The most westerly point of the Australian continent, next to the Indian Ocean is called Shark Bay, an area of exceptional natural features and a World Heritage site. Scattered around Shark Bay, especially within Peron Peninsula inside the Francois Peron National Park, are several saline lakes of gypsum, known locally as birridas.
Thousands of years ago, when sea levels were much higher than they are today, birridas were landlocked saline lakes between sand dunes. The water was rich in sulphate of lime that was deposited onto the lake floor. When the sea level dropped, the lakes dried up creating salty hollows, and the sulphate of lime evaporated and became loose, powdery gypsum.