Where Australia Collides with AsiaWegener never lived to see his theory vindicated as he died in 1930 at the age of fifty
while trekking across the Greenland ice sheet in an attempt to resupply a weather
station.
One hundred and sixty million years ago the supercontinent of Gondwana lay near
the South Pole, where the present continents of Australia, India, Africa and South
America were all connected to Antarctica, which at this time was ice-free. As a result
of this moderate climate a unique Gondwanaland flora and fauna developed, some of
which still survives on these now disconnected continents. About 130 million years
ago changes in the circulation of convection currents within the earth’s upper mantle
started to break Gondwanaland apart. Rifts began to form in its crust like cracks in an
eggshell. Molten volcanic rocks were intruded into the rocks along these rifts which
slowly cooled to form pipes of black dolerite. Millions of years of erosion eventually
exposed these dolerites where, for instance, at Cape Raoul on the Tasman Peninsula
they point across the Southern Ocean towards similar dolerite cliffs in Antarctica.
Gondwanaland began to break up
along these rifts as magma or new oceanic
material welled up through the crust and
spread out as new ocean floor. Around 60
million years ago the oceanic rift between
southern Australia and Antarctica began
opening from west to east, and by 50
million years ago the last land link between
Tasmania and Antarctica was broken.
The separation of the southern
continents from Antarctica allowed
ocean currents to circle Antarctica for the
first time. As a consequence Antarctica
became cooler and ice-bound, while
Australia gradually become hotter and
drier as it moved north out of the cloud
and rain brought by the winds of the
Roaring Forties. Once the continental raft
that is Australia–New Guinea began its
50-million-year voyage north towards the
equator, its cargo of Gondwanan fauna and
flora began to evolve independently of life
on the other southern continents. On this
raft, primitive creatures still thrive, which
are only known as fossils elsewhere on the
Dolerite pillars of Cape Raoul, Tasman Peninsula,
Tasmania, Australia
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