Caves, blowholes, geos, stacks and arches: a classic coastline of erosion at Eshaness, Shetland The outer coast of Shetland is one of the best places in the world to study the erosion of hard rock coasts. 1. Why is this? A. Wave energy B. Rock type (http://www.fettes.com/shetland/Geology_Shetlland/Images/geology%20sketch%20map.jpg) 2. The Grind of the NavirThis headland at the north end of Eshaness is formed in flows of ignimbrite, a resistant volcanic rock (Figure 1.). What is the dip and strike of the flow? Figure 1. The Grind of the Navir viewed from the south. 3. Geos and caves On Google Maps you can see that the cliffline is indented with many clefts or geos. A. Calder’s or Calders Geo Locate this and estimate the length of the geo. B. Look at http://www.fettes.com/shetland/geo.htmHow do geos form? Refer to hydraulic action and rock fracturing. C. The Holes of Scraada Locate this. How long is this sea cave? How long is the geo? Suggest how this cave formed. What has happened to it subsequently? \\Nfuse1\wwwroot\Geography web\Coasts\Geos_caves_etc.doc 1
4. Blowholes or gloups This diagram of The Grind of the Navir shows a blowhole. What is it? Photo A shows that the headland is crossed by E-W and S-N trending fractures. Suggest how the blowhole might have formed. 5. The Dore Holm: arches A. Find and insert a good image of this island and its arch B. How have rock type, rock structure, wave energy and wave refraction combined to form this impressive feature? 6. The Drongs: stacks A. Find and insert an image of these stacks B. The rock type is granite. What names is given to the sets of vertical fractures that determine the walls of the stacks? C. Why have only stacks and no arches formed at The Drongs? \\Nfuse1\wwwroot\Geography web\Coasts\Geos_caves_etc.doc 2