Vredefort Dome – the world’s biggest meteor crater

Two billion years ago a meteorite 10 kilometres wide hit the earth near what is today the town of Vredefort in the Free State, 100 kilometres south of Johannesburg. The impact created a massive crater that can still be seen from space – the Vredefort Dome.

Vredefort Dome
An astronaut photo of the Vredefort Dome, also known as the Vredefort crater. The Vaal River can be seen running from top left to right, with the town of Parys visible in the bend in the river, inside the crater. (Image: Nasa Photo STS51I-33-56AA)

Mary Alexander

The meteorite was a piece of rock bigger than Table Mountain. When it hit the earth, it exploded with a thousand-megaton blast of energy equivalent to bomb fired by a trillion tons of dynamite.

The impact was so powerful it turned, in a single moment, 70 cubic kilometres of solid rock into dust. The turmoil it caused to our planet’s climate may have increased oxygen levels in the atmosphere, allowing multicellular life to flourish.

The oldest visible crater

The world has about 130 crater structures of possible impact origin. The Vredefort Dome is the oldest and largest of these, clearly visible from space.

At 2-billion years old, Vredefort is far older than the Chixculub meteor impact site in Mexico. This meteor strike, 65-million years ago, is thought to be the event that led to the extinction of the dinosaurs.

Vredefort’s original impact scar measures 380km across and is made up of three concentric circles of raised rock. They were created by the rebound of rock below the impact site when the asteroid hit. Most of these structures have eroded away and are no longer clearly visible.

The inner circle, measuring 180km, is still visible and can be seen in the beautiful range of hills near Parys and the town of Vredefort.

In 2005, Unesco – the United Nations Educational, Scientific and Cultural Organisation – named this inner circle the Vredefort Dome World Heritage site.

Internationally, there are 851 World Heritage sites, in 141 countries. Africa has 77 sites and South Africa a total of eight – four cultural, three natural and one of mixed cultural and natural heritage. The Vredefort Dome is a natural heritage site.

South Africa’s other World Heritage sites are Robben Island, the Greater St Lucia Wetlands Park, the Mapungubwe Cultural Landscape, the Cradle of Humankind, the uKhahlamba Drakensberg Park, the Cape Floral Region and the Richtersveld Cultural Landscape.

The Vredefort Conservancy

In 1937, earth scientists John Boon and Claude Albritton Boon were the first to suggest that the Vredefort structure was the scar of an ancient meteorite impact. Since then the site has been studied extensively by earth scientists from around the world.

The Vredefort Dome Conservancy, as it is now known, is not just of scientific value. It also has great scenic beauty, making it an ideal tourist destination.

The Dome Conservancy contains a finely balanced ecosystem made up of open plains, bushveld, mountains and ravines with abundant plants and wildlife. At least 99 plant species have already been identified, of which the world’s largest olive wood tree forest is probably the best known.

It is also an important birding area, with over 450 species already identified. It also has as many identified butterflies as the whole of Great Britain, and is home to rare animals such as the rooikat, aardwolf, leopard and the endangered rock dassie.

The Vredefort Dome site fulfils all the criteria set by Unesco for a World Heritage site. It is of outstanding universal value from a scientific point of view, and is remarkable evidence of an important moment in the earth’s geologic history.

Would you like to use this article in your publication or on your website? See Using Brand South Africa material.