Characteristics of granite landscapes The main landforms found in granite areas are tors (see photograph of Saddle Tor, above) Over time the material above an area of granite is weathered and removed by rivers and glaciars. This reduces the pressure on the granite beneath, causing cracks called joints. Rock with joints close together are weathered and broken down more quickly than sections with fewer joints, meaning that they are weathered more slowly than surrounding rock. As the weathered material is removed over time, it leaves rocky outcrops sticking out of the surface. A more in-depth explanation can be found here. However, this is for A Level students, so a more simplified description should be sufficient for GCSE level. http://www.dartmoor.gov.uk/learningabout/lab-printableresources/lab-factsheetshome/lab-torformation Due to the impermeable rock and the high rainfall in many granite areas, the soil is waterlogged and acidic. This leads to moorlands, marches and bogs with low-growing vegetation, as can be seen in the photograph above. Deep, steep V-shaped valleys are also formed by streams eroding cracks in the rock. Uses of granite landscapes Granite is quarried and used as building stone. For example, Aberdeen is known as the Granite City due to the amount of granite used in building construction. Granite areas have poor soils unsuitable for arable farming or dairy farming, but they can be suitable for rearing livestock. The impermeable rock makes granite areas suitable for reservoirs. The unique landscapes of granite areas also attract tourists, as we will look at in more detail in the Dartmoor case study, found in the Teaching Ideas section. Sources: S-Cool (2015) Rocks and landscapes: Granite. [Accessed on 11/08/15] Availablefrom: http://www.s-cool.co.uk/gcse/geography/rocks-and-landscapes/revise-it/granite Dartmoor National Park Authority Geology and Landforms 'Tor formations - Dartmoor Factsheet' [Accessed on 11/08/15] Available from: http://www.dartmoor.gov.uk/learningabout/lab-printableresources/lab-factsheetshome/lab-torformation Coordination Group Publications Ltd. (CGP) (2010) GCSE Geography: The Revision Guide. CGP
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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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