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41 desert
42 limestone scenery
43 limestone scenery
44 limestone scenery
45 limestone scenery
46 limestone scenery
47 limestone scenery
48 limestone scenery
49 limestone scenery
50 limestone scenery
51 limestone scenery
52 limestone scenery
53 limestone scenery
54 limestone scenery
55 limestone scenery
56 limestone scenery
57 limestone scenery
58 limestone scenery
59 limestone scenery
42 glacial erosion
43 glacial erosion
44 glacial erosion
45 glacial erosion
46 glacial erosion
47 glacial erosion
48 glacial erosion
49 glacial erosion
41 erratic
42 mount blanc
43 glaciation
44 glacier snout
45 hanging valleys
46 glacier junction
47 sandstone arches
48 sandstone cliffs
49 coastal dunes
41 coastal dunes
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Limestone Pavements are bare limestone rock of slabs of rock (clints), separated by variable-width vertical cracks (grikes). These grikes have developed by weathering and enhanced solution along joints. Composed principally of calcite, limestone is vulnerable to chemical weathering by water (solution) and dissolves easily. In the Yorkshire Dales, exposure of very extensive pavements may be partly an example of the stripping of soil by moving ice during the last glaciation period more than 10,000 years ago. Surface and rain water do not flow far on exposed limestone, but infiltrate rapidly into the rock and soil. Where a joint or intersection of joints has been greatly weathered or dissolved water can pass down through the limestone . A stream travelling over an impermeable rock will very quickly disappear when it has to travel over limestone. These sinkholes can be many metres deep leading down to a series of subsurface features. A shakehole is a depression in the limestone landscape. In some limestone areas there is a covering of boulder clay about two or three metres thick. Shakeholes are formed where surface water washes the boulder clay down into cracks or fissures in the limestone under the boulder clay. They are usually found in groups. Cavers have to dig the boulder clay out to see if there is a pothole of any size underneath. When a stream disappears it travels underground through a complex series of caves and eventually works its way down to a level of impermeable rock or until it reaches the top of the water table. The stream travels along the surface of the impermeable rock until it reaches the surface as a spring. Where limestone lies on top of impermeable rock along a valley there can be several springs formed along the intersection of the two rocks. This is a spring line. During the last ice age huge ice sheets scraped away the soil covered spurs in many valleys in the Yorkshire Dales. Steep cliffs of bare rock were exposed. Because these scars are more liable to frost shattering and other forms of erosion they usually have scree slopes of broken rock below them. Carboniferous limestone is a sedimentary rock formed in the Yorkshire Dales around 300 million years ago. These rocks were laid down on the sea bed and made up of layers of ancient corals and skeletons of sea creatures living in the shallow seas at that time. The bedding planes are the horizontal layers formed as the rocks were compressed under deposits formed above. During the meltwater phase of the last ice age, underground streams eroded vast caverns as huge volumes of water travelled through the limestone. Sometimes the roofs of these caverns can collapse exposing the "underground stream" in a very steep sided gorge. During the last ice age the limestone was frozen to great depths. When the ice melted it carved out valleys over the frozen rock. When the limestone thawed out the surface water was able to infiltrate down through the rocks and the dry valleys were left with no surface water. The ice sheet which covered the area carried with it huge boulders from as far away as Scandinavia. When the ice melted these huge boulders were left sitting on the surface. They are called erratics because they are totally different from the bed rock of the area.
bay beach
a bay
a beach
cliffs
hard and soft rocks
sand dunes
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49 glaciation 1
41 glaciation 2
42 glaciation 3
43 glaciation 4
44 beach
45 edinburgh
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