Edexcel Geography A level Tectonics

Edexcel Geography A Level Tectonics-Free PDF

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Why are some locations more at risk from tectonic hazards. The Global Distribution of Hazards, A hazard is a potential threat to human life and property. A natural hazard can be either hydro meteorological caused by climatic processes or. geophysical caused by land processes, Geophysical hazards occur near plate boundaries These plates move at different speeds. and directions which can cause collisions earthquakes and volcanic activity as shown in the. Earthquakes can also occur near the middle of plates called intra plate The causes of this. are not fully understood but it is assumed that plates have pre existing weaknesses which. become reactivated forming seismic waves For example an intraplate earthquake may. occur if solid crust which has weakened over time cracks under pressure. Volcanic hotspots such as the Ring of Fire are also situated amongst the centre of pates. This is a localised area of the lithosphere Earth s crust and upper mantle which has an. unusually high temperature due to the upwelling of hot molten material from the core. At hotspots such as the Hawaii hotspot magma rises as plume hot rock. Plate Tectonics and Theories, The Earth s structure as shown in the picture is divided. into four sections crust mantle outer core inner core The. crust is divided into a series of plates These plates are either. oceanic thin and dense or continental thick,Radioactive reactions occur inside the core which. produces convection currents in the mantle This causes the. tectonic plates to move, At mid ocean ridges there is a push and slab pull This is.
the process of subduction where oceanic plates are pushed. www pmt education, under continental as oceanic plates are heavier The Pacific Plate is one such example. which has a lot of subduction around its edges, Plate Tectonic Theory is believed to be correct due to evidence from Wegner s Continental. Drift Theory which states that the shapes of South America and Africa seem to fit together. so were once part of a supercontinent As plates moved the continent separated This is. further verified by similar fossils found were these plates could have fit but are now. separated by oceans, Another piece of evidence is studying how seismic waves travel through the Earth Along. the Wadati Benioff foci the depth of waves shows subduction of the denser basaltic. oceanic plates into the upper mantle, Sea Floor Spreading occurs when two oceanic plates move away from each other allowing. magma from the mantle to rise and form new crust ridges within the ocean resulting in the. sea floor widening, When the magnetic patterns of cooled magma palaeomagnetism were studied it was.
discovered that the magnetic patterns were arranged in the direction of the earth s magnetic. field which switch every millions of years This helps identify the age of the oceanic crust by. studying the youngest rocks at ridges and proves that the earth did once fit together. Plate Boundaries,www pmt education,Destructive plate boundaries. Continental and oceanic,Denser oceanic plate subducts below. the continental,The plate subducting leaves a deep. ocean trench,Built up pressure from the melting,plate cause explosive volcanoes. bursting through the continental plate,Oceanic and oceanic.
Heavier plate subducts leaving an,ocean trench,Built up pressure causes underwater. volcanoes bursting through oceanic,Lava cools and creates new land called. island arcs,Continental and continental,Both plates are not as dense as oceanic. so lots of pressure builds,Ancient oceanic crust is subducted. slightly but there is no subduction of,continental crust.
Pile up of continental crust on top of,lithosphere due to pressure between. Fold mountains formed from piles of,continental crust. Constructive plate boundaries,Oceanic and oceanic,Magma rises in between the gap left by. the two plates separating forming,new land when it cools. Less explosive underwater volcanoes,formed as magma rises.
New land forming on the ocean floor by,lava filling the gaps is known as sea. floor spreading as the floor spreads,and gets wider. www pmt education,Continental to continental,Any land in the middle of the separation. is forced apart causing a rift valley,Volcanoes form where the magma. Eventually the gap will most likely fill,with water and separate completely.
from the main island,There are further forces influencing how. convergent boundaries occur,Ridge push,The slope created when plates move apart has. gravity acting upon it as it is at a higher,elevation Gravity pushes the plates further. away widening the gap as this movement is,influenced by gravity it is known as. gravitational sliding,When a plate subducts the plate sinking into.
the mantle pulls the rest of the plate slab,with it causing further subduction. Conservative plate boundary,Between any crust the parallel plates move in. different directions or at different speeds,No plates are destroyed so no landforms are. www pmt education,Geophysical Primary Hazards,Earthquakes. The most powerful earthquakes occur at destructive and conservative. boundaries, At constructive boundaries Plates move at different speeds which builds pressure.
until plates crack causing fault lines This results in the release of energy in the. form of seismic waves producing earthquakes, At destructive one plate is forced under the other getting stuck due to friction. which produces energy As plates suddenly jerk past one another this energy is. quickly released as large seismic waves forming a powerful earthquake. At a conservative boundary plates lock with one another which when pressure is. built produces sudden seismic waves, Seismic waves can be split into categories Primary Waves cause the immediate. shock whilst Secondary Waves has a longer wavelength and arrives seconds. later Love Waves only travel through the crust causing horizontal movement. Finally Rayleigh Waves will displace the land both vertically and horizontally due. to the compressions caused in the rolling Earth s crust. These waves can also result in crustal fracturing producing faults and. secondary hazards such as landslides avalanches and liquefaction. Tsunamis are produced by sub marine earthquakes at subduction zones causing. water displacement and deep trough waves, This hazard is always secondary to earthquakes adding to death tolls Tsunamis. present additional damage to vulnerable communities such as accelerating coastal. erosion which is a case in Malibu Santa Monica in California. The movement of plates under the ocean causes an uplift of ocean water. disrupting the sea bed,Volcanic Hazards, The world s active volcanoes are found at constructive and destructive plate. boundaries and at hotspots These volcanoes eject magma gases ash and dust. At constructive margins magma is less dense than the plate so rises above it. forming a volcano such as those within the Rift Valleys. At destructive margins subduction causes the melting of the oceanic plate. allowing for magma to rise on the crust to form a volcano This produces explosive. volcanoes such as Mt St Helens in the Ring of Fire. The shape of a volcano determines its destructive ability A super volcano is the. most destructive but seldom occurs A composite cone is said to be more. dangerous than a shield volcano, Volcanic hazards involve lava flows and phreatic eruptions Away from the.
volcano the greatest threats are pyroclastic flows which carry heated rock and. ash over larger distances, Secondary hazards involve water in the form of lahars mudflows and. jokulhlaups glacial floods,www pmt education,Hazards Disasters and Vulnerability. In 2000 700 million were affected by 170 reported, A disaster is when a hazard affects human wellbeing. Degg s Disaster Model suggests a disaster only,happens when a hazardous event meets a vulnerable. population, Vulnerability i s how susceptible a population is to damage caused by a hazard Resilience.
is how well a population can recover from a disaster. A risk i s the likelihood of humans being affected by a hazard It is determined by the risk. Hazard x V ulnerability,Risk Capacity T o Cope, The disaster risk equation helps explain why similar hazards cause disasters of different. degrees For instance both Izmit Turkey and Kashmir Pakistan had a similar sized. earthquake in 1999 and 2005 respectively However Kashmir had 75000 deaths whilst Izmit. had 18000 This was because Kashmir is situated in a remote mountainous location with. poor access to services infrastructure which hinder capacity to cope. Thus impacts of disasters vary according to the levels of development For richer. countries there are high financial losses whilst poorer countries are left with severe shocks. to community wellbeing and infrastructure The poor are also vulnerable to secondary. hazards such as diseases which may arise from the inability to receive international aid. For the emerging world such as India and China disasters can slow growth and potentially. destroy economic systems, The Pressure and Release model PAR proposes what should be tackled if the risk of a. disaster is to be reduced, Vulnerability greatly influences the level of risk in the Pressure Release Model There are. five types of vulnerability, o Economic Vulnerability People risk losing jobs assets or money. o Environmental Vulnerability Location is at a higher risk than others due to. population pressures, o Social Vulnerability A household or community are unable to support the.
disadvantaged within leaving them at risk to hazards. o Knowledge Vulnerability People lack education training or warning of a hazard. o Physical Vulnerability Living in a hazard prone area with buildings offering little. protection,www pmt education,Measuring and Comparing Tectonic Hazards. Tectonic disasters can be measured using different scales The magnitude of an earthquake. can be measured using the Richter Scale uses the arrival times of the primary and. secondary waves and the Moment Magnitude Scale which being more accurate uses the. energy released and the movement produced by shockwaves to calculate magnitude Both. these scales are logarithmic each level is ten times greater than the one before. The intensity of an earthquake can be measured using the Mercalli Scale which takes into. account damage produced, Volcanic eruptions can be monitored using the Volcanic Explosivity Index VEI which. uses the amount of energy released and the type of eruption to calculate a value This scale. is also logarithmic, Earthquakes volcanoes and tsunamis have different characteristics in terms of magnitude. speed of onset duration frequency and spatial probability These characteristics can be. used to compare different hazards using a Hazard Profile shown below. Each disaster also varies in its destructive capacity Impacts can be either social. economic or environmental as well as being direct indirect primary secondary and. long term short term, Generally the less developed a country the more likely it is to face more severe impacts of. a tectonic hazard,Development and Governance of a Disaster.
People remain vulnerable to disaster risks due to inequality in access to education housing. healthcare and a reliable income All of these provide safety nets in the case of a disaster. Additionally pressures such as large urbanisation rates and population growth cause. more people to be vulnerable to risks Increasing world poverty and the exploitation of. resources creates vulnerability and a shattered resilience for the poor. The World Risk Report produced in 2014 commented that urban governments of rapidly. growing megacities such as Mumbai face the major challenge of establishing planning. measures to reduce vulnerability, Japan s government have focused policies in disaster preparedness to reduce vulnerability. and increase the capacity to cope For instance the Disaster Preparedness Day held. annually on 1st September prepares communities for evacuation and educates them in. mitigating against social or economic loss,www pmt education. For countries which are more economically developed there is adequate public. infrastructure housing food supplies and healthcare which although not equally distributed. lowers the impact of a disaster, Corruption government poor warning systems and weak community strength will. exacerbate a hazard into a disaster The government and their actions are perhaps at the. pinnacle of causing or mitigating a disaster,Management and Mitigation of Tectonic Hazards. Tectonic Disaster Trends and Patterns, At a global scale deaths have decreased whilst economic losses have risen This is.
because the global economy and wealth has increased. The increased use of international aid and preparedness also means that less people are. affected by disasters now than in 1960 However data is based on estimates only the exact. number of deaths is often unknown It,is thus important to consider the. accuracy of data presented,The number of tectonic disasters have. fluctuated having peaked in 1997 and,2000 and reaching an all time low in. the early 1980s and 2012,It is incredibly difficult to predict. tectonic hazards such as earthquakes, as they occur without warning Volcanoes can be monitored for changes in shape small.
Edexcel Geography A level Tectonics Essential Notes www pmt education Why are some locations more at risk from tectonic hazards The Global Distribution of Hazards A hazard is a potential threat to human life and property A natural hazard can be either hydro meteorological caused by climatic processes or geophysical caused by land processes Geophysical hazards occur near plate

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