HomeGeology Fact Sheets Geology Fact Sheets What are birridas? What created the rounded depressions in the sand called birridas? All there is to know about these intriguing geological oddities is in this fact sheet. The Geology of Shark Bay What created the two distinct peninsulas that make up Shark Bay? Where did the local limestone and sandstone come from? Check this fact sheet for all the answers. Why Shark Bay's waters are super salty! The hypersaline waters of Shark Bay are an amazing phenomena that lead to World Heritage listing. Find out how it works here!