Geological Features of Byron Bay and the Great Tweed Volcano, Australia On The Move

Geological Features of Byron Bay and the Great Tweed Volcano, Australia On The Move

By Gary Opit

Every year the Australian continent is pulled north 7cm by the movement of white-hot liquid rock that flows 100 km beneath our feet. This means that if you visit Byron Bay once a year, each time it will be 7 cm further north than it was on your previous visit. If you are visiting from another location in Australia, that distance will not have changed as your home will have also moved 7 cm further north. If you are visiting from a location in the northern hemisphere, then Australia will have travelled 7 cm towards your home.


One hundred million years ago Australia was a part of the super continent of Gondwana. This included South America, Africa, and India. Along with dinosaurs, the ancestors of most of the plants and animals that presently inhabit Australia were distributed across that ancient land mass. South America, Africa and India broke away from Gondwana and were dragged north leaving Australia still connected to Antarctica. Around fifty million years ago Australia finally broke loose and was torn away by the relentless flow of liquid rock on which all land floats. The rift cut its way across the land between Tasmania and the mainland creating Bass strait before petering out and so Tasmania was saved from its embrace with Antarctica, which remained straddling the South Pole.


With Australia out of the way, the icy currents of the Southern Ocean were able to continuously encircle Antarctica, producing a planet-sized refrigerator that cooled the Earth until ice age conditions prevailed. Australia moved slowly north into the tropics as the globe cooled and so the climate remained stable, and this allowed ancient plants and animals to survive. As we move into the landscape and forests of north-eastern New South Wales, we are stepping back into time to experience life forms that have existed for many millions of years and that have adapted to continuously changing conditions and so have survived to the present time.


A gigantic, extinct volcano that is centred on Mount Wollumbin in north-eastern New South Wales has its massive crater rim forming the Queensland / New South Wales Border Ranges and the Nightcap Range to the south. It is one of the largest volcanic erosion calderas in the world. Vast flows of basalt lava 23 million years ago filled the valleys of an ancient sandstone mountain range that has long since eroded into the ocean. As the sandstone eroded away it left the erosion resistant solidified lava standing above the countryside creating our often sheer-sided escarpments and plateaus of basalt-rich soil perfect for rainforest and agriculture in our inverted landscape.


The hot spot in the underlying mantle, which caused the molten rock flows to break through the earth’s crust and create the super volcano of Wollumbin / Mount Warning,remained in its position. Our ancient extinct volcano can never erupt because our landscape was created where Victoria is now situated. Our continent continued to slide north above the hot spot in the mantle, taking the eroding remains of the caldera and its associated mountain ranges away from the stationary volcano that now sits beneath Victoria. Vast periods of time can pass between eruptions. The last time it erupted was 5 thousand years ago creating Tower Hill to the west of Melbourne.

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