Fraser Island – World’s Largest Sand Island

Fraser Island is a remarkable natural setting that has received recognition from the United Nations Educational, Scientific and Cultural Organization (UNESCO) as a World Heritage Site. In granting this designation, UNESCO said,

Fraser Island lies just off the east coast of Australia. At 122 km long, it is the largest sand island in the world. Majestic remnants of tall rainforest growing on sand and half the world’s perched freshwater dune lakes are found inland from the beach. The combination of shifting sand-dunes, tropical rainforests and lakes makes it an exceptional site.

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Fraser is a good-sized island but it’s hardly one of the largest. In fact it’s only the fourth largest even in Australia. However, the truly remarkable aspect is that it is formed entirely from sand, shaped by forces of nature over thousands of years. Wind and waves pushed dunes on top of dunes, held in place by the roots of lush vegetation clinging to the surface. Until quite recently the island sustained a logging and a sand mining industry but Australia now protects this wilderness as part of its Great Sandy National Park, just up the coast from Noosa Heads. The island includes a 75 mile beach of packed sand that provides a smooth surface for driving or even aircraft runway (cars must yield the right-of-way to oncoming aircraft in case you ever find yourself in that situation). However the most interesting aspect may be its abundance of unusual freshwater lakes.

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Lake Boomanjin is a rare example of a perched dune lake. There are only about eighty of them on the planet and forty of them are found on Fraser Island. A perched dune lake forms when wind blows an indentation in the sand that then gradually fills with decaying vegetation. Over time the decaying organic matter creates a watertight mat that eventually permeates the sand to form something similar to concrete, almost like a swimming pool. Lake Boomanjin is the largest lake of this type in the world at 190 hectares. Elsewhere on Frasier Island can be found Boomerang Lake, the world’s highest perched dune lake at 130m above sea level.

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Lake Wabby is an example of a barrage lake. Exposed sand on Frasier Island forms into dunes, and the dunes migrate through the power of wind over time. If a dune blows across the path of a stream or another source of water, it acts as a dam and a lake forms behind it. Notice the large dune that created Lake Wabby to the right side of this satellite image.

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Finally, the Manoolcoong Lakes are example of window lakes. These types of lakes form when the wind carves a dent in the sand that extends below the water table, forming a “window” onto what would ordinarily be a subterranean world. The exposed water table appears on the land surface as a pool.