Geology of Remarkable Rocks on Kangaroo Island

Remarkable Rocks

Remarkable Rocks are one of South Australia's famous geological features. The Rocks consist of granite which happens to be the same age as the granite which exists at Cape Willoughby and Victor Harbor. The unusual shapes of these rocks have been created by the weathering action of rain and wind over many 1000's of years.

Process:

As we know there was a layer of granite injected into the sedimentary rock layer where it crystallised a few kilometers below the earths surface. Over the many 1000's/millions of years, rain has continually infiltrated through the cracks in the granite which has eventually decomposed the surrounding rock.

The land surface was then lowed via erosion leaving corestones exposed as unweathered granite.

These corestones (which were solid granite boulders) were/are shaped by the rain and wind, which has formed overhangs, gullies and caves. All of these shapes can be seen today.

Why are the Remarkable Rocks shaped that way?

There is a theory floating among some of the Travelwild staff about the reason as to why these rocks have fascinating shapes. If the granite present at Remarkable Rocks is the same as the granite at Cape Willoughby and on Granite Island, then why don't they have rocks shaped like this?

The solid granite boulders which are exposed on this rugged coastline are shaped by erosion but there is more to it. The most predominant wind direction at Remarkable Rocks is from the south which is unobstructed. Over many millions of years these rocks have suffered a hammering from the wind and rain and it is these two elements which have shaped the rocks.

When it rains here the rocks obviously become wet but due to the predominant south wind, this side (the sea side) is able to dry out, whilst the other side is more protected form this drying wind so therefore it stays wetter for longer. Over time the north side stays much damper and so the rocks become weaker and therefore it means they are likely to break off and create weird shapes.

This is a very rough diagram (adjacent figure) of what may be happening, perhaps use this theory in your tour and see what others come up with? Because why aren't all rocks along the southern coast shaped like this?

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Kangaroo Island Travel Guide

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