GCSE Geography: Coasts - Caves, Arches, Stacks & Stumps

24th August 2017

GCSE Geography Revision - Made Easy!

Everything you need to know about Caves, Arches, Stacks and Stumps on Coasts!


Erosion and weathering are the processes of wearing down materials like rocks. This happens continually along coastlines, creating varying landforms and coastal features. Headlands and cliff faces can go through many different cycles of erosion (see our music video on "Cliffs, Wave-Cut Notches and Platforms", and "Headlands and Bays"), and this is another. Caves, arches, stacks and stumps (in that order) are erosional landforms that can be seen scattered along many coastlines.


Here is an explanation of the erosional cycle:


1.  CAVES - Caves are formed when a crack has appeared in a headland. Even though the crack may only be very slight, the sea will naturally find its way into the crack. As the waves enter and then move out of the crack in the rock, the sea erodes the rock, but also creates and releases air pressure inside the cliff very quickly. This is called hydraulic action, and this force will erode the crack to such a point that it becomes a cave. A great image of this can be found in Verse 1 of our music video accompanying this.


2.  ARCHES - When a cave continues to grow as a result of erosion, the sea water may find its way to breaking through the other side of the headland. This creates an archway, hence the name, in the middle of a headland. Only small to begin with, the arch will continue to grow taller and wider over time as erosion and weathering continue to do their job.


3.  STACKS - Eventually the arch will grow so big that the top of the arch will not be able to support itself anymore. When that time comes, the top of the arch simply collapses. Naturally this leaves the cliff face on one side, and a tall column on the other side, which is called a stack.


4.  STUMPS - Just as with the other processes, a stack is prone to erosion by the sea, and after a period of time, the sea will ahve worn away at the base of a stack just enough that the main body of it collapses. Similar to if you cut down a tree near its base, all that's left is a stump that usually just pokes up above sea level.


This process is a continually recyling one, where as soon as an arch collapses and a stump and cliff face is left, the cliff face will start the whole cycle again, where a crack is exploited by the sea and erosion begins all over again.


A great case study to use in your exam are the Old Harry Rocks along the Swanage coastline, near the Isle of Purbeck. Here you can see every type of erosional landform included in this cycle.


Make sure to check out our music video on "Caves, Arches, Stacks, and Stumps", try to remember every lyric, and then have a go at our test!


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