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257 Pangaea Puzzle What to do: Arrange the plates to match some period of time in the past or present and then press the button to watch the continents drift. What happens: The exhibit’s plates float on compressed air. The real earth’s crust is made of rocky plates which float on the soft mantle below. HOW IT WORKS 1. The exhibit gives you an idea of what has happened to the earth’s continents over the past 200 million years. The exhibit’s continents drift apart on a layer of air – the real continents have ‘floated’ slowly apart on the semi-molten rock underneath the earth’s crust. PE EURO NORTH AMERICA A IC FR A H A T U IC O ER M A S AUSTRALASIA ANTA CA RCTI 2. A super-continent in the geological past was suspected by early map-makers 400 years ago – the shapes of the South American and African coastlines on opposite sides of the Atlantic Ocean look as if they could have fitted together. ATLANTIC OCEAN 3. Alfred Wegener (Germany, 1912) showed that the rock formations were also the same along each coast – even the same sort of fossils - and said the continents must have drifted apart. He coined the name ‘Pangaea’ for the super-continent, from the Greek words for ‘all of the earth’. 4. Continental drift was not accepted by the entire geological community until the 1950s when it was shown that the Atlantic Ocean was widening by a few centimetres each year as new rock slowly wells up in the sea-bed. This is about the same speed as your fingernails grow. The Mid-Atlantic ridge has the same shape as the opposite coastlines! Pangaea - that's it all the earth! 5. We now know that the earth’s solid surface is made up of about 12 plates which move around as a result of convection currents in the semi-molten rock underneath them. Heat is being generated by natural radioactivity deep in the earth to keep this process of movement continuing. 6. If the continental plates are moving apart under the oceans, they must be colliding or sliding along each other in other places! The India plate has been moving north Eurasian under the Eurasian plate for the past 50 million years, The Eurasian plate has buckled and risen to form the Himalayas. Mount Everest is still rising and moving north at a few centimetres per year. Indian plate moves north over millions of years and crashes into the Eurasian plate PERMIAN 225 million years ago plate JURASSIC 135 million years ago India tains moun Plate A PRESENT DAY Plate B 7. The regions of the earth where the plates meet are generally unstable, with frequent earthquakes, tsunamis and often volcanoes. All the mountain ranges have resulted from colliding plates, where one slides past, or under the other and crumples it along the edge. The mountains of Central Thailand were probably formed at an early stage before the break-up of Pangaea. STUART STREET CARDIFF CF10 5BW T 029 20 475 475 8. Pangaea was the most recent super-continent, breaking up 200 million years. Geologists have been able to identify two previous epochs when similar continental drifts occurred. They predict with some confidence (through computer simulations) that the present continents will continue moving and make a new Pangaea in about 250 million years time. F 029 20 482 517 www.techniquest.org