Core Unit 1: Physical Geography - Folding, Faulting & Rocks PDF

Core Unit 1: Physical Geography Contents – Folding, Faulting & Rocks Folding Faulting Rock Types Human Interaction with Rock Cycle Past Paper Questions...

Core Unit 1: Physical Geography Contents – Folding, Faulting & Rocks Folding Faulting Rock Types Human Interaction with Rock Cycle Past Paper Questions H1 Sample Answers W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 1  Core Unit 1: Physical Geography Folding and Faulting Folding is the bending of stratified rocks of the Earth’s crust Faulting is a crack in the Earth’s crust Deformation is when rocks are changed from the original rock structure and these changes are known as deformation e.g. rocks bending, squeezing, stretching or breaking Parts of a Fold Anticline – top part of the fold Syncline – down part of the fold Limb – sides of the fold Force Process Effect Example Compression A body of rock is Folding Destructive Plate squeezed together Faulting Boundaries Tension A body of rock is Faulting Constructive Plate stretched Boundary Shearing Rocks slide past Faulting Conservative Plate each other Boundaries Types of Folds Simple Fold – a fold where both limbs have the same slope Asymmetric Fold – a fold where the slope of one limb is steeper than the other limb Overfold – a fold where the limb of one slope has been partly overturned on the other limb Overthrust Fold – a fold where one limb completely overturns the other limb Period Age Trend Example Caledonian Folding 400 million years Northeast → Wicklow Mountains ago Southwest Armorican Folding 250 million years West → East Comeragh ago Mountains Alpine Folding 60 million years Alps Mountains ago The Alpine fold mountains are the highest in the world today but the Caledonian and Armorican were once much higher than they are today but have been worn down due to denudation Faulting Faulting is a crack in the Earth’s crust W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 2  Core Unit 1: Physical Geography Types of Faults Normal Fault – these result from tension stretches which pull the plates apart and the movement is normally vertical – as one block slips down past the other Reverse Fault – these results from compression. The movement is vertical as one block of rock is forced upwards over the other Thrust Fault - these results from compression. The movement is vertical as one block of rock is forced upwards over the other Tear Fault – these results from shearing. The movement is horizontal as plates slide past each other Type Force Movement Example Landforms Created Normal Tension Downward Constructive Plate Rift Valleys e.g. Fault Boundary e.g. North East African Rift American  → Eurasian Valley Reverse Compression Upwards Destructive Plate Block Mountains Fault Boundary e.g. African→ e.g. Black Forest,  Eurasian Plate Germany Thrust Compression Upwards Destructive Plate Block Mountains Fault Boundary e.g. African→ e.g. Vosges, France  Eurasian Plate Tear Fault Shearing Horizontal Conservative Plate E.g. San Andreas Boundary e.g. Pacific and Fault in California North American Plate Rock – is a solid material made up of one or more minerals Rock Characteristics Minerals – different minerals will make-up different rocks Hardness – rock hardness depends on strong the rocks are cemented together Colour – the colour depends on the mineral content of the rock Structure – some rocks have layers (strata) while others are a solid mass Texture – rocks have different sizes, shape and arrangement of mineral grains Rock Groups Igneous – are formed when molten magma cools and solidifies above or below the crust Sedimentary – are formed from the compression and cementation of sediment remains at the bottom of the ocean Metamorphic – rock is formed when minerals of existing rock are changed through great heat and/or pressure W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 3  Core Unit 1: Physical Geography Rock Group Rock Colour Use Example Igneous Basalt Black Building Giant’s Causeway Granite Dark grey Materials Wicklow Mountains Kitchen Counters Sedimentary Limestone Grey Road Chippings Burren, Co. Clare Sandstone Brown-Red Building Comeragh Materials Mountains Metamorphic Marble Black Fireplace Co. Kilkenny Quartzite Grey Kitchen Wicklow Mountains Counters Formation of Igneous Rocks Igneous rocks are formed from the cooling of very hot molten magma above or below the Earth’s crust Magma is pushed up through the crust from the asthenosphere. Magma rises up because it is less dense than crustal rocks. Also, it rises up as it is squeezed due to the pressure of the overlying rocks Magma has temperatures of over 1200 degrees Celsius and therefore melts some of the crustal rock as it rises upwards Igneous rocks are mainly found at destructive and constructive plate boundaries as the magma is able to escape up through the faults and fissures Magma/lave cools once it is exposed to the cooler temperatures and crystallisation will take place. The speed of cooling will influence the size of the crystals within a rock i.e. if it cools quickly the crystals will be small e.g. basalt and if they cool slowly the crystals will be large e.g. granite Igneous rocks can be intrusive (plutonic) or extrusive, depending on where the magma/lava cools. If the magma cools beneath the Earth’s crust that they’re known as intrusive rocks and if they cool above the Earth’s surface they’re known as extrusive rocks Granite is an intrusive rock and basalt is an extrusive rock that I have studied. Granite is an intrusive igneous rock formed when magma cools slowly under the earth’s surface. As the magma cools slowly, large crystals form in granite Granite is composed of three minerals: mica, feldspar and quartz. The proportions of these minerals vary creating granites of many different colours and textures. However, grey is the dominant colour found in Ireland Granite is a strong, resistant rock used in buildings and in kitchens for countertops. When granite is exposed to rain, it breaks up to form clay An example of where Granite is found in the Leinster Batholith, formed 400 million year ago during the Caledonian folding movement. Magma chambers formed under the surface where the magma slowly cooled to form granite. W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 4  Core Unit 1: Physical Geography Nearby rocks were baked and cooked by the intense heat into metamorphic rocks, e.g. sandstone was metamorphosed into quartz As the overlying layers of softer sedimentary rocks were eroded, the harder igneous batholith of granite was exposed. The Great Sugar Loaf in Wicklow is granite coated with a sprinkle of quartzite, thus the name ‘Sugar Loaf’ Basalt is an extrusive igneous rock formed when lava cools quickly on the surface. Lava escapes through fissures and volcanoes and is cooled quickly by air and water. Thus, basalt is smoother with tiny crystals and a glassy texture and is known as an obsidian rock Basalt is a black, dark-grey rock. It is a very hard rock but is not very attractive, so is usually used in road construction. When basalt weathers, it forms a deep fertile soil as found in the fertile river valleys of Ulster. The Antrim–Derry plateau is a lava plateau in the north-east of Ireland formed when basic, runny lava escaped from a fissure and flowed for many miles. It cooled quickly to form an elevated plateau. The Giant’s Causeway’s hexagonal columns of basalt are a world-renowned tourist attraction. At the Giant’s Causeway, lava cooled quickly in a stream where the water caused the basalt to shrink and contract into the famous hexagonal columns Formation of Sedimentary Rocks Sedimentary rocks are formed when sediments at the bottom of the sea are compressions, compacted and cemented together naturally. Sediments include tiny rock fragments, sand, clay, plant and animal remains The sediments are compressed together by the weight of the overlying sediments. The process of compaction and cementation is known as lithification Sedimentary rocks are usually laid in strata with defined bedding planes between the strata. These series of layers are known as stratification There are three groups of sedimentary rocks – organic, inorganic and chemical Organically formed sedimentary rocks are the compacted remains of plant and animals e.g. Limestone Inorganically formed sedimentary rocks are the compacted remains of pre- existing rock fragments e.g. sandstone Chemically formed sedimentary rocks are formed when water is evaporated from sea area and the sediments are compacted together by the weight of mud and sand into stratified rocks e.g. gypsum which can be found in Co. Cavan Limestone is a sedimentary rock that has joints and bedding planes. Joints are vertical lines of weakness throughout limestone that were formed when the rock was compressed by plate movements. W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 5  Core Unit 1: Physical Geography Bedding planes are the horizontal cracks between layers of sedimentary rock. Water can move easily through limestone, down through the joints and along the bedding planes and down through the joints again. Limestone is slowly and chemically weathered by rainwater in a process called carbonation. As rain falls through the atmosphere and soaks through soil, it absorbs carbon dioxide to become a weak carbonic acid. This weak acid slowly dissolves limestone. This process is very evident in karst areas e.g. the Burren, Co Clare, where limestone rock has been exposed. The Irish limestone was form over 300 million years ago and the limestone is usually grey in colour. The joints are widened and deepened to become grikes. The large slabs of rock separating the many grikes are called clints and the feature is known as a limestone pavement. When rivers flow into karst landscapes they often disappear down through enlarged joints called swallow holes. As the rain percolates through the permeable limestone, down the joints and along the bedding planes, it is also dissolving, by carbonation, and eroding, by hydraulic action, the soft limestone rock. The bedding planes may be enlarged into passages and in time vast caves and caverns are created. Limestone caves contain many dripstone features formed by water containing dissolved limestone evaporating in the warm caves. Stalactites hang from the ceilings of the caves while stalagmites grow upwards from water splashing to the floors of the caves. Pillars form when stalactites and stalagmites join together e.g. Aillwee Caves, Co Clare. In coastal areas, especially near cliffs, where sedimentary rocks are exposed to sea erosion, bedding planes are very quickly enlarged by abrasion and hydraulic action to make sea caves. Waves constantly pounding against the exposed bedding planes and joints quickly form caves. Inside the caves, the joints may be eroded by compressed air, right through the top of the cave to form blow holes. An example of sea caves and blow holes may be found at the Cliffs of Moher, Co. Clare Decayed Vegetation → Coal Sand → Sandstone Plants & Animals → Limestone Formation of Metamorphic Rocks Metamorphic rocks were once igneous or sedimentary rocks. They were changed both physically and chemically by great heat and/or pressure If the rocks were changed because of great heat this is known as thermal metamorphism and this happens when heat from volcanic eruptions changes the rocks it comes into contact with W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 6  Core Unit 1: Physical Geography If rocks were changed because of great heat and/or pressure this is known as regional metamorphism and this happens at destructive plate boundaries e.g. during the Caledonian folding period The process of change from an older rock into a new and different rock is called metamorphism When metamorphism takes place new minerals may form, the rock texture changes, old minerals will change shape, size and arrangement which is known as recrystallisation The colour of rocks may change too due to the chemical reaction that takes place to the existing minerals in the rock. An older rock that exists before metamorphism is known as protolith Examples of metamorphism are Limestone changing to Marble, Sandstone changes to Quartzite, Granite changes to Gneiss and Shale changes to Slate There are three types of metamorphism 1) Thermal metamorphism, Regional metamorphism and Dynamic metamorphism Thermal metamorphism occurs at temperatures between 250-850 degrees Celsius. Magma pushing into the Earth’s crust heats up the rock. This heated contact zone around a magma intrusion is known as an aureole Marble is formed due to the thermal metamorphism of limestone at destructive plate boundaries When the plates collide, limestone is subducted and on entering the mantle it melts forming magma. The magma then rises cooling the surrounding limestone changing it into marble. Marble comes in different colours - the green marble of Connemara or the white marble of Rathlin Island, Co. Donegal. Marble is also quarried at Carrara in Tuscany, Italy It is a highly valued rock with a smooth texture, ideal for building and sculpture but it may be damaged by acid rain. The Taj Mahal in India was built of white marble Dynamic metamorphism occurs at destructive plate boundaries when pieces of crust slip past each other in opposite directions. It is metamorphism resulting from deformation Gneiss is formed from another metamorphic rock, schist. The schist formed from fine grained sedimentary rock, shale and can also be formed from granite It is formed due to great pressure which is regional metamorphism caused as a result of moving plates at destructive plate boundaries It is a tough hard rock comprising of feldspars, quartz and mica and is found in Belmullet, Co. Mayo Slate forms due to the dynamic metamorphism of shale. At destructive plate boundaries shale is put under immense pressure. This pressure compresses the shale into different layers or strata, forming slate W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 7  Core Unit 1: Physical Geography Slate is waterproof and it splits easily into thin sheets making it ideal for roofing but trade in slate has declined due to the greater use of tiles. Slate is found in Kilaloe, Co. Clare Human Interaction with the Rock Cycle outside of Ireland Geothermal Energy – Geothermal energy is energy that is extracted through natural heat from the Earth’s core onto the earth’s surface Iceland is an example of a country that creates Geothermal energy and uses the energy to power 32% of all their electricity Geothermal comes from the Greek words geo which means earth and therme which means heat. Several countries, especially Iceland and New Zealand, use geothermal energy. Iceland’s position on the mid-Atlantic ridge allows it to use geothermal energy to make electricity and to heat water Iceland has five geothermal power plants and geothermal heating provides hot water for 98% of Iceland’s housing. It is such a cheap source of heat that some footpaths of Iceland’s capital (Reykjavik) are heated Geothermal energy uses the rock cycle to provide heat and power. Magma in the mantle pushes its way into fissures in the crust of the Earth and has temperatures of over 1200 degrees Celsius and therefore the magma increases the temperature of the rocks near the crust. Magma near the Earth’s surface superheats water above its boiling point, often reaching temperatures of over 200 degrees Celsius. Temperatures of crustal rocks naturally increases with depth by about 25 degrees Celsius per kilometre Technology has helped to extract the geothermal energy as the Earth’s Crust is drilled from the surface. The hot water/steam can be pumped up through pipes from underground hot water reservoirs If there is a shortage of ground water cold water is pumped into a rock via a series of wells The steam from the heated water is used to turn turbines within a generator which in turns creates electricity As the steam cools, it condense back into water and can be injected back underground to be used again and the cycle is repeated Geothermal energy has reduced the need for fossil fuels and helped reduce harmful greenhouse gas emissions The hot water can be distributed directly to homes and industries to supply hot water and central heating. It is also used to heat greenhouses for vegetable production. In this way Iceland can produce salad crops cheaply and reduce expensive imports 85% of all Iceland’s home use geothermal energy as a heat source which allows for low home-heating costs and stops prices of home-heating fluctuating as they aren’t relying on fossil fuel imports W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 8  Core Unit 1: Physical Geography Geothermal energy is 80% cheaper than the electricity generated from fossil fuels and its significantly better for the environment as it is a sustainable source of energy with very low CO2 emission levels compared to burning fossil fuels which could help to reduce the dangers of climate change In Iceland geothermal energy is also a tourist attraction. One power plant just south of Reykjavik uses mineral rich water from the power station to fill up a nearby lake known as the Blue Lagoon This has become one of Iceland’s most famous tourist destinations and has a spa complex beside the lagoon where the water is kept at 40 degree Celsius for bathers Other effects of geothermal energy are geysers (a spouting spring erupts boiling water and steam every five minutes or so) and geothermal springs which are tourist attractions in Iceland The Geyser area is one of Iceland’s most famous tourist destinations due to the geothermal activity that occurs here. It has several hot bubbling mudpools and geysers which attract thousands of tourists to the area each year Employment is another huge advantage of using geothermal energy as it has created direct and in-direct employment for people in Iceland There are some disadvantages of geothermal energy however as there are high installation costs involved as the equipment and technology use is very specialised e.g. underground pipes The extraction of too much water from the ground may lead to subsidence of the overlying ground surface The are some environmental concerns too as the extraction of geothermal energy leads to the emissions of sulphur dioxide which in turns pollutes our water system Human Interaction with the Rock Cycle in Ireland Natural Gas – Natural gas is energy that is extracted 50 km off the south coast of Ireland at Kinsale Gas Field and the west coast of Ireland at Corrib Gas Field Kinsale Gas field was first discovered in 1971 and it started to be extracted in 1978 and it is operated by Petroleum The Corrib gas field was discovered in 1996 but it wasn’t until 29th December 2015 that production began due to a lot of controversy as locals and activists were very concern about the safety of the project Today, Natural Gas accounts for over 35% of the total energy usage in Ireland The Corrib gas field is over 200 million years old and was formed due to the decaying of vegetation which overtime was compressed and compacted into the sedimentary rocks. The oil and natural gas is found inside the sedimentary rocks W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 9  Core Unit 1: Physical Geography The natural gas gets trapped inside the anticlines and fault traps of sedimentary rocks. Sometimes the natural gas can escape out through the sandy layers but sometimes it is trapped in the anticlines or fault traps Natural gas is then explored by drilling exploratory wells to confirm the presence and the volume of oil/natural gas within the fault traps and/or anticlines The Natural gas is then brought to the Earth’s surface by drilling a hole through the impermeable rock which is keeps the fossil fuel from escaping. The natural gas is held under pressure and once released it moves to the surface by itself Exploration of Natural Gas is controlled by the Irish Department of Energy who issue licences to private developers e.g. Shell, Petroleum and Statoil Ireland’s corporation tax is 12.5% however for the private developers of natural gas or oil they have to pay a corporation tax of 40% to the Irish Government An Bord Gáis controls the distribution of natural gas to industry, business and residential customers in Ireland The Corrib gas field is located approximately 75 km of the coast of Mayo and the natural gas lies approximately 3.5 km below the surface of the sea water The pipes that extract the natural gas in Corrib gas field are located along the bed of the seafloor which brings the fossil fuel inland. The pipeline is linked to the main terminal which is 9 km inland at Bellanaboy Bridge. From there the main terminal is connected to Ireland’s National Grid The gas is being processed on shore to reduce the risk and danger involved with travelling to and from an offshore platform The Corrib Gas field is estimated to have approximately 80% of the Kinsale gas fields and thus provides a great opportunity for Ireland’s economy The extraction of natural gas at Corrib gas field are expected to boost Ireland’s Gross Domestic Product by over €3 billion and will create over 800 jobs with 150 high-quality permanent jobs which will lead to a decrease in outward migration of the west of Ireland The natural gas reserves at Corrib will provide up to 60% of Ireland’s annual gas requirements for the next fifteen years The availability of natural gas in the west of Ireland has made the west a more attractive place for investment and relocation of industry which in turn has provided more job opportunities and funding for local community investments More than 600,000 households have been connected to the pipeline network which leads to a decrease in our dependence on imported fossil fuels which helps Ireland’s Balance of Payments and keeps more money inside our economy Due to the Corrib gas plant the infrastructure of road and rail has improved greatly which has led to a higher standard of living for people living in the north west of Ireland There are some disadvantages of the Corrib gas field as carbon dioxide is released into the atmosphere during the extraction of the gas and it is believed W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 10  Core Unit 1: Physical Geography it could increase Ireland’s greenhouse gas emissions to the atmosphere by 11% annually There are concerns still over the safety of the plant both the location of the on-shore production plant and the route and depth of the pipeline in North Mayo Due to the finding of the Corrib gas field there has been lots of continued exploration for oil and natural gas reserves and there has been an increased demand for the licences Past Exam Paper Questions Click here for all Past Paper Questions & Marking Schemes broken down into specific topics. W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 11  Core Unit 1: Physical Geography Explain the formation of sedimentary rocks – 30 marks 1. Example – Limestone 2. Example – Sandstone 3. Sedimentary rocks are formed when sediments at the bottom of the sea are compressions, compacted and cemented together naturally. Sediments include tiny rock fragments, sand, clay, plant and animal remains 4. The sediments are compressed together by the weight of the overlying sediments. The process of compaction and cementation is known as lithification 5. Sedimentary rocks are usually laid in strata with defined bedding planes between the strata. These series of layers are known as stratification 6. There are three groups of sedimentary rocks – organic, inorganic and chemical. Organically formed sedimentary rocks are the compacted remains of plant and animals e.g. Limestone 7. Inorganically formed sedimentary rocks are the compacted remains of pre-existing rock fragments e.g. sandstone 8. The top layers of the sand compresses the lower layers, so it is well solidified, and the different strata are separated by bedding planes. Through lithification it transfers from sand to sandstone. 9. Chemically formed sedimentary rocks are formed when water is evaporated from sea area and the sediments are compacted together by the weight of mud and sand into stratified rocks e.g. gypsum which can be found in Co. Cavan 10. Rock salt is used to grit roads and gypsum is used in the manufacturing of cement and plaster boards. 11. Limestone is an organic sedimentary rock. Limestone is a sedimentary rock that has joints and bedding planes. Joints are vertical lines of weakness throughout limestone that were formed when the rock was compressed by plate movements. 12. Bedding planes are the horizontal cracks between layers of sedimentary rock. Water can move easily through limestone, down through the joints and along the bedding planes and down through the joints again 13. Limestone is slowly and chemically weathered by rainwater in a process called carbonation. As rain falls through the atmosphere and soaks through soil, it absorbs carbon dioxide to become a weak carbonic acid. This weak acid slowly dissolves limestone. This process is very evident in karst areas e.g. the Burren, Co Clare, where limestone rock has been exposed. 14. The Irish limestone was form over 300 million years ago and the limestone is usually grey in colour and limestone is used in cement. 15. Diagram W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 12  Core Unit 1: Physical Geography Explain the formation of metamorphic rocks – 30 marks 1. Example – Limestone changed to Marble 2. Example – Shale changed to Slate 3. Metamorphic rocks were once igneous or sedimentary rocks. They were changed both physically and chemically by great heat and/or pressure 4. If the rocks were changed because of great heat this is known as thermal metamorphism and this happens when heat from volcanic eruptions changes the rocks it comes into contact with 5. If rocks were changed because of great heat and/or pressure this is known as regional metamorphism and this happens at destructive plate boundaries e.g. during the Caledonian folding period 6. The process of change from an older rock into a new and different rock is called metamorphism. When metamorphism takes place new minerals may form, the rock texture changes, old minerals will change shape, size and arrangement which is known as recrystallisation 7. The colour of rocks may change too due to the chemical reaction that takes place to the existing minerals in the rock. An older rock that exists before metamorphism is known as protolith. 8. There are three types of metamorphism 1) Thermal metamorphism, Regional metamorphism and Dynamic metamorphism 9. Thermal metamorphism occurs at temperatures between 250-850 degrees Celsius. Magma pushing into the Earth’s crust heats up the rock. This heated contact zone around a magma intrusion is known as an aureole. 10. Marble is formed due to the thermal metamorphism of limestone at destructive plate boundaries. When the plates collide, limestone is subducted and on entering the mantle it melts forming magma. The magma then rises cooling the surrounding limestone changing it into marble. Marble comes in different colours - the green marble of Connemara or the white marble of Rathlin Island, Co. Donegal. 11. Dynamic metamorphism occurs at destructive plate boundaries when pieces of crust slip past each other in opposite directions. It is metamorphism resulting from deformation. 12. Gneiss is formed from another metamorphic rock, schist. The schist formed from fine grained sedimentary rock, shale and can also be formed from granite. It is formed due to great pressure which is regional metamorphism caused as a result of moving plates at destructive plate boundaries. 13. Slate forms due to the dynamic metamorphism of shale. At destructive plate boundaries shale is put under immense pressure. This pressure compresses the shale into different layers or strata, forming slate. 14. Slate is waterproof and it splits easily into thin sheets making it ideal for roofing but trade in slate has declined due to the greater use of tiles. Slate is found in Kilaloe, Co. Clare 15. Diagram W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 13  Core Unit 1: Physical Geography Explain the formation of Igneous rocks – 30 marks 1. Example – Granite 2. Example – Basalt 3. Igneous rocks are formed from the cooling of very hot molten magma above or below the Earth’s crust 4. Magma is pushed up through the crust from the asthenosphere. Magma rises up because it is less dense than crustal rocks. Also, it rises up as it is squeezed due to the pressure of the overlying rocks 5. Magma has temperatures of over 1200 degrees Celsius and therefore melts some of the crustal rock as it rises upwards 6. Igneous rocks are mainly found at destructive & constructive plate boundaries as the magma is able to escape up through the faults & fissures 7. Magma/lave cools once it is exposed to the cooler temperatures and crystallisation will take place. The speed of cooling will influence the size of the crystals within a rock i.e. if it cools quickly the crystals will be small e.g. granite and if they cool slowly the crystals will be large e.g. granite 8. Igneous rocks can be intrusive (plutonic) or extrusive, depending on where the magma/lava cools. If the magma cools beneath the Earth’s crust that they’re known as intrusive rocks and if they cool above the Earth’s surface they’re known as extrusive rocks. 9. Granite is an intrusive rock and basalt is an extrusive rock. Granite is an intrusive igneous rock formed when magma cools slowly under the earth’s surface. Granite has a different chemical composition to basalt. 10. Granite is a plutonic (intrusive) rock that is formed at convergent plate boundaries. The magma cools and hardens underground. However, it is found at the surface when the overlying material has been removed by weathering and erosion. 11. Granite is composed of three minerals: mica, feldspar and quartz. The proportions of these minerals vary creating granites of many different colours and textures. However, grey is the dominant colour found in Ireland 12. An example of where Granite is found in the Leinster Batholith, formed 400 million year ago during the Caledonian folding movement. Magma chambers formed under the surface where the magma slowly cooled to form granite. Nearby rocks were baked and cooked by the intense heat into metamorphic rocks, e.g. sandstone was metamorphosed into quartz. 13. Basalt is an extrusive igneous rock formed when lava cools quickly on the surface. Lava escapes through fissures and volcanoes and is cooled quickly by air and water. Thus, basalt is smoother with tiny crystals and a glassy texture and is known as an obsidian rock 14. The Giant’s Causeway’s hexagonal columns of basalt are a world-renowned tourist attraction. At the Giant’s Causeway, lava cooled quickly in a stream where the water caused the basalt to shrink and contract into the famous hexagonal columns 15. Diagram W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 14  Core Unit 1: Physical Geography Explain how humans interact with the rock cycle – 30 marks 1. Geothermal energy is energy that is extracted through natural heat from the Earth’s core - Example Iceland 2. Geothermal comes from the Greek words geo which means earth and therme which means heat. Several countries, especially Iceland and New Zealand, use geothermal energy. 32% of Iceland’s electricity comes from Geothermal energy. 3. Iceland’s position on the mid-Atlantic ridge allows it to use geothermal energy to make electricity and to heat water. Iceland has five geothermal power plants and geothermal heating provides hot water for 98% of Iceland’s housing. It is such a cheap source of heat that some footpaths of Iceland’s capital (Reykjavik) are heated 4. Geothermal energy uses the rock cycle to provide heat and power. Magma in the mantle pushes its way into fissures in the crust of the Earth and has temperatures of over 1200 degrees Celsius and therefore the magma increases the temperature of the rocks near the crust. Magma near the Earth’s surface superheats water above its boiling point, often reaching temperatures of over 200 degrees Celsius. Temperatures of crustal rocks naturally increases with depth by about 25 degrees Celsius per kilometre 5. Technology has helped to extract the geothermal energy as the Earth’s Crust is drilled from the surface. The hot water/steam can be pumped up through pipes from underground hot water reservoirs. If there is a shortage of ground water cold water is pumped into a rock via a series of wells. 6. The steam from the heated water is used to turn turbines within a generator which in turns creates electricity. As the steam cools, it condense back into water & is injected back underground to be used again and the cycle is repeated 7. Geothermal energy has reduced the need for fossil fuels and helped reduce harmful greenhouse gas emissions. The hot water can be distributed directly to homes and industries to supply hot water and central heating. It is also used to heat greenhouses for vegetable production. In this way Iceland can produce salad crops cheaply and reduce expensive imports 8. 85% of all Iceland’s home use geothermal energy as a heat source which allows for low home-heating costs & stops prices of home-heating fluctuating as they aren’t relying on fossil fuel import. 9. Geothermal energy is 80% cheaper than the electricity generated from fossil fuels and its significantly better for the environment as it is a sustainable source of energy with very low CO2 emission levels compared to burning fossil fuels which could help to reduce the dangers of climate change 10. In Iceland geothermal energy is also a tourist attraction. One power plant just south of Reykjavik uses mineral rich water from the power station to fill up a nearby lake known as the Blue Lagoon. This has become one of Iceland’s most famous tourist destinations and has a spa complex beside the lagoon where the water is kept at 40 degree Celsius for bathers 11. Other effects of geothermal energy are geysers (a spouting spring erupts boiling water and steam every five minutes or so) and geothermal springs which are tourist attractions in Iceland. The Geyser area is one of Iceland’s most famous tourist destinations due to the geothermal activity that occurs here. It has several hot bubbling mudpools and geysers which attract thousands of tourists to the area each year 12. Employment is another huge advantage of using geothermal energy as it has created direct and in- direct employment for people in Iceland. 13. There are some disadvantages of geothermal energy however as there are high installation costs involved as the equipment and technology use is very specialised e.g. underground pipes. The extraction of too much water from the ground may lead to subsidence of the overlying ground surface 14. The are some environmental concerns too as the extraction of geothermal energy leads to the emissions of sulphur dioxide which in turns pollutes our water system 15. Diagram W: www.examrevision.ie | T- @examrevision4u | © ExamRevision 2020 15