.
Chemical elements are atoms with specific properties. Minerals are made up of one or more different elements, and rocks are composed of one or more different minerals.Diamonds, gold, platinum and other metal ores are not the only geological materials that are extracted for their commercial value.
Others are known as Industrial Minerals. Hundreds of these minerals are extracted for an enormous range of uses, some of which can be surprising:- Many people think that paper is made entirely from wood? Not so - it contains a clay mineral, kaolin, as a ‘filler’ and to make it white.
- The world communicates through crystals! Quartz is commonly used in microphones and telephones as piezoelectric crystals that convert sound into electrical signals.
- The glass in a bottle of wine that was purchased in the Cape was probably made from high-grade silica sand obtained from the Cape Flats.
Cape Town and every town and village in the Western Cape requires basic materials for construction and development projects.
These materials include building sand, stone aggregate, gravel, cement and bricks.- An essential ingredient for cement is limestone.
- Brick-clay is used to make bricks.
- Stone aggregate is obtained from hard-rock quarries where it is crushed down to the correct sizes.
- Sand is obtained from quarries or borrow pits.
LEARN MORE ABOUT CONCRETE
Concrete is the second most widely consumed substance in the world after water, and is used in infrastructure projects that are essential for socio-economic development.
Concrete is made of cement, sand and stone aggregate. Cement is made by large companies such as PPC and Lafarge from limestone and other raw materials and research is on-going to reduce the carbon footprint of cement.
Concrete sand and stone aggregate is obtained from quarries or borrow pits.
There are SANS specifications for concrete sand in terms of grain size, grading, clay content etc. and not all sand is suitable for making concrete.
Most of the Karoo, for example, is underlain by shale a fine-grained rock that does not weather into suitable concrete sand. So, concrete sand for renewable energy projects (e.g. wind farms) is imported into the Karoo.
The concrete base for a single wind turbine on a wind farm can use up to 60 truckloads of concrete.
The cost of transport is a significant proportion of the final cost of construction materials paid for by consumers.
In general, Municipalities do not adequately plan for the provision of basic construction materials in their areas.
Concrete is made of cement, sand and stone aggregate. Cement is made by large companies such as PPC and Lafarge from limestone and other raw materials and research is on-going to reduce the carbon footprint of cement.
Concrete sand and stone aggregate is obtained from quarries or borrow pits.
There are SANS specifications for concrete sand in terms of grain size, grading, clay content etc. and not all sand is suitable for making concrete.
Most of the Karoo, for example, is underlain by shale a fine-grained rock that does not weather into suitable concrete sand. So, concrete sand for renewable energy projects (e.g. wind farms) is imported into the Karoo.
The concrete base for a single wind turbine on a wind farm can use up to 60 truckloads of concrete.
The cost of transport is a significant proportion of the final cost of construction materials paid for by consumers.
In general, Municipalities do not adequately plan for the provision of basic construction materials in their areas.
Further Reading
- Geological Society of London, 2014. Geology for Society, 20pp. see: www.geolsoc.org.uk/geology-for-society
- John Compton, 2016. The Rocks and Mountains of Cape Town. Second Edition. Earthspun, Cape Town, 112pp.
- John Rogers, 2018. Geological Adventures in the Fairest Cape: Unlocking the Secrets of its Scenery. Popular Geoscience Series 7. Council for Geoscience, Pretoria, 320pp.
SOME INTERESTING FACTS:
- Modern geologists recognise that continental drift is explained by means of a process referred to as plate tectonics. The break-up of Gondwana took place around 130 million years ago when Africa and South America became separate continents divided by the newly forming South Atlantic Ocean.
- Green Point Common is located on a wave-cut platform formed when the ocean was about 25 metres above its present level (about 1.5 million years ago) and the entire Cape Flats was under the sea with Table Mountain being left as an island. Marine sediments (sand and gravel) and even sharks teeth can be found in places below the Cape Flats.
- Geologically, the rocks of the Cape Fold Mountains (the Table Mountain Group), are also found in the Sierra de la Ventana in the southern part of Buenos Aires Province, Argentina. Alex du Toit, the famous South African geologist, recognised the similarities over 100 years ago and postulated that the southern continents had broken up and drifted apart from the supercontinent Gondwana.
- 20 000 years ago the sea level was about 120 metres below the present level. This was during the last ice age when an enormous amount of water was trapped in the large Northern Hemisphere ice sheets.