#dropstone

Rocks out of place

Why are these rocks out of place? They just do not fit the environment in which they are. The sea waves that moved the medium to coarse sand that is now the sandstone that surrounds these boulders, are not strong enough to move boulders. There is a huge contrast in mass between the sand and the boulder. So, the only explanation is they were placed here by some other means. For this reason, such rocks are called ‘dropstones’, as they were dropped/placed into their current position, rather than being transported along with the surrounding sediment.

One explanation how this could have happened, is the sea ice. During Permian (~300-250 million years ago) this region was under ice age conditions, with glaciers covering the continent from land to sea. So, whether it was glaciers sliding into the sea, or sea ice enveloping loose boulders around the coast and moving them off into the sea; it is impossible to say exactly. But, because ice floats on water, it provides a good candidate for a mechanism of moving these heavy boulders from the land to the sea bypassing the sea wave transport.

Ulladulla, Australia