Читать книгу Walks in Silverdale and Arnside. 21 easy walks exploring the AONB онлайн

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Geology

All the hills in the area are formed principally of Carboniferous limestone, comprising the remains of marine life laid down in a shallow sea about 300 million years ago. Towards the end of the Carboniferous period violent earth movements convulsed the rocks. They were folded and broken into the present block and basin structure, although considerable erosion has taken place since. The blocks of limestone have a gentle dip, usually to the south or south-east as at Farleton, but to the north-east at Warton Crag, due to the effects of uplifting and faulting. The north–south valleys are the result of faulting. The Trough is a prominent feature encountered on several walks; this indicates the line of the Woodbine Shale, a bed of mudstone which is softer and more easily eroded than the surrounding limestone. At Trowbarrow Quarry it is easy to see how tectonic movements have caused the rock strata to become almost vertical, or even reversed.

The cave at Silverdale Cove (Walk 2)

The last Ice Age, which ended around 15,000 years ago, left its mark on the area. Ice sheets scoured the rocks, resulting in sheets of smooth limestone that can be seen in many locations. A considerable thickness of ice covered the area, and as this melted Morecambe Bay covered a much larger area than it does now. It is thought that ice in the Irish Sea may have dammed the freshwater rivers to make Morecambe Bay into a gigantic lake. The present-day basins were submerged, and it is easy to visualise the Arnside and Silverdale hills as islands. The fluctuations in sea level left deposits of sediments or alluvium in the flat basins, giving rise, where well drained, to rich farmland, or forming the marshy areas such as Leighton Moss and Hawes Water. Around Hawes Water the substance diatomite can be found, which is made up of the siliceous fossil remains of microscopic organisms. It is a valuable commodity, used for its insulating properties, and was worked commercially at Kentmere in the Lake District.