How is a sea stump formed?

We will use diagrams to show this in the interactive lesson space - and also run through what key terms the examiners will look for.

As with a lot of physical geography, the key thing to learn is the sequence that leads to the formation of the sea stump.

Sea stumps are formed through coastal erosion of headlands, so that's where we shall start - the headland.

The cliffs of the headland contain several cracks - or to be more scientific, faults or joints. These are weak points in the cliff and are prone to erosion from waves. Two processes of erosion combine to widen the cracks. These are hydraulic action: where the water is forced in to small cracks, pushing air into these spaces and causing the surrouding rock to break off; and abrasion: where the waves smash rocks against the cliff face, causing the weaker spots (faults) to break up.

As a particular fault widens, the erosion continues deeper in to the cliff face until a cave is formed. The same processes of erosion continue to widen and deepen the cave until it opens up at the other side of the headland - this means that the cave has now become an arch. A great real-world example of an arch is Durdle Door near Lulworth in Dorset.

This area of the headland has become progressively weaker as the base of the cliff has been removed. Erosion continues to target the base of the arch, weakening the support for the top of the arch. In addition, weathering processes such as freeze-thaw, chemical weathering and biological weathering through roots and animals weaken the rock at the top of the arch.

When the base and the top of the arch become too weak, the top of the arch collapses instantly in to the sea. This leaves a headland with a column of rock separate from the mainland, this is a sea stack. Further erosion and weathering of the sea stack leads to the formation of a sea stump.

 A fantastic real-world example of this is Old Harry and his missing wife at Handfast Point in Dorset. Harry's wife exists on maps of the area from the Victorian era - but she has unfortunately now been completely eroded away, leaving poor Old Harry (the stack) on his own!

The key sequence that you will be expected to understand is crack (fault) -> cave -> arch -> stack -> stump. Then to achieve higher marks, you will be expected to explain how the various landforms are created in sequence by explaining the erosion and weathering that is taking place. Use of a real-world example is always good as 'Geography is all about REAL PLACES.'

Answered by Rhys W. Geography tutor

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