Gradation Processes

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Gradational Processes

Introduction

Gradation is a process whereby the surface of the land is reduced to an even plain known as grade, higher areas are worn down and depressions are filled. Coastal areas are a great example of the process known as gradation. Our study site Lowlands is a beach located on the south western coast of Australia about 30kms or half and hours drive from Albany. Lowlands beach is an example of the most common coastal landscape, the cliffed coastline of headlands and bays.

Erosional Landforms

The most predominant erosional coastal landforms at lowlands beach are the bays, headlands, wave cut platforms, blowholes and natural arches, and sea cliffs. Each landform has been shaped due to different erosional processes. 

Bays are the result of less resistant sections of coastline eroding at a faster rate than others. Destructive waves and wave transportation is the main cause of this landform. The extent of erosion depends on the effectiveness of waves transporting away the weathered material.

Headlands are predominantly sections of resistant strata within the coastal zone. They may be the result of igneous intrusions that have been exposed as the surrounding rock has been eroded.  The material surrounding the resistant strata is worn back by waves refracting and concentrating energy on the headland; wave erosion as seen in Figure 1.  Over time many other eroded landforms are produced such as, sea cliffs, wave cut platforms, stacks, caves, and natural bridges, where the strata is still intact and uniform.

Wave-cut platforms extend seaward from the base of a cliff or headland. They are relatively flat rocky shelves that may be exposed during low tide. Their surfaces are shaped by the physical and chemical weathering processes of abrasion, hydraulic action and hydration. Rock pools, gutters and potholes are produced due to these processes. Marine vegetation such as seaweed can offer some protection against further erosion of the wave-cut platform. 

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Where resistant rocks form headlands, the sea erodes the coast in successive stages. First it exploits weaknesses such as faults and cracks to form caves. Then it gradually wears away the interior of the caves and enlarges them. In some cases the roofs may be broken through to form blowholes; shown in Figure 2. In other cases the caves at either side of a headland may unite to form a natural arch.

Sea cliffs are common eroded features along exposed coastlines such as lowlands beach. Most sea cliffs will retreat landwards as wave action under cuts their bases. The undercutting ...

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