One of the dominate features of the coastline of the southern Fleurieu Peninsula is the movement of the southern ocean along the shoreline. My access to the shoreline is set by the tides and the waves. The sea dumps the dead birds and fish, the seaweed, shells, and the flotsam on the beach or amongst the granite rock, and it then washes them away.
It is the sea as well as the winds that represents the flux of the shore, and shifts the sand on the beaches at Petrel Cove and at Dep's Beach. The sea is also an ever-present danger.
Despite the Fleurieu Peninsula having a long geological history there are no fossils of extinct boneless animals in the rocks along the granite coast, as is the case amongst the limestone cliffs of the treeless Nullarbor Plain.
However, the sea has been a crucial in the land-forming process in the Fleurieu Peninsula's geological history. What largely accounts for the shape and extent of the Fleurieu Peninsula and its Inman River catchment was glaciation of Antarctic proportions that occurred about 300 million years ago when the Antarctic continent was welded against southern Australia. The Peninsula was shaped by the folding and faulting from the Permian glaciation, which affected much of Australia around 300 million years ago.
The ice mass ground its way across the Fleurieu landscape, and it was channelled through the pre-glacial bedrock valley, such as the Inman Trough. The Peninsula and its Inman River catchment was overridden by a continental ice sheet from the south west, and it moved in a northwesterly direction carving through and across the bedrock.