Characteristics of chalk and clay landscapes Chalk and clay is mainly found in the south east and east of England in lowland areas. Horizontal layers of chalk and clay sometimes tilt diagonally, due to tectonic activity. Clay is less resistant than chalk so it is eroded faster, leaving chalk sticking out to form escarpments and wide flat areas where the clay was eroded called vales. Escarpments have steep scarp slopes on one side, and gentle dip slopes on the other. This pattern of vales and escarpments can be seen in this diagram of The Weald in south east England. Chalk is a permeable rock that stores water, known as an aquifer. Clay is impermeable. Water flows through the chalk and surfaces where it meets an impermeable rock. Where the water emerges is called a spring line. Chalk areas also feature dry valleys, which were formed during the Ice Age when the ground was frozen and impermeable, but today the water flows underground beneath the valley. Uses of chalk and clay landscapes Chalk is quarried to use in cement for the building industry. Tourists are attracted to the scenery and enjoy activities such as hiking. The wide, flat vales are suitable for arable farming, livestock rearing and dairy farming. As chalk is an aquifer, it is used to supply drinking water using wells and pumps. Sources: Coordination Group Publishing Ltd. (CGP) (2010) GCSE Geography: The Revision Guide. CGP.
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Characteristics of carboniferous limestone landscapes Limestone is formed of calcium carbonate from the remains of sea creatures and corals on the seabed. There are different types of limestone in the UK:
As the weak carbonic acid in rainwater slowly dissolves carboniferous limestone via chemical weathering, especially as it is a pervious rock which means water flow is restricted to the bedding planes and joints, making them more vulnerable to weathering. At the surface: Limestone pavements are flat areas of limestone blocks called clints, which are separated by weathered joints called grikes. Swallow holes are weaknesses in the rock that have been weathered to form holes. Limestone gorges are steep sided gorges which are formed when a cavern underground collapses. Dry valleys are formed when a river which used to flow on the surface (due to the ground being frozen during an Ice Age or due to a higher water table) now flows underground. Resurgent rivers are rivers that emerge to the surface when the limestone is on top of impermeable rock. This BBC Bitesize video shows these processes: http://www.bbc.co.uk/education/clips/z3jfb9q Underground: Caverns form when water flows through joints in the rock or down swallow holes. Stalactites and stalagmites form in caverns when the dissolved minerals in the water solidify and build up. When they meet they form a pillar and when it flows as a sheet, a curtain builds up. This BBC Bitesize video demonstrates these processes: http://www.bbc.co.uk/education/clips/zjs8q6f Uses of carboniferous limestone landscapes Limestone is quarried for building stone and also used to make cement. Tourists visit limestone landscapes to see the distinctive features, such in the Yorkshire Dales, a case study which I'll look at in more detail in the Teaching Ideas section. Dairy farming and rearing livestock is common in limestone areas, as well as some arable farming, although the soil can be too alkaline. Sources: BBC (no date) Bitesize: GCSE Geography. Rock Landscapes Classroom Resources. [Accessed on 11/08/15) Available from: http://www.bbc.co.uk/education/topics/ztbd7ty/resources/3 Coordination Group Publications Ltd. (CGP) (2010) GCSE Geography: The Revision Guide. CGP.Waugh, D. and Bushell, T (2002) New Key Geaography for GCSE. Nelson Thrones, Cheltenham. p.52 Formation and characteristics of rock typesRocks are classified into three types depending on how they are formed. They are igneous, sedimentary and metamorphic. Igneous Igneous rocks are formed when magma from the mantle cools and hardens. If it cools underground, it is intrusive. This cools slowly and forms large crystals and a coarse texture. If it cools above ground after a volcanic eruption, it is extrusive. This cools quickly and forms fine crystals and a fine texture. Igneous rock can form a batholith, a dome of rock formed by large dome of magma cooling. Igneous rocks are tough and resistant to erosion. Example of igneous rocks in the UK are granite and basalt. Sedimentary As the name suggests, these rocks are formed when layers of sediment at the bottom of a sea or lake are compacted. This process is called lithification. The sediment comes from the shells and skeletons of dead sea creatures, as well as eroded material from rocks. Although some sedimentary rocks are tough, such as limestone, most are weaker than igneous and metamorphic rocks. Sedimentary rocks often contain fossils and UK examples include limestone, chalk, clay and shale. Metamorphic Metamorphic rocks are rocks that have “morphed” due to heat and pressure: Rocks deep in the Earth are changed by the pressure on them. Tectonic plate collisions create heat and pressure which changes the rocks. Heat from magma causes rocks to change The rock becomes harder and more compact after the change, so more resistant to erosion. For example, limestone becomes marble and clay becomes slate. The formation of all these rock types is linked by the rock cycle (see left). Distribution of rock typesThe map below shows the distribution and ages of rock across the UK. Here we can see the upland-lowland differences in geology. The lowland south and east is made up of much more recent sedimentary rocks, whereas as the upland areas in Scotland, Wales and northern England are dominated by older sedimentary rocks, and metamorphic and igneous rocks which are more resistant to erosion. These different rock types have shaped the landscape of the UK not just through the physical features they form, but through the impact they have had on how humans use the land and how that in turn changes the landscape. Sources: The Geological Society. (no date) Rock Cycle Processes. [Accessed on 05/08/15] Available from: http://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3446.html Coordination Group Publications Ltd. (CGP) (2010) GCSE Geography: The Revision Guide. CGP. |
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