Sandstone (sometimes known as arenite) is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earth's crust.
Sandstone forms over the course of centuries, as deposits of sand accumulate in rivers, lakes or on the ocean floor, and the sand blends with calcite or quarts and then undergoes compression. After enough time goes by, the pressure pushes all of these elements together to create sandstone. Because not all sand is identical but instead comes in a variety of colors and grain textures, each formation has a unique appearance.
Up until the 1940’s it was a prominent landmark, tourist attraction, natural wonder and picnic spot but is now a single large rock and a pile of smaller scattered rocks. Unfortunately it was dynamited in the 1940’s by the South African War Department. Someone idiotically determined that it blocked the trajectory of the gun placed at the headland to protect the Port of Durban from German u-boats during World War 2. It is really sad that such an interesting feature was destroyed.
Along most of the KZN coastline you will notice alternate bays and headlands. These form where alternate layers of hard and soft rock allow the sea to erode the soft rock faster, forming a bay but leaving hard rock sticking out, known as a headland. The alternating rate of erosion of hard and soft rock is known as differential erosion. Areas on a stretch of coast that have small cracks and joints on them are particularly susceptible to attack from waves, along with bedding planes that lie in line with the direction of the waves. These areas will be eroded very quickly. Arches such as the original Cave Rock can form in one of two ways. The first way is when the wave action simply erodes a crack in the rock and causes it to collapse. Alternatively, the area below the crack or joint is undercut and a small cave will form. If the cave forms on a headland, then on the opposite side of the headland, a second cave can also begin to develop simultaneously. The water erodes the cave via corrosion and hydraulic action, flooding the cave and swilling around it, widening the cave and creating a unique pattern on the surface of the cave. As the two caves are eroded and cut into the headland, they will eventually meet. The resulting, iconic, landform is then referred to as an arch. The roof of the arch has no support however and is highly susceptible to weathering via exfoliation, salt crystallization and biological weathering. As the weathering continues, the roof of the arch will collapse. It is possible that Cave Rock initially formed as a result of wave action where a crack or weakness on the rock resulted erosion and caused the rock to be cut off from the rest of the headland by one of these two mechanisms.
Questions:
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If Cave Rock hadn't been blasted to bits what do you think would have happened over time to the rock as a result of wave action?
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Do you think that the ocean or people are the greatest threat to Cave Rock? Look at both the seaward and landward sides in order to substantiate your answers.
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(Site based question) What man made features are present on the top of the rock?