Geography S3 PDF

Tectonic Topic Geography for S3, brief notes and overview Tectonics Topic 1 Tectonic Plates 1.1 What is the plate tectonic theory? a. What is the plate tectonic theory? The theory of plate tectonics is a scientific theory that explains how the Earth's outer she...

Tectonic Topic Geography for S3, brief notes and overview Tectonics Topic 1 Tectonic Plates 1.1 What is the plate tectonic theory? a. What is the plate tectonic theory? The theory of plate tectonics is a scientific theory that explains how the Earth's outer shell is broken into large plates that move and interact, creating major landforms and geological events This explains how the theory leads to Earth has 3 layered structure Earth’s lithosphere is broken up into tectonic plates Tectonic plates are constantly moving Plate movements result in the formation of major landforms (mountains, volcanoes, oceanic trenches) and also explain earthquakes and tsunamis The internal structure of the earth Core ○ Innermost layer ○ Hottest layer 4400-6000℃ ○ Thickest 3300km Mantle ○ 2900km thick ○ Hot 1000-3700℃ Crust ○ Outermost layer ○ Thinnest 6-70km Types of plate boundaries 1  Divergent plate boundaries (move away) Convergent plate boundaries (move toward) Transform plate boundaries (slide past) b. What are convection currents and slab-pull force? How do convection currents lead to tectonic plate movement Heat is generated in the core Heat causes mantle material to become less dense and rise Mantle spreads beneath the plate and drags tectonic plates away from each other, creating a divergent boundary Mantle material loses heat and sinks towards the core The sinking of cold mantle drags tectonic plates towards each other, creating convergent boundaries Mantle material heats up again, process repeat How does slab-pull force lead to tectonic plate movement Only observed at convergent plate boundaries where subduction occurs Plates move toward each other Gravity acts upon the subducting plate, causing it to sink deeper under its own 2  weight 1.2 How does sea floor spreading support plate tectonic theory a. What is seafloor spreading? Seafloor spreading is a process that occurs at mid-oceanic ridges where two plates are moving away from each other. Magma from deep within the Earth then rises through mid-ocean ridges, cools and solidifies, constructing new oceanic crust b. How does the evidence of seafloor spreading support the theory of plate tectonics? Rocks near the centre of the mid-ocean Sediment accumulation in oceanic ridge trenches They are younger. Lesser accumulation. Magma rises from the mantle When the new oceanic crust is cools, and solidifies, to form a new formed, it will not have existed sea floor long enough for much sentiment This will push the older seafloor to accumulate further from the mid-oceanic ridge 1.3 How does magnetic striping support plate tectonic theory a. What is magnetic striping? 3  occurs due to the normal and reversed polarity of Earth's magnetic fields, which leads to stripes of rock on the seafloor with alternating magnetic properties b. How does the evidence of magnetic striping support the plate tectonics theory? Basalt, a volcanic rock that forms the oceanic crust, Contains minerals that can be influenced by Earth’s magnetic field, recording the magnetic field of Earth at that time 1.4 What will happen to different tectonic plates when they move at the different plate boundaries? a. What are the different types of plate boundaries? 4  Type of plate boundary Example Divergent plate Oceanic-Oceanic divergent plate North American Plate and boundary boundary Eurasian Plate Continental-continental divergent plate Within the continent of boundary Africa Type of plate boundary Example Convergent Oceanic-oceanic convergent plate Philippine Plate and the plate boundary boundary Pacific Plate Continental-continental convergent Eurasian Plate and the plate boundary Indian Plate Oceanic-continental convergent plate Australian Plate and boundary Eurasian Plate Type of plate boundary Example Transform NIL The Pacific Plate and the plate boundary North American Plate NIL The Scotia Plate and the Antarctic Plate b. What happens to tectonic plates at divergent plate boundaries? What happens at divergent plate boundaries? mid-oceanic ridges volcanoes (including submarine volcanoes and volcanic islands) rift systems earthquakes. 5 Oceanic-Oceanic divergent plate Continental-continental divergent plate boundaries boundaries Volcano and earthquake ✅ Volcano and earthquake ✅ When 2 plates move apart, When two continental plates move decrease in overlying pressure, apart, the rock fractures and forms causing parts of the underlying parallel faults. mantle to melt forming magma The rock between these faults Magma rises through weak areas collapses to form a deep rift valley in the crust with steep sides. These rift valleys are areas where mid-oceanic ridges earthquakes occur as stress and Lava cools and solidifies to make up new tension are released when plates move. oceanic crust As the plates move apart, the volcanoes decrease in overlying pressure Magma rises through cracks from causes parts of the underlying mantle to melt, forming magma. submarine volcanoes Magma rises through weak areas rift systems in the crust to the Earth’s surface, The Centre of the ridge is riff Valley forming volcanoes. Earthquakes. Stress when plates move c. What happens to tectonic plates at convergent plate boundaries? What happens at convergent plate boundaries? fold mountains volcanoes (including submarine volcanoes) oceanic trenches Earthquakes Oceanic-oceanic Continental-continental Oceanic-continental convergent plate convergent plate convergent plate boundaries boundaries boundaries Volcano ✅ Earthquake ✅ 6  Volcano ❌ 2 plates move Subduction does 2 plates move toward each other not occur as toward each other Two oceanic plates continental plates The denser oceanic collide, and the are too buoyant plate subducts denser of the two Instead, when the beneath the plates sinks two plates collide, continental plate beneath the other the enormous forms an oceanic plate. (subducts) pressure causes the trench in the oceanic trench in rocks on the plates subduction zone the subduction to be uplifted and As the subducting zone. buckled to form fold plate sinks into the As the subducting mountains. mantle, the plate sinks into the Earthquakes are high-pressure mantle, the very common here forces water out of high-pressure and can be violent its oceanic crust. forces water out of due to the Water lowers the its oceanic crust. enormous build-up melting point of the Water lowers the of pressure. Here, overlying mantle, melting point of the magma does not causing it to melt, overlying mantle, rise to the surface, forming magma. causing it to melt, hence no volcanoes Magma rises forming magma. are formed. through weak areas Magma from the in the crust to the asthenosphere rises Earth’s surface, to reach the Earth’s forming volcanoes surface, forming a on the continental crescent chain of plate. volcanoes (which Friction along the remain underwater subducting oceanic and are known as plate causes submarine earthquakes to volcanoes, while occur. some rise above the The enormous sea level as pressure at this volcanic islands.) plate boundary causes the rocks on the continental plate to be uplifted and buckled, leading to the formation of fold mountains. 7  d. What happens to tectonic plates at transform plate boundaries? At transform boundaries, two plates slide horizontally alongside each other, and no crust is created or destroyed. However, the stress caused by the plate movement produces a fault, which is a zone of fractures between two blocks of rocks. Earthquakes occur here as one block of rock suddenly slips past another. However, as magma does not rise to the Earth’s surface, there are no volcanoes at transform plate boundaries. 8 Tectonics Topic 2 Volcanoes and Earthquakes A. How do tectonic processes affect the magnitude of earthquakes? a. How do tectonic processes result in earthquakes? Plate boundaries contain systems of deep fractures in the Earth’s crust, called faults. Fractures in the Earth's crust where there has been movement. Most earthquakes occur along these faults. Along a fault, when rock masses on either side of the fault are pushed by tectonic forces, friction causes them to get locked. This causes stress to build up. When the stress exceeds the strength of the fault (or rock), the rocks snap or suddenly move to a new position. The energy released during an earthquake. Seismic waves are then released, causing ground shaking. In general, the shaking is felt more strongly at the epicentre and becomes weaker as they travel further away. Hence, often, the closer a place is to the epicentre of the earthquake, the more severe the damage caused. 9  How does an earthquake occur in a subduction zone? As one plate subducts under another, the plates may get stuck due to friction. This is followed by the build-up of pressure on the rocks, When the stress exceeds the friction between the plates, they snap to a new position. Finally, mention how seismic waves are released resulting in an earthquake. B. How are earthquakes measured? These seismic waves can be measured using a device called a seismometer Richter Scale (ML) The Richter Scale calculates earthquake magnitude using the height of the largest wave recorded on the seismometer. Thus, earthquake magnitude is measured based on the maximum seismic intensity reached, rather than the total seismic energy released throughout the earthquake. Although not commonly used because it underestimates longer earthquakes 10 The Moment Magnitude 𝑀𝑊 Scale rates earthquake magnitude based on the total energy released during the earthquake. Since it estimates the total energy released during an earthquake instead of just the largest wave like the Richter scale, the 𝑀𝑊 scale is generally more accurate. The 𝑀𝑊scale is especially accurate in measuring earthquakes of magnitude 8 and above. B. How do tectonic processes affect the magnitude of volcanic eruptions a. How do tectonic processes result in earthquakes? crater bowl shape depression at the top of the volcano vent an opening on the earth surface through which volcano erupts There can be a secondary vent if the main one is blocked Located at the bottom of the crater conduit central passageway in the volcano through which magma travels Connects vent to magma chamber 11  magma chamber earth crust where magma is stored vent triangle shape hill or mountain when lava accumulate at vent How do tectonic processes at divergent plate boundaries result in volcanic eruptions? Plates move apart, the crust stretches and cracks develop. The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma. Magma contains dissolved gases and is less dense than the surrounding materials. Therefore, magma rises to the Earth’s surface through weak areas in the Earth’s crust such as fractures to erupt as lava, causing a volcanic eruption. The lava cools, solidifies and accumulates over time, forming a volcano. How do tectonic processes at convergent plate boundaries result in volcanic eruptions? Plates move towards each other. The denser plate subducts under the other. As the subducting plate sinks into the mantle, the high pressure forces water out of its oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma. Magma contains dissolved gases and is less dense than the surrounding materials. Therefore, magma rises to the Earth’s surface through weak areas in the Earth’s crust such as fractures to erupt as lava, causing a volcano eruption. The lava cools, solidifies and accumulates over time, forming a volcano. b. Why are some volcanic eruptions more explosive than others? 12 Stratovolcanoes develop as: 1. High silica magma rises through weak areas in the crust to the Earth’s surface and erupts explosively as lava, ash and rocks. 2. The ash and rocks settle on the sides of the volcano, and are later covered by the lava. 3. Over successive eruptions, a tall volcano consisting of alternating layers of ash and lava develops. 4. As the highly viscous lava travels a shorter distance before cooling and solidifying, the volcano has steep sides and a narrow summit. Shield volcanoes develop as: 1. Low silica magma rises up through weak areas in the Earth’s crust such as fractures to the Earth’s surface and erupts effusively, mainly as fluid lava. 13  2. Over successive eruptions, a volcano consisting of layers of lava develops. 3. As the less viscous lava travels a longer distance before cooling and solidifying, the volcano has gently sloping sides with a broad summit. C. How might distribution of earthquakes and volcanoes influence the spread of tectonic hazards? a. How are earthquakes distributed? Earthquakes may occur away from plate boundaries Occur along convergent, transform, divergent plate Pacific ring of fire Type of plate boundary Example Convergent Pacific Plate moving towards the Philippines Plate Divergent Pacific Plate moving away from the Cocos Plate Transform Pacific Plate sliding against the North American Plate b. How are volcanoes distributed? (Volcanoes are not found along) Transform plate boundaries Continental-continental convergent plate boundaries Hotspots volcano may be located away from plate boundary they can also be located near a plate boundary C. How are are tectonic hazards distributed? 1. are mostly located near plate boundaries, and near earthquakes and volcanoes, while 2. tsunamis and volcanic ash may spread beyond geographic region D. How might tectonic hazards affect natural and human systems? 14  A. What are the hazards associated with earthquakes and how do they affect natural and human environments? hazards include ground shaking, soil liquefaction, landslides and tsunamis Impacts include destroying ecosystems, properties and infrastructure; disrupting services; and causing injury and loss of life destruction of disruption of injuries and affecting natural properties and services (human) fatalities systems infrastructure (human) (human) ground Buildings and Snap and gas trapped Trees uprooted shaking Bridges pipes under - Loss of - Structure - water buildings habitat weakened shortage - Loss of - Collapse Break electricity food trap people and source and - Injury Communication breeding deaths cables ground Railway and - tsunami Roads warnings & - Difficult to television rescue broadcast people affected - Give supply emergency aid soil causes bridges, same same trees on liquified liquefacti roads, buildings soil tip over on to sink in and tip damaged over landslide debris can bury same block rivers farms and floods villages drown people tsunami sweep away same large debris habitat lost i buildings and hit ppl, infrastructure drown Soil liquefaction: Liquefaction occurs when the violent ground shaking causes 15 saturated, loose soil to lose its soil structure and transform into a thick fluid Landslides: Ground shaking causes cracks to form on steep slope, triggers lose rocks and soil to move downwards Tsunamis: 1. An undersea earthquake causes the seabed to be displaced. 2. A large volume of water is lifted, forming a wave of great wavelength and low height of less than 1 metre. 3. The wave travels toward land at high speeds around 800km/h. 4. On approaching the coast, greater friction with the shallower seabed slows the waves down. 5. The waves get closer together and increase in height. Waves can reach up to a height of 15m or more, travel at a speed of 30 - 50km/h and devastate shorelines the waves hit. 6. Before a tsunami occurs, the sea may recede from the shore because the sea water fills in the void caused by the displacement of the seabed. B. What are the hazards associated with volcanic eruptions and how do they affect natural and human environments? 1. hazards include tephra, volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides 2. impacts include destroying ecosystems, properties and infrastructure; disrupting services; and threaten public health and causing injury and loss of life destruction of disruptions of injuries and natural properties and services death systems infrastructure tephra volcanic bombs can fine ash respiratory Fine volcanic damage property and particle might problems, eye ash can ground injure or kill people. damage infections, birds by airplane engine suffocating preventing Ashfall, especially when flight and may wet, can double in blind them as weight, leading to roof ash gums their 16  collapses. Its corrosive eyelids nature weakens together. structures and harms farmland by suffocating crops, devastating livelihoods volcan sulphur dioxide results irritates eye, leads to death acid rain kills ic in acid rain, corrodes skin, nose, vegetation, soil gases buildings throat and kill wildlife lava destroy infrastructure, same as nil destroy forests flow huge areas of earthquake farmlands, forests and other ecosystems pyrocl The hot flows can burn same as burn and kill destroy forest astic through all homes, earthquake people (unable (biodiversity flow properties and to escape) loss) infrastructure in their path. lahars Lahars can bury houses same as not enough pollute river and occupants, block earthquake time to killing wildlife roads, destroy bridges, evacuate and cover farmlands and forests with concrete-like mud. volcan Bury villages and farms, same as earth debris hit or o ic destroying building and quake bury ppl landsli infrastructure des Tephra: Heavier volcanic bombs, with sizes ranging from several centimetres to the size of vehicles, can fall in areas close to the volcano. On the other hand, ash-sized particles may be carried thousands of kilometres by prevailing winds, polluting huge areas of land, including forests, rivers, and farms. Volcanic gases: sulphur dioxide and carbon dioxide 17 Lahars develop when large amounts of ash mix with water, not when molten lava mixes with water Pyroclastic flows are hot clouds of gas, ash, and rocks travelling down the slopes of a volcano. c. What are the benefits of volcanic eruptions and living near volcanoes? 1. volcanic eruption provides fertile soil for farming after volcanic materials are broken down and weathered, and makes available valuable minerals and building materials 2. living near volcanoes allow harnessing of geothermal energy and tourism activities fertile soil for farming Extraction of precious harnessing tourism minerals and fossil fuels geothermal energy Over time, volcanic Magma that cools In Volcanic regions rocks break down beneath volcanoes tectonically attract tourists with through weathering to forms valuable minerals active areas, features like form fertile soils, like copper, gold, and geothermal craters and ideal for agriculture. silver, creating mining energy from activities such as These soils support jobs for locals and the Earth’s hiking. Tourism higher crop yields, income for crust can be creates jobs for attracting farming governments. Revenue harnessed locals as guides communities to from mineral sales can locally to and providers of volcanic areas, where fund social services like provide accommodation, they grow diverse education and cheaper food, and crops and benefit healthcare. Volcanic electricity for souvenirs, boosting economically. materials, such as ash residents. the economy of and sand, are also nearby towns and mined for construction. cities. 18 Tectonics Topic 3 Disaster Risk Management A. How does disaster risk management help achieve sustainable development? What is disaster risk management? 1. prevents, reduces and manages disaster risks thus strengthening resilience 2. involves applying plans and actions which are developed into various strategies by communities Disaster risk management refers to the plans and actions put in place to: ○ Prevent disaster risks before the occurrences of tectonic hazards ​ Disaster risks can have devastating effects, making prevention and mitigation essential. For instance, strategies like hazard-resistant building designs can help structures withstand earthquakes and prevent collapse. ​ ○ Reduce disaster risks during as tectonic hazards occur ​ Strategies to reduce disaster risks include early monitoring and warning systems for earthquakes or tsunamis, allowing timely evacuations and minimizing loss of life. ​ ○ Manage disaster risks after the occurrences of tectonic hazards Post-disaster strategies include facilitating quicker recovery from tectonic 19  hazards through measures like insurance coverage, which provides financial support for rebuilding damaged properties. What is disaster risk and loss? 1. brings serious environment, social and economic consequences 2. is costly for individuals and countries, and may hinder their development Environmental social consequences economical consequences consequences landslides buildings collapse costly to repair or destroying forest (homeless and have rebuild damaged and wet land to live in temporary homes (biodiversity loss) unsanitary homes) Money for Debris from Tsunami leads to education/develop landslide pollute water pollution, ment of river, cause floods spread diseases infrastructure is Volcano eruption Psychological used to repair destroy forest affected which may damaged affect productivity infrastructure Facilities damaged (hospitals and schools) Jobs tourism Why and how do we reduce disaster risks? 1. important for disaster-prone developing countries 2. a cost-effective investment in preventing future losses, thus contributing to sustainable development Reducing disaster risks is more important for disaster-prone less economically developed countries than more economically developed countries B. Why do disaster risks caused by earthquakes and volcanic eruptions 20 vary across places? What are tectonic disaster risks? 1. are the interactions between tectonic hazards, and vulnerability and exposure to earthquakes and volcanic eruptions 2. result in potential loss of human lives and damage to properties Earthquake Volcanic eruption Nature of hazard Duration of Chemical (refers to the nature or earthquake composition of characteristics of these Time of earthquake magma hazards) Vulnerability Building design and Availability of (increase the likelihood of construction surface and ground a community and their Soil and rock water in the properties being affected properties development of by hazards) lahars Prevailing wind conditions affecting direction and distribution of tephra Exposure Population density Presence of human (the extent to which people and assets in settlements and properties are exposed hazard-prone area to tectonic hazard areas.) Distance from epicentre What are the factors influencing disaster risks caused by earthquakes? nature of hazards duration of shaking ○ The longer an earthquake’s ground shaking lasts, the greater the damage it causes. ○ Prolonged shaking increases stress on structures like buildings and bridges, making collapse more likely 21  ○ raising the risk of injuries and fatalities due to trapped victims time of shaking ○ The time of day affects how people respond to an earthquake. ○ At night, when people are asleep, they are less alert and slower to evacuate, increasing the risk of being trapped and injured ○ During the day, people are more alert and can evacuate quickly, reducing the likelihood of injuries and fatalities. vulnerable conditions: quality of building design and construction ○ Usually it’s the collapsing of building that kills ppl ○ Examples, poorly built with low-quality materials such as zinc sheets used in slums ○ lack earthquake-proof reinforcements such as reinforced steel walls ○ Do not follow building codes set by the authorities soil and rock properties ○ Soft, loose soil shakes more intensely than solid rock, ○ increasing the risk of structural collapse and trapping people, which leads to more injuries and fatalities. 22  ○ In contrast, solid rock shakes less, reducing the likelihood of such outcomes. exposure including: population density ○ Higher population density in hazard-prone areas increases exposure to earthquakes, raising disaster risks. ○ In densely populated cities, crowded spaces like apartments, offices, and public transport put many people at risk during an earthquake. distance from epicentre ○ Cities closer to the epicenter experience stronger seismic waves, as less energy is absorbed by the rocks beforehand. ○ This results in more intense shaking, increasing the likelihood of structural collapse and the risk of injuries and fatalities. What are the factors influencing disaster risks caused by volcanic eruptions? 23 nature of hazards: chemical composition of magma ○ The chemical composition of magma determines whether a volcanic eruption will be explosive or effusive (non-explosive). ○ The nature of the eruption influences the associated hazards, thereby affecting the extent of disaster risks. ○ Low silica lava can damage infrastructure and properties over vast areas. ○ High-silica lava produces highly destructive pyroclastic flows, which can cause extensive damage to infrastructure and result in significant injuries and loss of lives. vulnerable conditions including: availability of surface and ground water in the development of lahars, ○ Rapid melting of snow and ice on the volcano’s summit just before or during an eruption ○ Groundwater released through cracks and fractures during a volcanic eruption ○ Heavy rainfall ○ Existing rivers or lakes nearby prevailing wind conditions affecting direction and distribution of ashfall and tephra; and ○ The strength and direction of prevailing wind in particular ○ Prolonged exposure to volcanic ash can lead to respiratory problems as inhaled pollutants irritate the lungs. ○ The heavy accumulation of ash on roofs can cause them to collapse, while ash on farmlands suffocates crops, leading to their destruction. 24 exposure: presence of human settlements ○ Volcanic eruptions in densely populated areas pose high disaster risks due to the greater potential for loss of lives and property damage. ○ In contrast, eruptions underwater, away from human settlements, result in minimal impact. C. How effective are the strategies in building communities’ resilience to earthquakes and volcanic eruptions? 25 Reduce exposure reduce vulnerability increased preparedness land use planning hazard resistant building raise awareness through Controlling and designs education minimising Shock absorber Posters to teach development in high (absorb vibration) people risk areas Diagonal cross How to respond to Decrease potential braces (reinforce natural disasters loss of lives and building) damage to First aid training properties Monitoring and warning Ensure ppl have systems ability to keep Timely warning themselves mobile Allow people to to evacuate react and evacuate timely Evacuation drills Familiarise evacuation routes and procedures 26 Challenges faced in building communities resilience Extend of community’s resources ○ Financially and in terms of technology (land use planning and building designs) Capability of community to organise itself ○ Lack of efforts to educate and train the community to respond and recover from tectonic disasters. ○ Political instability, such as civil unrest. ○ Corruption, which may lead to loss of funding meant to build community preparedness D. How effective are the disaster management strategies after an earthquake or a volcanic eruption? What is disaster management 1. the organisation, planning and application of strategies to 2. respond to and recover from disasters 27 Disaster management refers to how communities can adopt strategies to: Respond to disasters (immediately after the disaster). These strategies include: Search and rescue Timely evacuation Provision of basic social and psychosocial services Recover from disasters (may continue for a long time after the disaster). These include: ○ Restoration and improvement of facilities and living conditions of affected communities. Various groups of people concerned with reducing disaster risks that can affect them directly or indirectly stakeholders need to work together for these strategies to be successful: ○ Local governments are required to assess the damage and to take 28  immediate action such as search and rescue. ○ Non-governmental organisations (NGOs) and private organisations may aid in the provision of necessities and establish relief funds. What are the disaster management strategies? disaster response includes: search and rescue efforts, ○ Using heat sensors and listening devices ○ To save the most number of victims in shortest amount of time time with minimal risk to rescuers Timely evacuation ○ Earthquakes: open spaces ○ Tsunami: to higher ground away from coast ○ Volcanos: away from volcano and danger zone provision of basic social and psychosocial services to affected communities ○ Water: prevent dehydration and water borne diseases ○ Food: crops damaged, emergency food supplies to be given out fairly and efficiently (storage in warehouse, brought from abroad) ○ Health care: availability/access to doctor/medicine ○ Psychological services: which copes with trauma disaster recovery includes: restoring and improving facilities and living conditions of affected communities ○ Hazard resistant buildings What are the challenges in disaster management? 1. lack of domestic resources, including technological and financial resources 2. engaging relevant stakeholders to collaborate and integrate disaster management strategies into their practices (challenges first) ○ Disagreements on matter ○ Underestimating disaster risk ○ High cost 29 30