A Brief Geological History
Fraser Island lies just off the east coast of Australia. It is part of the Great Barrier Reef of Queensland. Fraser Island is about 125km in length and over 160 000 hectares in area. Fraser Island is the largest sand island in the world. The Great Sandy Strait separates Fraser Island from the mainland. Fraser Island formed about two million years ago. Strong winds and ocean waters carried large amounts of sand from the New South Wales area, depositing it along the coast of Queensland. This sand piled up until the island was formed. The sandy surface of Fraser Island is easily re-shaped by wind and water currents. The many types of sand dunes on Fraser Island vary in size, shape and age. They are being constantly changed by the physical and ever present weathering. Radioactive analysis of Fraser Island's sand suggests its dunes are some of the oldest sand formations in the world.
The Geology of the Rainforest!
Fraser Island offers an outstanding example of biological (organic), hydrological (the scientific study of water on the earths surface) and geomorphological (concerned with the structure, origin, and development of the topographical features of the earths surface) processes. Inland from the beach are majestic remnants of tall rainforest growing on 50-meter tall sand dunes, a phenomenon believed to be unique in the world.
The process of soil formation on the island is also unique, since as a result of the continued and successive overlaying of dune systems, creating soils typical of coniferous, or boreal forests. This has created soil profiles above sand from less than half a metre thick to giant forms more than 25 metres thick with the latter far exceeding known depths of these soil types anywhere else in the world and has a direct influence on plant succession. As you pass through the area there is a clear delineation evident in the progression of plant communities depending upon salinity, water table, age and nutrient status of dune sands, exposure and fire frequency. The low shrubby heaths (‘wallum’) are of considerable evolutionary and ecological significance. Fauna including a number of threatened species of frog, have adapted to the highly specialised acidic environment associated with wet heathlands and sedge lands in this siliceous sand environment.
Your Challenge to claim this cache
Follow the signs to the boardwalk for a short one kilometre stroll along one of the most beautiful rainforest lined creeks on the planet. There is never any need to leave the boardwalk. Enjoy the artwork as you enjoy the scenery.
1) Rainforest Relic - The King Fern. How many millions of years ago (at least) were similar plants found as are found here? How many other places is this plant found on Fraser Island?
2) A Lifeline for a Rainforest - The Climate is created by what four factors? What are the Six plant types pictured on the sign?
3) What do you think creates the green tinges that appear in the sandy bottom of the creek bed?