Geography Knowledge Organisers

Geography Knowledge Organisers

Version 2 Geography Knowledge Organisers Year 9 Summer 2019 Paper 1.Tectonic Hazards 2.Coasts 3.Rivers 1. Tectonic Hazards 1.1 What are Natural Hazards? Natural hazards are physical events such as earthquakes and volcanoes that have the potential to do damage to humans and property. What affects hazard risk? Types of hazards -Population density -HIC/LIC -Location -Time of day -Atmospheric e.g. hurricanes -Geomorphological e.g. flooding on Earths surface -Biological forest fires, living organisms -Tectonics earthquakes, volcanoes, tsunamis 1.4 Earthquakes 1.5 Effects of Tectonic Hazards 1.7 Why do people live near volcanoes? Earthquakes are measured using the Richter scale. Where an earthquake happens is at the focus. The epicentre is the point on the earthquake surface directly above the focus. Seismic waves are released from the focus which are the vibrations you feel during an earthquake Constructive margins usually small, shallow earthquakes as plates pull apart that are usually less violent Destructive margins violent earthquakes as pressure builds and is then released. Found where an oceanic plate and a continental plate push together. Conservative margins plates slide past each other. They catch and then as pressure builds it is released e.g. San Andreas fault. Primary effects happen immediately during the hazard. Secondary effects happen as a result of the primary effects and happen afterwards -Geothermal energy provides electricity and hot water to Reykjavik. -Farming fertile soil used for agriculture. -Mining find valuable minerals on volcanoes -Tourism - Over 100 million people visit volcanic sites per year. Go to see unique views such as the hot springs. Gorkha, Nepal, 2015 (7.9 on the Richter scale). LAquila, Italy, 2009 (6.3 on Richter scale). 1.8 Reducing the risk from a tectonic hazard (earthquake) Primary Effects 1. 2. 3. 4. 5. 1.2 Structure of the Earth The Earth has four layers. The outer layer is called the crust and is made of rock. The layer below is called the mantle and is made of liquid rock. The crust is split into major fragments called tectonic plates. There are 2 types: Continental and Oceanic which is denser (heavier). These plates move and where they meet (plate boundaries) you get tectonic activity (volcanoes and earthquakes). 1.6 Comparing Earthquakes Nepal (LIC) and Italy (HIC) 9000 people died and 20,000 injured (social) Electricity and water supplies, sanitation and communications affect ed. (social/economic) 7000 schools destroyed (social) 50% shops destroyed (economic/social) Damage cost = US$5 billion Nepal (economic) 1. 2. 3. 500 people killed, 12000 injured (social) Significant Chil destruction of e buildings & infrastructure (social/economic ) Overall damage = US$30 billion Secondary Effects There are 2 theories of why plates move: convection currents and ridge push, slab pull. Convection theory: Movement of the liquid rock (magma) in the mantle causes the plate tectonics that are above to move. Ridge push, slab pull: At constructive margins, ocean ridges form beneath them the mantle melts this molten magma rises as the plates move apart. It then cools down to form new plate material. 1. 2. 3. 3 million left homeless Ne Avalanches on mount Everestpal killed 19 people A landslide blocked the Kali Gandaki river, 140km north west of capital Kathmandu causing further flooding 1. Communities cut off by landslides 2. Coastal towns devastated by tsunami. h ile 3. Chemical plant fireC near Santiago forced evacuations. Short term responses (within 2-4 weeks after an earthquake) 1. 2. 3. 4. Search and rescue teams. Tents provided for homeless. Temporary pop-up hospitals Food and bottles water sent 1.

2. 3. 4. Nepa l Swift and effective response by emergency services Key roads repaired within 24 hours Most power and water restored within 10 days US$60 million national appeal built 30,000 emergency wooden shelters Chile Long term responses (months and years after an earthquake) 1. 1.3 Volcanoes 2. 3. Constructive margins Two plates move apart hot magma rises between the plates and cools down to form solid rock e.g. Mid Atlantic Ridge, Iceland. The lava is runny and spreads out and solidifies to form shield volcanoes Destructive margins An oceanic plate subducts (or is pulled down) under a continental plate as it is more dense. At the surface this forms a deep ocean trench. Friction causes oceanic plate to melt and pressure forces magma up to form composite volcanoes (steep sides) eg the Pacific Rim. The lava found at composite volcanoes are sticky. Roads repaired and landslides cleared 7000+ schools rebuilt/repaired Stricter building regulations Nepa l 1. 2. 3. Strong economy reduced need for foreign aid. Government reconstruction plan to help 200,000 households Full recovery within four years Chile Monitoring and prediction -Seismologists use radon detection devices to measure gas that escapes from a volcano before it erupts. -Lasers can be pointed at a volcano to see if it changes shape on the build up to an eruption. -Seismometers can detect small earthquakes or rumbles of a volcano before it erupts Protection -Strengthening roads and bridges to withstand earthquakes provides protection (mitigation). -Earthquake resistant buildings are also used but are expensive. These protect the people but may still be damaged. Example of some of the features of earthquake buildings include rolling weights on the roof that counteract the shockwaves, rubber shock absorbers between foundations, sprinkler systems to extinguish fires, automatic window shutters so glass doesnt fall downwards. Planning -Earthquake survival kit with bottle water, tinned food, extra clothes, a torch, radio, money and sleeping bag if necessary -Planning where evacuation centres would be -On 1st September, Japanese practise earthquake drills as a National training day -American Red Cross provide an earthquake safety check list to help people plan and prepare for earthquakes. 8.4 Coastal Erosion 8. Coasts 8.7 Landforms of deposition Erosion is the wearing away of rock as a result of movement 8.1 Waves Hydraulic action Three factors contribute to the size of waves: 1.The strength of the wind 2.How long the wind blows for 3.The distance in which the wind blows (fetch) Constructive waves: low energy, large swash, small backwash, 6-8 waves per minute Destructive waves: high energy, small swash, large backwash, 10-14 waves per minute The force of water and air into cracks in rocks, causing rocks to break off under pressure Attrition The sandpapering action of pebbles being thrown against a cliff face Pebbles and rocks colliding and grinding against one another to become smoother and rounder Weathering is the breaking up of rocks with no major movement Chemical caused by a chemical reaction when rainwater hits rock and decomposes it Mechanical results in rocks being broken up rather than decomposed Carbonation/acid rain: Rainwater absorbs CO2 from the air and becomes slightly acidic, making an acid called carbonic acid. When it falls this carbonic acid reacts with the calcium carbonate found in limestone. This creates calcium bicarbonate and over time washes and wears the surface of the rocks away. Freeze thaw: Water from rain or waves becomes trapped in a crack or joint in the rock. If the air temperature drops below freezing, the water will freeze and expand by 9-10% putting pressure on the rock. The ice will melt when the temperature rises above freezing. If this process happens repeatedly, the rock will weaken and eventually shatter. Headlands and bay Wave-cut platforms CASS -At discordant coastlines different rock types run at right angles to the coastline -Softer rock is less resistant and erodes further inland -Harder less resistant rock (headlands) erode slower and

stick out -Hydraulic action and abrasion attack the foot of a cliff causing a wave-cut notch -The base leaves the column of rock above unsupported -Overtime the notch is weakened and due to gravity the rock above collapses -As the cliff retreats a wave-cut platform is left -A line of weakness (crack) is widened by hydraulic action in a headland forming a cave -Cave is deepened by abrasion before breaking through to the other side of the headland forming an arch -Arch is weakened at the base by abrasion -Arch collapses due to gravity -Stack remains 8.3 Mass Movement Mass movement is the movement of material downslope under the influence of gravity. It is the falling, sliding or flowing of rock, sediment or soil most often along a slip plane (line of weakness). Landslide Slumping -Longshore drift occurs along a beach -Where a coastline changes shape waves lose energy and there is deposition at the end of the beach -Material is deposited forming a spit -Longshore drift continues and the spit curves because of a secondary wind -A saltmarsh forms behind the spit where water becomes stagnant Sand dunes: At the back of the beach, sand deposited on the beach has been blown inland by onshore winds to form dunes 8.5 Landforms of erosion 8.2 Weathering Rockfall Spits - A spit is a long, narrow finger of sand or shingle jutting out into the sea from the land Abrasion 8.6 Coastal Transportation Longshore drift is the process by which material is transported along a beach Bars: bars are created when a spit extends to another piece of land For a sand dune to form, it needs: -A large flat beach -A large supply of sand -A large tidal range, so there is time for the sand to dry -An onshore wind to move sand to the back of the beach -An obstacle such as driftwood for the dune to form against 8.8 Coastal Management Strategies Hard Engineering expensive man made structures used for coastal protection Strategy Benefits Costs Sea wall concrete wall that reflects wave energy -Very effective at stopping the sea -Walkway or promenade for people to walk along -5000 - 10000 / metre -Very expensive and high maintenance costs Rock Armour large granite boulders at foot of cliff to absorb wave energy -Can provide interest to the coast -Climbing danger for children -2000 000 / 100 metres -Do not fit in with local geology Groynes wooden or stone fences built perpendicular to the beach to stop LSD. -Create wider beaches which can be popular with tourists -Not too expensive -Starve beaches further down the coast making them narrower and so more likely to erode (terminal groyne effect) Soft Engineering natural less expensive methods used for coastal protection -Large boulders of rock fall downwards to form scree at the bottom of the cliff. -Often caused by freeze thaw -When blocks of rock slide rapidly downhill -Occurs in rock that absorbs water it becomes saturated and the weight causes it to collapse down -Rainwater saturated soft rock -Heavy saturated rock causes a curved slip plane -Gravity pulls the slab of soft rock downwards -Waves under-cut further from the base -Prevailing wind pushes the swash up the beach at a 45 angle -Backwash is pulled back into the sea due to gravity at a 90 angle -Process repeats moving material along a beach in a zig-zag pattern Beach nourishment / reprofiling. Adding sand to a beach or changing its shape -Looks natural -Creates amenity for tourism -Cheap and easy to maintain -500 000 /100 metres but can vary -Needs constant maintenance -Less effective than hard engineering Dune Regeneration artificially adding to the size of a sand dune -Considered natural -May increase biodiversity -200-2000 per 100 metres. Time consuming to plant and maintain -Easily damaged by storms Managed Retreat (example: Medmerry) allowing the sea to flood over low - lying land Allow sea to move into area. -Long term solution with low maintenance -A natural buffer

-New ecosystem created -Biodiversity improves, e.g bird watching -Low value land is lost to sea -Local people have to move so need to be compensated -Some ecosystems may be lost 9. Rivers 9.1 River profiles 9.4 Upper course erosional landform: waterfalls and gorges 9.6 Lower course depositional landforms 1.Hard rock overlays soft rock. A waterfall will form where there is a junction between hard rock capping upstream and soft rock downstream. 2.Hydraulic action widens a crack in soft rock to create a plunge pool 3.The plunge pool is deepened into the soft rock by abrasion which undercuts the hard rock and creating an overhang of hard rock 4.The hard rock above becomes unsupported so collapses and retreats upstream 5.The process continues and the waterfall retreats upstream leaving a gorge Levees: When a river bursts its banks heavy sediment is deposited closest to the river creating elongated ridged that extend along a river increasing its capacity. Floodplains wide areas of flat land often good form farming There are two processes responsible for the formation of a floodplain Estuaries Where the river meets the salt water of the sea. Salt marshes are common. 9.7 Boscastle flood 2004: causes Physical Human Precipitation heavy prolonged rainfall days before saturated the ground Geology impermeable rock such as shales and clay = higher risk of flooding as more surface run off Relief steeper slopes = higher risk of flooding as more surface run off Building urban areas: impermeable surface Deforestation :water not stored on trees so increase of water on ground = more surface run off = higher risk of flooding 9.8 Boscastle flood 2004: impacts Social 9.5 Middle course erosional landform: meanders and ox-bow lakes 9.2 Fluvial processes Erosional processes (see coasts 7.4 for hydraulic action, abrasion and attrition) Solution: refers to the dissolving of rocks such as chalk and limestone Vertical erosion: deepening of the river bed by hydraulic action. Evident in the upper course of a river Lateral erosion: sideways erosion, wearing away the banks of the river. Evident in the lower course of a river where it begins to meander Transportation processes Traction: large boulders rolled along the river bed Saltation: smaller rocks bounced along the river bed Suspension: fine light material suspended in the water Solution: dissolved material carried along in the river 9.3 Upper course erosional landform: interlocking spurs -In the upland areas, the geology is composed of hard rock such as granite or slate. Freeze thaw weathering gradually broadens it out. This gives the valley a steep V-shaped cross profile. Repeated weathering weaken the rock so fragments break loose and tumble down the hillside as scree, which the river then removes -The winding path taken by the river is due to obstacles of harder rock in its path. The river takes the easiest route over the land. This results in projections of high land entering the valley from alternate sides. These projections are interlocking spurs 1.Fast flowing water on the outside bank causes lateral erosion through abrasion and hydraulic action, which undercuts the bank and forms a river cliff. (The point of maximum erosion is slightly downstream of the mid point of the loop) 2.Helicoidal flow is a corkscrew movement. The top part of the flow hits the outside bank and erodes it. The flow the corkscrews down to the next inside bend, where it deposits its load as friction slows the flow 3. Fast flow causes erosion on the outside bend. This deepens the river bed, resulting in an asymmetrical cross profile 4.Sand and pebbles are deposited on the inside bank where the current is slower, forming a gentle slip off slope 5.As the meander loop becomes large the neck of land between two meanders becomes increasingly narrow 6.River floods, so main flow of water is cut straight across the neck 7.Continued lateral breaks the neck forming a new straighter channel 8.The old river channel is increasingly detached as it is no longer receiving river water 9. Marsh plants colonise the area. Economic -Cars washed out to sea -Tourists and locals couldnt return to accommodation Environmental -Homes and businesses closed for summer -Less tourism -Oil leaks into sea from cars -Natural ecosystems in river lost in flood 9.9 River Management Strategies Hard Engineering Strategy Benefits Costs Dams & Reservoirs Provides HEP, attracts tourists, very reliable Very expensive, dangerous if it bursts Channel Straightening Increases speed of water to clear, reduces flooding Visually unattractive, expensive to put in place Flood Relief Channels Removes risk of flooding from designated areas Can cause increased flooding downstream Soft Engineering Flood warning and preparation Cheap way of protecting people Only effective if people listen and take action. Flood plain zoning It is low cost only administration costs are involved Difficult to get planning permission to extend or rebuild homes in the floodplain 9.10 Storm Hydrographs Peak rainfall the time when rain is the heaviest Rising limb shows how quickly the discharge rises Peak discharge the highest recorded discharge Lag time the time difference between peak rainfall and peak discharge Base flow- the normal flow of a river

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