Formation of the Pinnacles: Accumulation of the Sand


Step 1: The sands which make up the Pinnacles Desert and the Tamala Limestone (which extends along much of the west coast of Australia) originated as beach sand brought ashore by the waves of the Indian Ocean. The sand grains are composed of both quartz (SiO2) (generally originating by weathering of continental rocks and delivered to the ocean by rivers) and calcite (CaCO3). The calcite grains are, for the most part, broken up bits of shell material originating on the shallow continental shelf. There is evidence that the dunes formed along the coast reached heights of up to 300 meters!

Two questions need to be answered: [a] how do we know these sand deposits were deposited by wind (as opposed to water)? and [b] where did such vast quantities of sand come from?


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