Bryher is the smallest and most north-westerly inhabited island of the Isles of Scilly.
The granite outcrops you can see here are about three hundred million years old. They were formed when molten granite lay under sandstone and mudstone sediments beneath the sea. Collision of ancient land-masses along southern England and Northern France formed a mountain belt, which caused the buoyant molten granite to rise up under the mountains, cooling and crystalliizing.
The Scillonian granite you see now was a few kilometres underground when it gradually solidified over millions of years. The cooling granite was stressed by Earth movements, leading to the flow and alignment of early-formed crystals in the granite, while similar movements after it solidified made joints and cracks. Uplift and erosion of the south west of England exposed the overlying rock and the mountain belt to erosion, and these cracks have since been emphasised and shaped by weathering and erosion, to form the spectacular formations you can see.
Later, erosion by the sea, with all the power it accumulates from unhindered Atlantic winds and the rise and fall of the tides, has led to this deep, steep-sided channel, known as "The Gulf", separating Shipman Head from the rest of Bryher. The Gulf is a startling example of how features formed over millions of years can be shaped by the relentless power of the sea.
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- At the south-westerly end of the channel is a table-like expanse of rock.
- How do you think this formed?
- Why did it form at the level it did?
- What do you think will happen to this area as geological time progresses?
- How wide at its central point would you estimate the channel to be?
- How would you expect the channel to change, if at all, as time passes?
While photo proof is not required, a photograph of you at The Gulf may increase the latitude I'm willing to give you with the answers...!