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About the islands
Some 300 islands exist in
the Vaal valley between where the
 river enters the Dome
crater to where it exits. The unique riverbed configuration
and development of the Vaal, filled with channels and
rapids, attracts visitors and researchers from all over the
world. Exploring the islands by canoe and on foot is a
fascinating activity. Not only are they rich in wildlife and
birdlife, but their history tells the story of central South
Africa and its peoples, wars, industries and ecology. Graeme
Addison, your host, is an author and authority on the
world's rivers, as well as an experienced riverman.
The mighty Vaal River
The Vaal and its many
ancestors have drained the central portions of what is now
Southern Africa for billions of years. Before the Vredefort
blast occurred, rivers were carrying gold dust into the
central Witwatersrand basin. The gold was concentrated by
hydrothermal action (heated water permeating the rock
layers) thus creating the rich gold-bearing ores that are
mined today at tremendous depths down to more than 4km.
Billions of years passed, and a new, vast lake formed in the
centre of the supercontinent of Gondwanaland.
Like the Wits
basin before it, the Karoo basin was an inland sea, formed
by rivers carrying sediments from higher ground. The
sediments solidified, some 10km thick, and the Vaal/Orange
basin began to take shape. Between 150 million and 100
million years ago, Gondwanaland broke up into South America,
Africa, Antarctica, Australia, Madagascar and India. The
Vaal and Orange now found their way to the sea.
The Vaal
today is smaller than it was, its headwaters having been
steadily captured by the Orange. The Parys area of the Vaal
is remarkable, as the river is following old meanders while
cutting down like a young river into the strata and rings of
the Vredefort Dome. It is known as a “superimposed” river, a
feature it shares with the Colorado River in the Grand
Canyon of America.
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