Kungani iGeotrail? Why the Geotrail?
The geotrail has been developed to preserve this geological heritage through building awareness and interest amongst local stakeholders and tourists – both local and international. It is a matchless geological resource.
Stranger in a strange land – the Barberton Greenstone Belt
If you were able to visit Archaean Earth you would indeed be a stranger in a strange land. Earth in the Archaean would have seemed like an ocean covered alien planet; a dim sun hung in the sky, the atmosphere was toxic and almost without oxygen. There was no vegetation, volcanic eruptions filled the sky with ash, a hail of volcanic debris fell for kilometres around the many volcanoes. Torrential downpours lasting millions of years lashed the surface. The moon hung much larger in the night sky –– it was closer and so tides were higher, more frequent and the days were shorter.
The Archaean spanned some 1.5 billion years –– ~2.5 – ~3.8 billion years ago –– and at its end the Earth had been transformed from a wholly oceanic planet to one with plate tectonic activity, ocean basins filled with sediment, volcanic island arcs, continental collisions and rifts tearing the newly-formed crust apart. Deep oceanic basins, evidenced by today’s banded iron formations, chert beds, chemical sediments and pillow lavas, had been formed by tectonic activity. Simple life forms such as cyanobacteria, some of whose remains are found in the black cherts, had evolved. Some cyanobacteria formed mats, seen in sandstones along the trail, some used light for energy, others used sulphur escaping from deep vents on the seafloor or in hot springs on the surface.
The Barberton Greenstone Belt is the best-preserved example of a 350 million year sequence of Archaean Earth rocks –– the Barberton Supergroup. These staggeringly ancient volcanic and sedimentary rocks are a unique record of Archaean Earth between about 3.2 and 3.57 billion years ago. The rocks are of three main groups:
- Onverwacht –– some sedimentary but mostly volcanic rocks ~14 km thick
- Fig Tree –– deep-water sedimentary rocks ~7 km thick
- Moodies –– shallow-water sedimentary rocks ~2.5 km thick
The rocks are a record of cataclysmic volcanic activity, a boundless ocean, racing tides, immense asteroid impacts and the birth of the first continent –– the Kaapvaal craton –– and some of, or perhaps even the earliest, life on Earth. A growing global network of geologists descend annually on Barberton to search for clues to the Archaean eon. Over 30 years of research have helped to define, among other things: the evolution of Earth’s atmosphere; the origins of life; the growth mechanisms of continents and the composition of the earliest oceans. Although rocks of similar age and even older are known from other parts of the world, none combines the outstanding and diverse characteristics of the Barberton Greenstone Belt –– a fame more significant and far longer-lasting than its colourful gold-rush past.
A well-illustrated guidebook to the geotrail, written by Tony Ferrar and Professor Christoph Heubeck, is available from the Barberton Community Tourism office in Barberton.
World Heritage sites – What & Why?
In 1972 the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site adopted the Convention Concerning the Protection of World Cultural and Natural Heritage. The programme catalogues, names, and conserves sites of outstanding cultural or natural importance to the common heritage of humanity. These sites may be forest, mountain, lake, desert, monument, building, complex or even a city . One hundred and ninety states have ratified the convention.
The Barberton Greenstone Belt has been short-listed as a tentative World Heritage Site. The Barberton Makhonjwa geotrail takes you on a journey to this ancient Earth.