Tectonic Plates.
It was as
early as 1620 that the English philosopher Francis Bacon commented
on the apparent similarity of the shape of the West coastline of
Africa and the Eastern coastline of South America. However, Bacon
made no reference
that the two continents could have once been joined. In 1858, an
American called Antonio Schneider made the suggestion that the
continents had somehow moved in respect to each other. But, it
was not until 1915 that German meteorologist Alfred Lothar Wegener
(1880-1930) published in his book, 'THE ORIGIN OF CONTINENTS AND
OCEANS' the theory of
Continental Drift
. Wegener proposed that the
earth had once consisted of a single land mass surrounded by a vast
ocean. He named this super continent
Pangaea and explained that it
had long ago divided forming two great continents -
Laurasia in the
North and
Gondwana in the South and that, in time, these two
continents had further divided.
Wegener's theory was viewed
with scepticism by the Geological fraternity until the 1960s by
which time advanced scientific measuring equipment had been
developed and the phenomenon of Paleomagnetism was accepted.
The Paleo-Maps
shown below cover a period beginning 650 million years ago showing the development of the land masses
beginning with the ancient continent of Rodina and continuing through to 50
million years in the future, showing, where it is thought the land mass of
Africa, and Namibia, will be situated should tectonic plate movement continue at
the present rate.
Between 4,000 and
2,500 million years ago the early tectonic plate movements in
the earth's crust began to form the first land masses. In southern
Africa the Kaapvaal Craton stabilized as long ago as 3,000 Ma, and
the Zimbabwe Craton had stabilised by 2,600 Ma. By 1,300 Ma ago
these two Cratons had connected with the Congo and Kalahari Cratons,
and the land mass known as Rodinia was beginning to form.
What's in a name: Gondwana
derives its name from an area situated in Central India, meaning Land of the
Gonds, where a 'tribe' of people known as the Gonds lived. Also in this area of
India is a geological feature that was formed in the early Palaeozoic to early
Mesozoic eras and is referred to as the Gondwana Beds. During the latter part of
the nineteenth century the Austrian geologist Edward Suess, suggested that, on
the basis of comparative geological evidence, the continents of Africa -
Australia - India and South America had once formed a super continent which he
named Gondwana. OK, so if one 'says' Gondwana, it literally means
Land of the Gonds Land, or Gonds-Land Land. It would appear that Gondwana
is the more correct of the two.
Tectonic plate movement caused the land mass to
increase and also move southwards that by the Early Cambrian Period some 500 million
years ago Gondwana had grown into a great continent
comprising of what is now referred to as Africa - Antarctica -
Australia - India - Madagascar - South America - and at one time
even included the American State of Florida and part of Southwest
Europe, with the southern
areas straddling the polar region. From 320 to 270 million years ago
the Great Gondwana Ice-Age covered Namibia. Glaciers
scoured the ancient rock formations and during the melt floods moved
enormous amounts of boulder debris and sediments that in places
would settle to be thousand of metres thick . During this time the
great inland Gai-As sea covered much of southern and western Namibia
and spread into what is now South America. The discovery of
Mesosaurus fossils in both Brazil and Namibia have helped to
support the theory of
Continental Drift . There were later times when vast deserts
covered much of Namibia and extensive volcanism.
Gondwana
began to break about 130 million years ago and the two new
continents of Africa and South America began to drift apart. See the
below Paleo Maps created by Christopher R. Scotese for a better
understanding of the earth's plate movements from 650Ma ago and into
the future 50Ma to see an equatorial Namibia.
The Air That We Breath: The oldest known of fossils in the world are of
the green-blue algae known as cynobacteria that lived at the edges
of the ancient oceans as early as 3,500 million years ago. These
simple algae increased to be the dominant life force on the planet
for most of the Eon of time known as the Proterozoic, and derived
their energy from the sun's rays by the process of photosynthesis.
3,000 Ma ago the earth's atmosphere was rich with carbon dioxide and devoid of oxygen, but over a
period of 1 billion years the activity of these small algae had
increased the atmosphere's oxygen content to about 20% which in turn
allowed for more complex life forms to evolve. These algae with
their glutinous sheaths as protection grew in colonies and carpeted
the sea bed. Grains of sand would cling to the sheath's and
eventually block the sun's light from them. The algae's survival
response was that of growing up through the layer of grains in order
that they could continue with the process of
photosynthesizing. This pattern of early life continued over hundreds of millions of
years and eventually led to the building of the great carbonate mountain
chains. The fossilized remains of these algae 'constructions' are
named Stromatolites and represent the some of the oldest of
all fossils, and can be found in Namibia.
