Gloup - Geological Feature

Shetlopedia - The Shetland Encyclopaedia

Holes of Scraada, Eshaness from the space

The Gloup, Yell from the space

Gloups (from Old Norse: glup) are openings in the surface rocks which developed behind the cliff face. Smaller ones are also often refered to as blow holes with spray being blasted out during high seas like the spray out of the blow hole of a whale.

Their development is not fully understood but in general it is accepted that the more or less vertical shafts which lead from underlying caves to the openings do follow lines of structural weakness within the rocks. Heavy waves pondering into the caves and thus a permanent and rapid change of high pressure and vacuums with their mechanical power may add considerably to both the cavitation process and the widening of the shaft until bigger parts of the cave's roof do collapse.

A fine and easy to reach example are the Holes of Scraada to the north of Eshaness Lighthouse and between the Loch of Houlland and the coast at the Villians of Ure. An unusual blow hole is "The Cannon" a bit south of Eshaness Lighthouse; here the spray is blasted out sideways from the cliff face back into the sea. Although most of the cave entrances and the tunnel openings are hidden when we look down from the cliff tops, blow holes and gloups remind us that the whole cliff side might be cavitated and "undermined" and therefore unstable in geological terms.

As part of place names the term gloup is kept even in such cases where no parts of the former roof of a cave have survived until today. A fine example is "The Gloup" on Yell which might have collapsed some million years ago.