Ridge Hill Shelf facts for kids

The Ridge Hill Shelf is a special kind of landform, like a flat area or a step, found at the bottom of the Darling Scarp. The Darling Scarp is a long, low cliff or ridge that runs along the coast in southwest Western Australia.

What is the Ridge Hill Shelf?

The Ridge Hill Shelf is a unique part of the land in Western Australia. It's like a natural shelf or terrace that sits at the base of the Darling Scarp. Imagine a long, low cliff running parallel to the ocean – that's the Darling Scarp, and the Ridge Hill Shelf is right at its foot.

How Did the Ridge Hill Shelf Form?

This landform was created a very long time ago, during a period called the Pleistocene epoch. Back then, the sea level was much higher than it is today, and the ocean reached further inland, closer to the Darling Scarp.

The powerful waves and currents of the ocean caused coastal erosion. This means the sea slowly wore away the land, especially the scarp itself. As the waves crashed, they broke down the rock and carried away sand. This sand then piled up to form large sand dunes. Over time, these sand dunes hardened into a type of rock called eolianite.

The erosion also affected the ironstone of the scarp, which is a rock rich in iron. This process created a special kind of sandstone that has a lot of iron in it, often topped with a hard layer called laterite. The iron gives the sandstone a dull purple-brown color. Depending on how much iron is in it, the rock can look yellow, purple-brown, or a mix of both.

How Big is the Ridge Hill Shelf?

The Ridge Hill Shelf is usually about 76 meters (250 feet) high. Because it's elevated, water drains away easily, which is good for the plants that grow there.

It's important to know that the Ridge Hill Shelf is not the same as the entire foothills of the Darling Scarp. The foothills are much wider, about 15 kilometers (9 miles) across, and they stretch continuously. The Ridge Hill Shelf, however, is much narrower, only about 3 kilometers (2 miles) wide, and it's not continuous; it appears in separate sections.

What Plants Grow on the Shelf?

The Ridge Hill Shelf is mostly covered by a forest. The main trees you'll find there are the Eucalyptus marginata (Jarrah) and Corymbia calophylla (Marri).

Below these tall trees, there's a layer of smaller plants and shrubs, called the understorey. This includes plants like Banksia, Casuarina fraseriana (Western Sheoak), and Xylomelum occidentale (Woody Pear).