Natural Hazard Notes PDF

**[HAZARDS:]** **[The concept of hazards in geographical context:]** **[Nature, forms (written about in greater detail later) and potential impacts of natural hazards (geophysical, atmospheric, and hydrological). ]** Natural hazard = perceived natural event that has potential to threaten life and...

**[HAZARDS:]** **[The concept of hazards in geographical context:]** **[Nature, forms (written about in greater detail later) and potential impacts of natural hazards (geophysical, atmospheric, and hydrological). ]** Natural hazard = perceived natural event that has potential to threaten life and property. 1\. Geophysical = structure failure within crust (lithosphere), driven by the earth's own internal energy sources e.g. plate tectonics, volcanoes, seismic activity. 2\. Atmospheric = energy in the atmosphere, driven by processes in the atmosphere e.g. tropical storm, drought. 3\. Hydrological = driven by water bodies mainly ocean + water e.g. floods, storm surges, tsunamis. Some can be a mixture e.g. tropical storm is a hydrometeorological hazards as it is a mix of hydrological and atmospheric. These impacts can be both primary and secondary. Primary refer to those with an immediate effect on the affected are e.g. destruction of infrastructure and buildings. Secondary impacts happen after the disaster has occurred, such as disease, economic recession and contamination of water supplies. Also impacts depend on the location of the hazard relative to the population. Social Impacts: Loss of life, displacement of communities, injuries, and damage to infrastructure. Economic Impacts: Destruction of property, loss of livelihoods, and costs associated with recovery and reconstruction. Environmental Impacts: Habitat destruction, soil erosion, pollution, and changes in ecosystems. Political Impacts: Government response, policy changes, and international cooperation in disaster management. Biological impacts = diseases + viruses + dangerous wildlife. Disaster = realization of a hazard when it causes significant impact on a vulnerable population. Significant impact = 10 or more killed or 100 or more affected. Hazard = is a potential threat to of substantial loss of life, substantial impact upon life or damage to property can be caused by an event. Hazards can be human (explosions, chemical release into the atmosphere, nuclear incidents) caused or occur naturally (natural hazards e.g. earthquakes, storms, volcanoes and wildfires). Although natural events can be a consequence of human actions e.g. wildfires can be ignited by human carelessness, floods can be brought about by poor land -- use management. An event will only become a hazard when it is a threat to people. E.g. if a hurricane hit an uninhabited desert island it would not be classed as a hazard. A disaster occurs as a result of a hazard, a disaster will only occur when a vulnerable population is exposed to a hazard as seen in Degg's disaster model. Natural hazards and their effects on people tend to have these characteristics: \- Their origins are clear and the effects they produce are distinctive e.g. earthquakes cause buildings to collapse \- Most only have a short warning time before the event \- Exposure to the risk is involuntary -- this is mostly true in LDEs, as HDE people can choose to live elsewhere due to more money \- Most losses to life and damage to property occur shortly after the event although the ffects can be felt in communities long after that time e.g. Cholera 'Loss of property from natural hazards is rising in most regions of the earth and loss of life is continuing or increasing among many of the poor nations' -- written in 1978. Overall, the death rate has fallen more people have been affected by natural hazards than ever. This is due to increasing population and the wide reaching effects of events e.g. earthquake, volcanic eruptions, tropical storms, floods, wildfires and droughts. Risk of disaster: 1. The magnitude/extent/duration of the **Hazard** 2. The **vulnerability** of the people affected 3. The **capacity of a society to cope** **Risk = [hazard x vulnerability]** Risk is the exposure of people to a hazardous event presenting a potential threat to themselves their possessions and the built environment in which they live. Why do people put themselves at risk from hazards: \- Hazard events are unpredictable, cant predict their frequency, magnitude or scale. \- Lack of alternatives: homes, land and employment \- Changing the level of risk: places safety may decrease over time e.g. deforestation increases flooding \- Cost/ Benefit: many hazardous areas offer advantages that outweigh the risk. E.g. California. \- Perception -- written below. [Hazard perception and its economic and cultural determinants:] Characteristic human responses: How we perceive hazards is determined by the effect that it may have on our lives. This increases if people have direct experience of a particular hazard and also how long term the impact of this experience has been. Is only by the presence of people that a natural event becomes a hazard. The pressure of an increasing population and subsequent demand for land has resulted in building an areas that are at increased risk. Population expansion itself can increase the threat of a hazard, for example increasing population at the peripheries of a large urban area may increase the risk of wildfires. The advantages of living with the threat of hazard sometimes outweigh the risk. Making use of fertile soils on flood plains or in the vicinity of a volcano can be considered a risk worth taking and living with the threat is accepted as a part of everyday life. A natural disaster can have catastrophic effects on an economy, not just in the countries that are directly affected but also globally. In the highly developed economies these affects tend to do little long term damage to the economy as there is enough wealth and potential for redevelopment to be able to rebuild infrastructure and support those that are directly affected. Last developed economies are much more reliant on support and aid, both in the immediate aftermath of an event and also in the long term as they try to repair the damage physically socially and economically. Despite living in an area what we perceive as obviously hazardous area, many still underestimate the risk of hazards. In 1971, Rober Kates found that those people who had experiences of storm damage to their property on the East Coast of the USA, most of them did not expect such damage to occur again. Age social status and religious beliefs can be determining factors when it comes to leaving behind in an infatuation all that has been worked for in a lifetime. \- Wealth = the financial situation of a person will affect how they perceive = hazards this is because wealthier people may perceive a hazard to be smaller as their last vulnerable because that house might be bigger. However while there people may also view a risk as greater because they have more property damage and financial loss compared to someone who is less wealthy however this is dependent on the person. \- Experience = someone who has experienced more hazards may be more likely to understand the full facts over hazard but also studies suggesting that people who have experience houses are likely to have an optimistic and unrealistic outlook on future hazards 'lightning never strikes in the same place twice' mentality. \- Education = a more educated person may understand the hazards full effects on people and how devastating they can be and have been in the past. Those who are less educated that may not understand the full extent of a hazard and may not evacuate etc. \- Religion and beliefs = some may view hazards as put there by God for a reason or in being part of the natural cycle of life so they may not see hazards as negative. In contrast those who believe strongly in Environmental Conservation may perceive hazards to be huge risks to the natural environment especially hazards are becoming more frequent due to global warming. Other people might think that hazards must happen for example wildlife fires allow regeneration of forests. \- Mobility = those who have limited access to escape a hazard may perceive hazards to be greater threats than they are. Whether they\'re in a secluded location or if they are impaired with a disability or illness, those who cannot easily leave an area may feel more at risk. Human response: is to reduce life and equity, at a local level this involves saving possessions and safeguarding property; globally this means coordinating rescue and humanitarian aid. The intensity and magnitude of the events as well as the original state of the infrastructure affects the speed of the international response. Response times have been reduced by the development of Automatic Disaster Analysis and Mapping system (ADAM), a database that pools information from the US Geological Survey, World Bank and World Food Programme. This allows almost immediate access to such information e.g. scale of the disaster, supplies that are available locally and local infrastructure. Previously a manual search of several databases took hours, rather than minutes. **[Characteristic human responses -- fatalism, prediction, adjustment/adaptation, mitigation, management, risk sharing -- and their relationship to hazard incidence, intensity, magnitude, distribution and level of development.]** **[Characteristic human responses - fatalism, prediction, adjustment/adaptation, mitigation, management, risk sharing:]** fatalism = 'do nothing' fatalistic approach defeatism, idea disaster will always happen and there is little we can do about it OR will of God, The viewpoint that hazards are uncontrollable natural events, and any losses should be accepted as there is nothing that can be done to stop them, sometimes interfering with processes can have a detrimental effect on ecosystems e.g. wildfires as they are regenerative processes within forest eco system and should be allowed sometimes to take their course. People will do nothing to mitigate against it. adjustment/adaptation = once we accept then natural hazards are inevitable we can adapt behaviour accordingly so losses can be kept on minimum. This is a most realistic option for many people and often proves to be effective and cost effective for governments. Although adaption refers to society adjusting to the hazard it doesn't mean that they aren't completely preventing it. Society are preventing its impacts e.g. building coastal defences (as sea-level is rising) or reducing water usage (as drought is becoming more common). fear = perception of the hazard is such that people feel so vulnerable to an extent that they are nio longer able to face living in the aera and move away to regions perceived to be unaffected by the hazard. prediction = anticipate the hazard, looking to the future. As technology increases the methods of predicting hazardous events become more sophisticated remote sensing and seismic monitoring give clues to activity that may lead to a disaster and need to be acted upon. Advances in communications mean that information from all parts of the world can be shared and analysed quickly. One it can be communicated promptly and reach a greater number of those at risk. This involves using scientific research and past events to deliver warning so impacts of hazards can be reduced and perhaps prevented Mitigation = this refers to strategies which are carried out to lessen the severity of a hazard e.g. sandbags to offset the impacts of flooding. Mitigation can reduce the risk of loss from the occurrence of an undesirable event. Management = co ordinated strategies to reduce a hazards effects. This includes: prediction, adaptation and mitigation. risk sharing = prearranged measures aiming to reduce loss of life and damage through education and awareness programmes, evacuation, emergency medical, food and shelter supplies and insurance e.g. donating money between countries and communities, insurance. A form of community preparedness, whereby the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards. New Zealand is an example of where risk sharing has worked. As a multi-hazard environment, New Zealand is under threat from earthquakes, tsunamis, volcanoes, and weather-related hazards. The cost of these hazards are huge; the Canterbury Earthquake (2010) alone cost the country 20% of it's national GDP. There are now attempts to share the risk by insurance investment, so strategies can be put in place before the disasters rather than investing more in a clean up. Integrated risk management = the process of considering the social, economic and political factors involved in risk analysis; determining the acceptability of damage/ disruption; deciding on the actions to be taking to minimize damage/ disruption. **[Hazard incidence, intensity, magnitude, distribution and level of development:]** - relates to energy in environment. - Hazard incidence = This refers to the occurrence frequency of a hazard and is not affected by the strength of a hazard -- just how often it occurs. Low incidence hazards may be harder to predict and have less management strategies put in place, meaning hazard could be more catastrophic when it does eventually occur. Also, low incidence hazards are usually more intense than high incidence hazards e.g. only 36 recorded earthquakes since 1500 with magnitude of 8.5 or higher but millions are too weak to be recorded. - Intensity = refers to energy/ power of a hazard -- how strong it is and how damaging its [effects and impacts] are. Measured with the Modified Mercalli Intensity scale. Can be dependant on the distance a person is from the hazard. - Magnitude = refers to size and usually this is how a hazards intensity is measured. Usually defined as a number on the Richter scale. High intensity and high magnitude hazards will have worse effects meaning more management requires. So more mitigations strategies will be needed to ensure a relatively normal life can be carried out. - Distribution = this refers to the location of hazards and where they occur geographically. Areas of high hazard distribution are likely to have a lot of management strategies and those living there will be adapted to the hazardous landscape because it dominates the area more so than in places with low hazard distribution. - Level of development = economic development will affect our place can respond to a hazard so if the hazards of the same magnitude may have very different effects in two places or contrasting levels of development. If a hazard is identical in an area with lower level of development it\'s less likely to have an effective mitigation strategy as these are costly therefore the effects of the hazardous event in a LIC and NEE is likely to be much more catastrophic. However there are many high income countries that are not as prepared for natural hazards as they should be meaning they lack the management gestures for an event this is especially true in multi hazard environments where resources are thinly spread over a variety of hazards. For example, in Canada wildfires have been increasing over the last few years however this means that less money and resources have been available for earthquake and tsnuami preparation even detailed evacuation routes and tsunami sirens are not available in popular tourist beaches such as Vancouver Island. Text message systems are available to act as a warning system to suggest people to evacuate for many people switch our phones off at night reducing the effectiveness. Overall level of development may not have the biggest pots playing a hazard and it is more to do with how these countries use their development from mitigation. Community/Resilience = sustained ability of individuals or communities to be able to utilise available resources to respond to, withstand and recover from the effects of natural hazard events, Communities that are resilient are able to minimise the effects of the event, enabling them to return to normal life as soon as possible. Prevention = this is probably unrealistic, there have been new schemes e.g. cloud seeding in potential tropical storms. **[Characteristic human responses -- fatalism, prediction, adjustment/adaptation, mitigation, management, risk sharing -- and their relationship to hazard incidence, intensity, magnitude, distribution and level of development.]** Fatalism would be more prevalent in areas with high hazard incidence, intensity or magnitude. Prediction ability is crucial in area with high hazard incidence and prediction methods will be more effective and advanced in more developed countries. Adjustment/ adaptation are essential in area with high hazard incidence, intensity and magnitude, Mitigation is crucial in areas with high hazard incidence and intensity. Management is needed in critical areas and needs to be effective especially for areas with high hazard incidence to minimise the casualties and facilitate recovery. Developed regions will have more robust management systems. Risk sharing would be essential in areas with high hazard incidence and intensity where potential economic and social impacts can be significant. - Ways chosen to deal with hazards are related to wealth and access to technology. - Humans have a capacity to ignore or seriously underestimate risk, even when seemingly obvious. 1. Do nothing. 2. Move to a safer location. 3. Attempt to prevent hazard. 4. Adapt lifestyle to the hazard. **[Park model of human response to hazards:]** A hazard event causes disruption to everyday life. The type of disruption depends on factors such as the type of hazard, the intensity or magnitude, the immediate environment and infrastructure. The model can be described as 3 phases: relief, rehabilitation and reconstruction.  The Park Model is a graphical representation of human responses to hazards. The model shows the steps carried out in the recovery after a hazard, giving a rough indication of time frame. \- The steepness of the curve shows how quickly an area deteriorates and recovers. \- The depth of the curve shows the scale of the disaster (i.e. lower the curve, lower the quality of life). A diagram of recovery Description automatically generated Stage 1: Relief (hours - days): Immediate local and possible global response -- medical aid, search and rescue and expertise. Immediate appeal for foreign aid -- the beginnings of global response. Stage 2: Rehabilitation (days - weeks): services and infrastructure begin to be restored, temporary shelters and hospitals set up, food and water distributed. Coordinated foreign aid -- peacekeeping forces etc. To allow reconstruction phase to begin as soon as possible. Stage 3: Reconstruction (weeks - years): restoring the area to the same or better quality of life, area back to normal -- eco system restored, crops regrown. Infrastructure rebuilt. Mitigation efforts for future events against the same level of disruption. **e.g. earthquake, tsunami** **e.g. drought or volcano** they would give weeks of warning during which time preparations can be made to mitigate impacts so a less steep curve The model also works as a control line to compare hazards. An extremely catastrophic hazard would have a steeper curve than the average and would have a slower recovery time than the average, for example. This has been indicated by the blue line. A blue and white chart with text Description automatically generated Reasons for and against using Parks Model: For: the model provides A structured framework to allow easy understanding of the different stages of disaster which can help organise complexities of disaster response process. The model can serve as a communication tool. The model can highlight the importance of different actions at various stages. The use of time frames are very effective. Takes into account, quality of life social stability and levels of economic development. Against: A focus on loss only won't improve survival rates when hazard next strikes. Long before a natural hazard event, there needs to be a focus on mitigation and prevention as well as human preparedness. It can be argued that the model over simplifies the complex and dynamic nature of disaster response. The model assumes a linear progression from one place to another which may not be reality the model doesn\'t emphasise importance of community resilience and community building such as mitigation which will strengthen communities to be able to cope with future events. The model may not account for cultural differences and variations in disaster response and its rigid structure may not accommodate the need for flexibility and adaptation. Only takes into account pre disaster and not post disaster. **[Hazard management cycle:]** Preparedness = large scale events can rarely be prevented from happening we thought with education and raising public awareness we can reduce the human causes and adjust behaviour to minimise likely impact of the hazard. Knowing what to do in the immediate aftermath of an event can speed up the recovery process and areas of high risk, the level of preparedness will be greater than in areas where such events are rare. Being ready for an event to occur. Response = the speed of response would depend on the effectiveness of the emergency plan that has been put in place. Immediate response is focused on saving lives and coordinating medical assistance. Damages assessment helps plan for recovery. Immediate action taken after event (evacuation, medical assistance, rescue) Recovery = restoring the affected area to something approaching normality. In the short term this will be restoration of services so that longer term planning and reconstruction to pre event levels can begin. Related to long term responses. Mitigation = Actions aimed at reducing the severity of an event and lessening its impacts. This can involve direct intervention, such as building design that can withstand earthquakes or hurricanes, or preparing barriers or defensible zones that may slow down or even halt the advance of wildfires. Most desirable is a long-term protection of natural barriers such as coral reefs, which protect the shore against storm surges. Support after disaster in the form of aid insurance can reduce the long term impacts. However insurance may not be available at all in high risk areas, even in highly developed economies and is something that may not be available at all in low developed economies which are often those that need it the most. Strategies to lessen effects of another hazard (barriers, warning signals developed, observatories) Reasons for and against using Hazard management cycle: For: The cycle provides A systematic approach to dealing with the natural hazards and ensures all aspects of hazard management are considered and addressed from before the hazard to after the hazard. The cycle emphasises mitigation and preparedness to reduce the impact of any future hazards an enhanced communities resilience for increased organisation of this structure before and after will lead to more efficient and effective emergency response. Also the cyclical structure of this cycle will allow they cycle to be effective for multi hazard environments such as Haiti which is prone to many natural disasters. Against: the hazard management cycle is infers that you can prepare for a hazard however this isn't always true. Developing countries may struggle to allocate resources to all aspects of the cycle. Evaluating the Effectiveness of Models: Hazard models are useful, but the unpredictability of hazards makes the models less effective at accurately representing human responses to hazards. It may be useful to ask some questions when evaluating how effective these models are: \- Can they be applied to every hazard? Are some hazards more complicated and require a more complex model? It may be useful to apply each of your case studies to these models and see how they compare. \- Does the model take any aspects of hazards into account such as level of development? \- Is there any timeframe? Do the models accurately lay out the time taken for a full response and how this changes due to aspects of the hazard such as intensity? \- Could the model be less vague/ include more steps that can be applied to all hazards? \- Does the model present hazards currently? Are there any alterations that could be made to account for hazards affected by climate change? Will the model eventually not represent human responses at the time (e.g. could the cycle stop because hazards will occur more frequently than the mitigation strategies will occur)? Pressure and release model (PAR): how the intersection of unsafe conditions and hazards creates social vulnerability. This is effective because it allows you to see the relationship and causes of social vulnerability. PAR is used to analyze factors which cause a ​population​to be vulnerable to a hazard. On one side of the model we have the ​natural hazard​itself, and on the other side different factors and processes which increase a ​population\'s vulnerability to the hazard.  Disaster risk index (DRI): enables the calculation of the average risk of death per country in large- and medium-scale disasters associated with earthquakes, tropical cyclones and floods, based on data from 1980 to 2000. This is effective as it is easy to read, comparable and simplistic so easy to understand. Shows links too economic development. Risk poverty nexus model:  shows the strong link between poverty and the impacts of a hazard. Those in poverty are the most impacted by disasters and remain in poverty because of the disaster. This is useful as it shows what types of poverty result in impacting hazards and allows future prevention.  Reason's Swiss cheese model: based on an understanding that every step in a process, or every layer of a system, has weaknesses that can lead to failure. This is useful because it can result in prevention of potential weaknesses. Several steps needed. E.g. Every step of a hazard management strategy/ cycle must be followed e.g. Must prepare. **[Plate tectonics:]** **[Earth structure and internal energy sources.]** Over 2000 years ago Plato was considering the structure of the earth. But it wasn\'t until Edmond Halley in 1692 first proposed a theory to describe the earth structure, he suggested it was made-up of hollow spheres rather like the Russian dolls. Halley considered that each spare was actually habitable. Whilst the earth appears to be a perfect spit spare it is in fact a geoid this means it bulges around the equator at his flat at the polls this. The cause of this is centrifugal forces generated by the earth rotation which flings this semi molten interior outwards. **[Crust:]** \- This is the outer layer which we live on, the outermost layer of the lithosphere. \- Varies in thickness from 5 -- 10 km, beneath the oceans to nearly 70km under continents. \- In relation to the earth it is very thin. 2 types of crust: 1\. Oceanic = an occasionally broken layer of basaltic rocks known as sima -- silica and magnesium. Just as oceanic crust is formed at mid-ocean ridges, it is destroyed in subduction zones so it is thinner and younger -- around 6km -- 10km. Less than 200 million years. 2. Continental = bodies of mainly granitic rocks known as sial -- silica and aluminium. Continental crust is rarely destroyed -- around 30km -- 70km. Over 1,500 million years. Oceanic crust is denser than continental crust. Sial = upper layer of the Earth's crust and forms the continental land masses. Sima = lower layer of the earths crust and is found beneath the oceans as well as grading into the lower part of the sial beneath the continents. Sial is much thicker than oceanic sima, but less dense. **[Lithosphere:]** \- Crust and the upper mantle are known as the lithosphere -- a majority is withing the mantle. \- In this zone TP are formed. \- The lithosphere is broken up into pieces. **[The mantle:]** \- The mantle is the widest section of the Earth and is 2900km thick. \- Due to great heat and pressure within this zone, mainly sold rock, rocks are high in silicon - the mainly silicate rocks are in a thick, liquid state which become denser with depth. \- The lower mantle is hotter and denser than the upper mantle and transition zone. \- The rocks in the upper mantle are solid and sit on top of the asthenosphere. The lithosphere rests on the top. \- Aesthenosphere = a layer of softer, almost plastic -- like rock (semi - molten) layer which moves due to flows of heat called convection currents. Movement are powered by heat from the core. It can move very slowly, carrying the lithosphere on top. Densities within the mantle increase as you go down into the lower mantle. **[The core:]** \- The core is the centre and hottest part of the earth where temperatures can reach 5000°. It is mostly made of iron and nickel and is 4 times as dense as the crust. \- The core is actually made-up of two parts. \- The outer core is semi liquid and is mainly iron and some nickel. \- The inner core is solid on is made-up of an iron nickel alloy. It is a solid because of pressure and compression. \- It is thought that as the earth rotates the liquid article spins creating the earth\'s magnetic field. Why is the earth so hot? \- The internal heat is a major cause of the earth\'s tectonic activity. Heat from the earth drives tectonic plates. Some of this heat may be primaeval (retained from the ball of dust and gas from which the earth evolved). But we now know that by far the greatest source of heat energy within the earth is derived directly from radioactivity. Natural radioactive decay of uranium, thorium, potassium and other elements provides A continuous but slowly diminishing heat supply. The earth is in effect, a vast nuclear power station and without this internal energy source the planet would be completely dead and inert. Flows of heat from the earths interior to the surface: \- Radiogenic heat = produced by radioactive decay of isotopes in mantle and crust. Radioactive decay of elements in the earth mantle and crust results in daughter isotopes and release of particles and heat energy or radiogenic heat. \- Primordial heat = left over from the formation of the earth. Primordial heat is heat lost by the earth as it continues too cool from its original formation, in contrast to its still actively produce radiogenic heat. \- The internal heat is transferred from the core through condition into the mantle, here it is moved onwards by convection. \- Earth's heat transport occurs by conduction, mantle convection, and volcanic advection this is where he is carried in molten rock through the crust. \- The earths internal heat flow to the surface is thought to be about 80% due to mantle convection the dominant control on heat transport from deep within the earth. The remaining 20% of heat mostly originates from radiogenic decay in the earth\'s crust and about 1% of this is directly due to volcanic activity earthquake and mountain building. \- 99% of earth\'s internal heat loss at the surface is by conduction through the crust this he is not noticeable at their surface outside of volcanic regions solar radiation is crucial heat input for life on earth \- Convection cells are formed in the earth and this puts pressure on the single plate which fractures and cracks, Convection cells are areas within a fluid where warm material is rising in the center and cold material is sinking. In the atmosphere, these cells can occur at small scales (like a sea breeze at the beach) or much larger scales. The heat at the core generates convection currents within the mantle above. These currents spread very slowly within the asthenosphere -- they are important but not solely responsible for the movement of TP.  Magma = molten rock, gases and liquids from the mantle accumulating in vast chambers at great pressures deep within the lithosphere. On reaching the ground surface magma is known as lava. Igneous rocks = rocks formed by cooling of molten magma either underground (intrusive) or on the ground surface (extrusive). Intrusive = magma cools, crystallised and solidifies slowly below the surface is intrusive. It forms coarse grained igneous rocks e.g. granite and dolerite. Vertical dykes and horizontal or inclined sills may only become part of the landscape once erosion removes the overlying rocks. Extrusive = lava that is in contact with the air or sea. It cools, crystallises and solidifies far quicker than magma that is still underground. The resulting igneous rocks e.g. basalt, tend to be fine grained with small crystals. **[Plate tectonic theory of crustal evolution: tectonic plates; plate movement; gravitational sliding; ridge push, slab pull; convection currents and seafloor spreading.]** Plate tectonic theory of crustal evolution: In the 1950's the worlds ocean floors were monitored and mapped from nuclear submarines. It was found that the mid ocean ridges and deep ocean trenches were seismically active. These discoveries added evidence in support to Alfred Wegner's 1912 theory of continental drift, updated in 1962 by Harry Hess. Paradigm = major theory on which lots of other theories depend on. A Paradigm shift = wrong about something big Continental drift: The continental drift hypothesis refers to the theory where at one point in time, all of the continents were joined together in one large landmass prior to splitting apart and drifting into their current positions (known as Pangea which was a super continent proposed by Wegner). He states the continents coastlines fit like a puzzle and there is geological evidence: for this such as fossil evidence and also similar fossil evidence was found in India and Antarctica. Rock formations were also found. Biological evidence: fossils of Mesosaurus were found in South America and Africa. Sea floor spreading: Hess studied the ages of rocks on the Atlantic Ocean floor. And he notices younger rocks were in the middle and the oldest were near the USA and the Caribbean. The newest rocks were still being formed in Iceland, this was compelling evidence that the Atlantic sea flood was spreading outwards from the center = Sea Floor Spreading. The rate is around 5cm a year this was confirmed by paleomagnetism. Every 400 00 years or so the Earth's magnetic field switches polarity causing the magnetic north and south poles to swap -- certain minerals known as magnetite align themselves with the Earth's magnetic field as they form. Magnetite (iron oxide) in lava erupted onto an ocean floor records the Earths magnetic orientation of that time. Sea floor spreading from mid ocean ridges is shown by mirror imaged patterns of 'switches' or reversals. Also thickness of layer of sediment deposited on ocean floor increases the further from the mid ocean ridge. Sea floor spreading and palaeomagnetic would suggest that the earth would be getting bigger were it not for the discovery of deep ocean trenches where the ocean floor was being subducted and destroyed. With all this evidence plate tectonic theory has evolved and refined and is now universally accepted. SFS evidence: is the alternating polarity of the rocks that form the oceanic crust. Iron particles in the lava erupted on the ocean floor are aligned with the earth\'s magnetic field. Ask the lava solidifies these particles provide a permanent record of the earth polarity at the time of eruption which is known as paleo magnetism. Palaeomagnetism is the record of changes in the earth's polarity and it gave rise to this idea of sea-floor spreading since this technology of seafloor mapping highlighted the earth's bathymetry and the small variations in the Earth's magnetic field which showed a striped pattern across the ocean floor. It is this symmetrical pattern of geometric reversal on either side of the mid-ocean ridge which supports this concept of sea-floor spreading. However the earth\'s polarity reverses approximately every 400,000 years and this results in a series of magnetic stripes with rocks aligned alternately towards the North and South poles. They start pattern which is mirrored exactly on either side of the Mid-Oceanic Ridge suggests the ocean crust is slowly spreading away from this boundary. Final theory of TP? = combined continental drift and sea floor spreading to propose theory of tectonic plates. Tuzo said that earth's crust, or lithosphere was divided into large, rigid pieces called plates. These plates 'float' atop an underlying rock layer called the asthenosphere. He proposed the 3 basic types of plate boundary. **[\ Tectonic plates and plate movement:]** \- The earth's surface is made up of 7 major and several minor tectonic plates. Each plate is an irregularly shaped 'raft' of lithosphere effectively floating on the asthenosphere beneath. 2 types of plat: continental over 1500 million years old, oceanic less than 200 million years old. \- Tectonic plates are large pieces of earth's crust and upper mantle and they are the sections that divide the lithosphere (the Earth\'s outer shell, including the crust and uppermost mantle). Tectonic plates are moving relative to each other and are responsible for many hazards such as volcanic activities, earthquakes and tsunamis. TP are made of oceanic crust and continental crust. \- Continental plates are permanent and makes and far beyond the margins of current landmasses. They will not sink into the asthenosphere because of their relatively low density. In contrast, denser oceanic plates are continually being formed at mid ocean ridges and destroyed in deep ocean trenches hence there relatively young age. Oceanic and continental plates move relative to each other very rates from 2 centimetres to 16 centimetres a year. \- Radioactive decay within the core of the earth generates exceptional temperatures. Hotspots around the core heat the lower mantle creating convection currents, which rise towards the surface before spreading into the aesthenosphere, then calling and sinking again. The heat from radioactive processes within the planet\'s interior causes the plates to move, sometimes toward and sometimes away from each other. \- Tectonic plates can move sideways towards each other or away from each other full stop they cannot overlap at their boundaries so must either push past each other, be pushed upwards or be forced downwards into the asanas fear and destroyed by melting. \- No gaps can occur between plates, so if they\'re moving apart, new oceanic plate must be formed. In fact because the earth is neither expanding or shrinking, and he new oceanic plate that is formed must be compensated for by the subduction destruction of an older player elsewhere. As a result zones of earthquakes, volcano and fold mountain activity are located along these great faults and it is here that most of the world\'s major landforms occur. **[Convection current:]** Convection currents, that occur within the molten rock in the mantle, act like a conveyor belt for the plates. Tectonic plates move in different directions. The direction of movement and [type of plate margin](https://www.alevelgeography.com/destructive-constructive-and-conservative-plate-margins/) is determined by which way the convection currents are flowing. The heat from the core is transferred to the mantle (aesthenosphere) via convection. Liquid rock, close to the core, is heated and rises and this magma becomes less dense as particles spread out. When it reaches the crust it is forced sideways as often it can not pass through the crust. The friction between the convection current and the crust causes the tectonic plate to move. As magma is cooler at the top as its further away from the heat source is sinks to the bottom. The liquid rock then sinks back towards the core as it cools. The process then repeats. Magma is then heated... It is said that tectonic plates are driven solely by vast, slow moving convection currents. However, convection cells are thousands of kilometres wide yet sinking to such relatively shallow depth seems implausible especially because we know of multiple convection cells beneath the Pacific plate. SO.... Convection current: earths mantle is hottest at the core so lower parts of the asthenosphere start heat up become less dense and slowly rise. As they move towards the top of the asthenosphere they cool down become more dense and slowly sink. These circular movements of semi molten rock are called convection currents. They create drag on the base of the tectonic plates causing them to move. [Possible driving mechanisms for plate tectonics:] 1\. Ocean ridge push 2\. Gravity sliding 3\. Gravitational pull [Gravitational sliding refers to when plates slide away from a spreading ocean ridge, it is a form of plate movement that is aided by the steep elevation of the ocean ridge. As fresh magma wells up at the ocean ridge at constructive boundaries to form new oceanic lithosphere, an even higher elevation is formed at the spreading ridges. Here the oceanic plate experiences a force pushing it away from the ridge known as ridge push. This new oceanic lithosphere crust slides away from the ridge and with more time and distance it starts to thicken and cool. This result in the boundary between the lithosphere and the aesthenosphere becoming deeper and as these both move away from the ridge their boundaries start to slope away from the ridge. Here gravity acts on the plates and pushes the older part of the plate to the front and this is a secondary force known as ridge push. This a force that the plates experience as they slide down the asthenosphere and under the ocean ridge. Destructive plate boundary: plate sinks into the mantle, due to negative buoyancy of the plate = slab pull. Frictional forces shallow and deep earthquakes. Now the plates experience subduction due to their weight pushing them into the mantle which is known as slap pull; the pulling force exerted on cold, dense oceanic plates plunging into the mantle.] Ridge push and GS are the same thing so...  A diagram of a volcano Description automatically generated **[Destructive, constructive and conservative plate margins. Characteristic processes: seismicity and vulcanicity. Associated landforms: young fold mountains, rift valleys, ocean ridges, deep sea trenches and island arcs, volcanoes -- identify where seismicity and vulcanicity occur e.g. volcanoes at destructive O+C so vulcanicity as well as seimmicty due to earthquakes.]** Destructive plate margins: E.g. South American plate off the coast of Chile -- oceanic and continental crust. 1. Subduction of oceanic crust beneath the continental crust. As oceanic crust is denser. 2. The exact point of collision is marked by bending of the oceanic plate to form a deep ocean trench. 3. As the two plates converge, continental land mass is uplifted, compressed and buckled and folded into chains of Fold mountains e.g. the andes -- due to excess sediment. 4. As compression continues simple folding can become asymmetrical then overfolded (making a recumbent fold). Increasing compression further would make the middle section so thin it might break nappe. 5. The oceanic crust is subducted, melted and destroyed in the asthenosphere due too high heat and pressure: zone of melting = Benioff Zone. 6. As this happens pressure builds up and volcanoes form and due too high pressure they erupt and magma explodes and erupts everywhere -- earthquakes can form here. 1. When two oceanic plates collide the heavier plate subducts underneath the lighter one and this results in formation of a deep ocean trench and melting, this results in pressure building up. 2. Here magma rises from the Benioff zone and erupts in volcanoes, the oceanic plate is broken by the volcano. 3. Lava erupts from the volcano and cools to form crescent submarine volcanoes which then can result in island arcs. 1. Continental plates are of lower density than the asthenosphere below them meaning that subduction does not occur. 2. Piles of continental crust on top of the lithosphere due to pressure between plates this results in fold mountains from powers of continental crust. The colliding plates and any sediments deposited between them simply become uplifted and buckle to form high fold mountains such as the Himalayas. There is no volcanic activity at these margins due to no subduction, but shallow focus earthquakes can be triggered. 3. Young fold mountains such as the Himalayas are continually compressing and growing higher. A diagram of continental plate with Crust in the background Description automatically generated  1. As the plates move apart due too decompression melting at a ridge e.g. Mid Atlantic Ridge the older plates are subducted by the warmer newer plates that are formed. 2. As these plates are formed new magma erupts and cools to form new land at the ridge. Less explosive underwater volcanoes formed as magma rises. 3. As the older plate is pushed away with ridge push by the newer plate gravitational sliding acts downwards onto the plate and subducts it down into the mantle and it is destroyed. 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). 4. Volcanic eruptions along the ridges can be submarine volcanoes (underwater volcanoes.) 1. These form massive rift valleys; rift valleys are formed when lithosphere stretches causing it to fracture into sets of parallel faults. 2. The land between the faults then collapses into deep, wide valleys separated by upright blocks of land known as horsts. 3. Magma erupts through the rift valley which is known as a graben this magma is slightly compressed by the horsts however magma still flows. 4. Furthermore, the rift valley may fill with water and then it will become a completely separated piece of land. Thicker continental crust falls into magma. 1. Plates move next to each other but in either different directions or at different speeds. 2. When these plates move they can create sticking with one another and this can result in increased pressure and build up which can create friction and tension resulting in earthquakes. These stresses may eventually be released suddenly as powerful shallow focus earthquakes e.g. LA in 1994. 3. Because no land is subducted or formed no landforms will be created. And there is no melting of rocks and therefore no volcanic activity or formation of new crust. Ocean ridges = longest continuous uplifted features on the surface of the planet, they are formed when plates move apart in oceanic areas. The space between the plates is filled with basaltic lava upwelling from below to form a ridge. Volcanic activity also occurs along these ridges, forming submarine volcanoes which sometimes rise above sea level. Rift valleys = such valleys form when plates move apart in continental areas. Areas of crust drop down between parallel faults to form the valley. An area between two parallel rift valleys forms an upstanding block, known as a horst. The line of the rift is thought to be an emergent plate boundary, the beginning of the formation of a new ocean as eastern Africa splits away from the remained of the continent. Deep Sea trenches = where oceanic and continental plates meet, the denser oceanic plate is forced underneath the lighter continental one. The down warping oceanic plate forms a very deep part of the ocean known as a trench. Similar process happens when two oceanic plates move towards each other. Island arcs = during subduction, descending plate encounters hotter surroundings, and this coupled with the heat generated from friction begins to melt the plate. As this material is less dense than the surrounding asthenosphere it beings to rise towards the surface as plutons of magma. Eventually these reach the surface and form complex, composite and explosive volcanoes. If the eruptions take place offshore a line of volcanic islands can form. Young fold mountains = plates forming continental crust have a much lower density than the underlying layers, so there is not much subduction when plates meet. When plates move towards each other their edges and sediment between them are forced up into fold mountains. No volcanic activity due to little subduction. Material is also forced downwards to form deep mountain roots. Sediment that have accumulated on the continental shelf, along the edge of a plate can also be uplifted as the plate edges buckle during the subduction of denser oceanic plate. A hot spot, in certain places a concentration of radioactive elements below the crust causes a hot spot to develop. From this, a plume of magma rises into the plate above. When the lava breaks through to the surface an active volcano forms above the spot. Hot spot = stationary so as the plate moves over it a volcanoe line is created The one above the hotspot is active and remained form a chain of islands with extinct volcanoes. The oldest volcanoes have pur so much pressure on the crust so subsidence has returned. volcanic activity. Hot spots   is a large plume of hot mantle material rising from deep within the Earth. Hot spots form around the core of the Earth where radioactive decay is concentrated and they generate thermal convection currents within the asthenosphere, which cause magma to rise towards the crust and then spread before cooling and sinking. This circulation of magma is the vehicle upon which the crustal plates move. Magma plume = vertical column/ upwelling of superheated rock and magma that rises up from the mantle. Volcanoes form above magma plumes. Magma plumes remain stationary overtime but the crust moves above it. Volcanic activity in the part of the crust that was above the magma plume decreases as it moves away and new volcanoes form in the part of the crust that is now above the magma plume. As the crust continues to move a chain of volcanoes are formed. The chain of volcanoes that makes up Hawaii was formed by a magma plume. This extreme heat creates magma plumes: \- These are upwellings of superheated rock that rise from deep within the Earth's mantle towards the surface \- They can break through the middle of a tectonic plate to reach the surface causing volcanic activity and earthquakes far away from plate margins \- Radioactive decay within the Earths core generates very hot temperatures, if the decay is concentrated hotspots will form around the core. These hotspots heat the lower mantle creating localised thermal currents where magma plumes rise vertically. Although usually found close to plate margins these plumes occasionally rise within the centre of plate sunburn through the lithosphere to create volcanic activity on the surface. As a hotspot remains stationary the movement of the overlying plate results in the formation of a chain of active and subsequently extinct volcanoes as the plate moves away from the hot spot. \- Tectonic plates move over the Earth\'s surface due to the process of plate tectonics. Magma plumes, on the other hand, are stationary or move very slowly. The interaction occurs when a tectonic plate passes over a hotspot. The volcanic activity associated with the hotspot leaves a record of the plate\'s movement. When a tectonic plate moves over a magma plume, it can result in the formation of various volcanic features. These may include volcanic islands, seamounts, and volcanic mountain ranges. The composition of the volcanic rocks can provide insights into the nature of the magma plume. Island Chains: \- Hot spots and magma plumes can lead to the creation of island chains such as Hawaii. \- The magma plume is stationary so when the tectonic plate moves over it, a chain of volcanoes is formed. \- The volcanoes are active when they are above the magma plume, but become extinct as the plate moves away. \- The oldest island is the one furthest away from the plume. **[Volcanic hazards:]** **[Spatial distribution of volcanoes:]** - Volcanoes are mostly found between boundary of TP, where Li causes intense heat and pressure. May form on hotspots away from plate boundaries where magma breaks through the Li. - Relationship between volcanoes and TP margins is clear. - 'Pacific ring of Fire' is a destructive boundary and shows high densities of volcanoes stretching from Aleutian Islands through Japan, Philippines and across to New Zealand -- this is an area of high volcanic and earthquake activity located in the Pacific, and the majority of large volcanoes occur within this 25,000 mile belt. - Some volcanoes occur at ocean ridges e.g. Mid Atlantic Ridge: at ocean ridges there is SFS the lava coming up from the crust is able to form volcanoes, lava has low viscosity these volcanoes have gentle slopes due to basaltic lava, these eruptions are frequent but gentle and effusive. - Some volcanoes occur at subduction zones: e.g. Ring of fire -- viscous lava which is andesitic and the eruptions are more explosive e.g. composite/ steep sided volcanoes -- oceanic continental destructive plate boundary -- these volcanoes form because visous lava forms blockages in volcanoes vents causing increased pressure and blockage is cleared by violent eruption. - Some occur at Ridge valleys: constructive margins on the continent as continental plates spread apart and rift valley forms the crust thins as it gets stretched out and magma rises through the crust e.g. Mt. Nyirigango -- great African Rift Valley. - Some volcanoes occur at Hot Spots: they are not found on plate boundaries like the one's above, hot spots create volcanoes due to radioactivity which can cause hot magma plumes e.g. in the middle of the Pacific by Hawii, hot spot heats oceanic crust and concentraction of radio active elements causes magma to break through crust and form volcanoes which are shield volcanoes -- not explosive due to runny and basaltic lava. - Although volcanic activity is common at constructive (basaltic, hot and low viscosity, frequent but not violent last for a while) and destructive (andesitic and rhyolitic lava, cooler and more viscous, erupt intermittently and are short lived) margins its absent at conservative margins and volcanoes can be located on hotspots. - Some volcanoes occur within centers of plates e.g. Hawaii hotspot, along rift valleys e.g. Great African Rift valley. - Magnitude and type of eruption vary according to location affecting type of magma e.g. basaltic lava = erupted at constructive plate boundaries, andesitic or rhyolitic lava at destructive plate boundaries. **[Magnitude:]** - Magnitude = measures amount of lava produced usually as volume or mass. - Intensity = how fast lava is produced. - Since 1982 magnitude of volcanic eruptions has been measured using logarithmic scale from 0 to 8 called VEI = combines magnitude and intensity. - 1 = gentle, 8 = mega collosal. - Hawaiian eruptions = 1. - Mount St Helens in 1980 = 4. - Super volcano e.g. Yellowstone National Park, might exceed 8. - Volcano classifications based upon violence of eruption may include a VEI rating, but are more useful is readily related to tectonics by including details of type of magma and even frequency. - VEI rating depends on: - \- amount of tephra ejected. - \- length of eruption. - \- how high tephra ejected is. - \- intense high magnitude - \- calmer, lower eruptions = effusive. **[Frequency and regularity:]** - Frequency and regularity of eruptions are rarely measurable to any degree of predictable accuracy. - Active = Active volcanoes have a recent history of eruptions; they are likely to erupt again.. Dormant = haven't erupted in a long time but are expected to erupt again in the future.. Extinct = have no potential for future eruptions Volcanoes e.g. Montserrat proved to be dormant not extinct, relying on average cycles of activity can only alert volcanologists of the necessity for heightened observation. - Mount Vesuvius carefully monitored, 70 year cycles expected -- historical records may give indications e.g. 6x 18^th^ century and 8x in 19^th^ century and 3x in 20^th^ century. Contingency plan as 3 million live within 15km of it. Current plan assumes minimum of 2 weeks warning given and foresees a week long emergency evacuation of 600 00 people from red zone -- greatest risk from pyroclastic flows or nee ardente. **[Frequency:]** - Frequency of eruptions varies per volcano and largely depends on the location of volcanoes. - Volcanoes are classed: active, dormant or extinct. - Volcanic eruptions are frequent as estimated that 50-60 erupt each month. - Usually a higher frequency eruption means eruptions are effusive whereas low frequency means they are explosive. - Frequency is influenced by: magma viscosity, gas content and the type of volcano. **[Regularity:]** - Volcanic eruptions are regular in that the eruptions on each type of boundary are similar (e.g. eruptions on destructive boundaries will regularly be explosive). - Sometimes eruptions may be irregular and not fit patterns. - Some small volcanoes only erupt once in their lives, while other volcanoes erupt multiple times. Kilaeua volcano in Hawaii, which has been erupting continuously since 1983, is the world\'s most active volcano. While some volcanoes erupt at regular intervals, there are always exceptions to the rule. **[Predicting volcanic eruptions:]** - Volcanic eruptions tend to follow weeks of seismic activity and other warning signs: e.g. rising magma which can be detected by heat sensors and satellites, ground deformation as rising magma causes bulges, increased emissions of sulphur dioxide and other gases, increased seismic activity cause by magma movement detected by seismometers. - As long as active and dormant volcanoes are monitored using equipment e.g. seismometers and seismographs, warnings of imminent eruptions can be issued to governments and civil authorities. Prediction is generally very successful and can be aided by evidence from previous eruptions e.g. lahar and pyroclastic deposits following river valleys. - Part of continency planning, hazard maps can be produced to identify those areas most at risk, which are therefore prioritize for evacuation to safe zones. - Regularity of eruptions can help estimate when eruptions will take place (i.e. every 10 years). Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption. What is being monitored? What does it indicate? ------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Seismic activity measured using seismometers and recorded using seismographs. Micro quakes indicate rising magma fracturing and cracking the overlying rocks. Ground deformation is measured using tiltometers and laser -- based electronic distance measurement. Bulging of the ground is caused by rising magma. Both slop angles and increasing distance between set points can be measured very accurately. Upward movement of iron -- rich magma is measured using magnetometers. Changing magnetism within the volcano is a common geophysical indication of rising magma. Rising ground water temperature and/ or gas content is measured using hydrological instrumentation. Rising magma will heat ground water and corrupt it with gases e.g. sulphur increasing acidity. Warning signs: small eruptions, emissions of gases, landslides and rockfalls can be recorded in real time using remote sensing equipment. Remote solar -- powered digital camera surveillance is a powerful and safe tool to record physical changes in and around the main crater. Thermal imaging and gas sampling of emissions e.g. chlorine can also be included in remote sensing. **[The nature of vulcanicity and its relation to plate tectonics -- spoken about above e..g destructive nature of volcanicty is low viscosity and very powerful:]** Volcanicity refers to the processes and phenomena associated with volcanic activity, including the eruption of magma, gases, and ash onto the Earth\'s surface or into the atmosphere. The relationship between volcanicity and plate tectonics is profound and can be understood through the movement and interactions of Earth\'s tectonic plates. (also spoke about above in spatial distribution). 1\. Subduction Zones and Volcanic Arcs: At convergent plate boundaries where one tectonic plate is forced beneath another (subduction), magma is generated as the subducted plate heats up and releases volatiles (water, carbon dioxide). This magma, being less dense than the surrounding rock, rises through the overlying plate, leading to the formation of volcanic arcs. The Andes in South America and the Cascade Range in the Pacific Northwest of the United States are examples of volcanic arcs formed due to subduction. most powerful and destructive potential is high due to andesitic lava. 2\. Mid-Ocean Ridges and Divergent Boundaries: Along mid-ocean ridges, which are divergent boundaries where tectonic plates move away from each other, magma from the mantle rises to fill the gap created by the separating plates. This process results in the creation of new crust and the formation of underwater volcanic features like seamounts and shield volcanoes. The Mid-Atlantic Ridge and the East Pacific Rise are examples of such volcanic activity. 3\. Hotspots: Hotspots are areas where magma rises from deep within the mantle to the Earth\'s surface, creating volcanoes. These hotspots are believed to be relatively stationary compared to tectonic plate movement. Over time, as the tectonic plate moves over the hotspot, it creates a chain of volcanoes. The Hawaiian Islands, formed by the movement of the Pacific Plate over the Hawaii hotspot, are a classic example. Volcanicity is intricately linked to the movement and interactions of tectonic plates. It\'s the result of the Earth\'s internal heat, which drives the circulation of mantle material, causing magma generation and subsequent volcanic eruptions. The various types of volcanoes and volcanic activity observed worldwide are directly related to the specific plate tectonic settings in which they occur. **[Forms of volcanic hazard: nuées ardentes, lava flows, mudflows, pyroclastic and ash fallout, gases/acid rain, tephra:]** Primary effects are brought about by the material ejected from the volcano = tephra, pyroclastic flows, lava flows, volcanic gases. Secondary effects = lahars, flooding, volcanic landslides, tsunamis, acid rain, climatic change. **[Nuées ardentes/ pyroclastic flows:]** - Both terms are used to describe the extremely dangerous and fast-moving mixtures of hot gases, ash, volcanic rocks, and other volcanic particles that can flow down the slopes of a volcano during an eruption. - A pyroclastic flow is a dense, fast-moving flow of solidified lava pieces, volcanic ash, and hot gases. It occurs as part of certain volcanic eruptions. A pyroclastic flow is extremely hot, burning anything in its path. It may move at speeds as high as 200 m/s. Pyroclastic flows form in various ways = a super-heated mixture of gas and tephra. 800 degrees, high velocity. 700km/hour -- Pompeii was destroyed by these - A nuée ardente (burning clouds) is a turbulent, fast moving cloud of hot gas and ash erupted from a volcano. - Associated with explosive volcanic eruptions, occur when pressure within crater high violent eruption of gases, ash and volcanic rocks atmosphere they collapse under their own weight dense fast-moving cloud down volcano slope. - This is one of the deadliest volcanic hazards as they can travel long distances and destroy everything in their path. - E.g. when Fuego volcano erupted in Guatemala in 2018, pyroclastic flows destroyed several nearby towns. - Accumulation of ash at crater -- collapses and flows downhill. **[Lava flows:]** - Lava flows refer to the movement of molten rock, called lava, that emerges from a volcanic vent or fissure onto the Earth\'s surface during an eruption, runs down surface of volcano. - Lava flows travel at different speeds depending on slope, temperature and viscosity. - Most move slowly enough that they are not a risk to human life but can cause significant damage to property and infrastructure e.g. burying buildings roads and land. - The fastest flows can reach speeds of up to 60 mph. - In the 2021 eruption of Mount Nyiragongo in the Democratic Republic of Congo, lava flows travelled almost 10km destroying properties and killing over 30 people. - Composition and type: - Lava flows can have different compositions, primarily classified as basaltic, andesitic, or rhyolitic based on their silica content. - \- Basic lava = fast moving, hot and fluid, can create wildfires -- rich in iron and magnesium. - Basaltic lava, being less viscous, tends to flow more fluidly and can cover large areas, creating broad, low-profile shield volcanoes. It is also very hot at around 1200 degrees. Has a low silica content around 45 -- 55%, eruptions are effusive and regular -- lava can flow over large distances. - \- Andesitic = intermediate viscosity with intermediate silica content -- 55%- 65%, lava temperature between 800 -- 1000 Celsius, eruptions can be very destructive specially when volcano has been formant and hasn't erupted recently. - Rhyolitic lava = are more viscous and tend to form steeper-sided stratovolcanoes due to their ability to pile up around the vent, it's magma is more viscous/thick and high viscosity is related to high silica content 65 -- 75%. Silica originates from the destruction and melting of plates. Rhyolitic magma traps gas and coagulates up in the vent of the volcano. Pressure builds up over time until it is suddenly released in a catastrophic eruption. Lavas have relatively low temperatures of between 650 and 900°C, flow slowly and can damage property. Large explosive eruptions can be highly dangerous. **[Mudflows/lahars:]** - Mudflows possess great destruction power = fast moving mixtures of water, rock debris and mud. - Mudflows typically occur on volcanic slopes or in areas with loose, unconsolidated materials, especially after heavy rainfall or during volcanic eruptions. They can form when water saturates loose materials, causing them to become extremely fluid and flow rapidly downslope. - Mudflows consist of a mix of water, mud, rock fragments, and other debris. They can move at high velocities, sometimes reaching speeds of tens to hundreds of kilometers per hour. Their high velocity and fluidity make them extremely destructive as they can carry large boulders, trees, and debris, causing extensive damage to structures and infrastructure in their path. - Indonesia called lahars, lahars = more specifically to flows of ash, cinder, soil and rock that have been changed to clay by acids in volcanic gases and hot spring waters. - Lahrs have destroyed more property than any other colonic action and killed thousands. - mudflows that occur when tephra mixes with water, either from rainfall, or from melted snow and ice - They are fast flowing and destroy everything in their path - E.g. the lahars that occurred when Mount Pinatubo erupted in the Philippines in 1991 caused extensive damage and disruption - Common causes: eruptions ejecting directly from crater lake, or through the broken crater walls, rapid melting of ice or snow on the volcanoes slopes, eruption -- induced heavy rainfall mixing with loose material on volcanoes slopes, pyroclastic flows (nuees ardentes) entering streams. - Colombian Armero tragedy of 1985: illustrated destructiveness of lahars. Rising magma and gas and steam emissions started melting summit glacier of Nevado del Ruiz which hadn't erupting since 1595. Melting continued until the full eruption of the 13^th^ of November that melted remaining snow and ice. Resulting meltwater + torrential rain + flood water from river mixed with ash from previous eruptions 30m high lahar at 80km per house Armero -- at night. 21 000 perished. **[Ash fallout:]** - Large quantities of ash carried by the wind and deposited on the ground -- happens immediately after eruption and is controlled by particle density. - It can travel many km, causing respiratory problems, injuries, damage, deaths and disruption to transport also due to the large weight of ash this can collapse buildings. - Ash = microscopic shards of glass, spread around large areas of the atmosphere by wind currents, can envelope the entire planet - E.g. the 2010 Eyjafjallajökull eruption in Iceland produced an ash cloud that disrupted air travel in Europe for several weeks. - Aviation = clogs jet engines. - E.g. Mount St Helens. - Climate change = 1991 Mt. Pinatubo 0.5 degrees fall in average global temperature for 3-4 years. - This can also refer to volcanic ash ejected from the volcano can rise up and form an eruption column up to 45km into the atmosphere. **[Pyroclastic fallout (same/ similar to ash fallout):]** - Particles that have been ejected from volcanic vents and have traveled through the atmosphere before falling to earth or into water. **[Gases/ acid rain:]** - Acid rain forms when sulphur dioxide emitted during the eruption reacts with water vapor in the atmosphere to form sulphuric acid. - It can damage crops, forests and aquatic ecosystems. - Volcanoes co2 = carbonic acid, NOx = nitric acid, SO2 = sulphuric acid, H2O = water acid rain - Volcanic Gases: Volcanic eruptions release a variety of gases into the atmosphere, including water vapor, carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen sulfide (H2S), and others. These gases can have immediate and long-term effects on the environment and climate. Sulfur dioxide, in particular, can contribute to the formation of sulfuric acid aerosols, affecting air quality and potentially leading to the formation of acid rain. - Industrial and Human-Generated Gases: Human activities, such as burning fossil fuels, industrial processes, and transportation, release gases like sulfur dioxide, nitrogen oxides (NOx), and carbon monoxide (CO) into the atmosphere. When these gases react with water vapor and other atmospheric components, they can form acid rain. - Acid Rain Formation: Acid rain is a result of pollutants, especially sulfur dioxide and nitrogen oxides, mixing with water vapor and other atmospheric components. These pollutants undergo chemical reactions in the atmosphere, forming sulfuric acid and nitric acid, which then fall to the Earth\'s surface as acid rain. **[Tephra:]** - Tephra refers to fragmented material ejected during a volcanic eruption, encompassing a range of particle sizes and compositions. - Tephra is any material ejected by a volcano into the air. This can be anything from fine ash to large volcanic bombs. Tephra is hazardous as it can cover agricultural land, destroying crops. It can also cause airspace to be closed. - The composition of tephra can vary depending on the type of eruption, the magma\'s composition, and the eruptive style. - Tephra poses various hazards to both local and distant areas. Ashfall can disrupt air travel by damaging aircraft engines and reducing visibility. Accumulation of ash on roofs can lead to structural damage due to its weight. Additionally, respiratory problems can arise from inhaling fine ash particles. Larger tephra particles, such as volcanic bombs, can cause damage to infrastructure and pose risks to human safety. - Tephra fallout affects ecosystems by smothering vegetation, altering soil properties, and disrupting natural processes. However, over time, volcanic ash can also provide nutrients to the soil, aiding in long-term fertility. Different types of volcanoes: \- Fissure eruptions of basic lava can create extensive lava plateaus. Hollows in the existing landscape are filled to create flat, featureless basalt plains e.g. Deccan Traps in Central India -- here there are multiple layers of basalt. The impact of fissure eruptions cannot be underestimated. They represent the largest contributors to global climate change and large-scale landscaping. Shield volcano: - They are low and the largest, broad and gentle slopes , usually located on constructive plate margins or hotspots, tend to erupt frequently due to fluid nature of basaltic magma. - Form when you have liquid lava which travels far and solidifies. - Lava flows spread out over wide areas broad, dome shaped volcano, formed through accumulation of low viscosity lava (basaltic). - They produce fast flowing basaltic lava low in silica is fluid and flows easily -- lava travels long distance before cooling. - Usually found at divergent plate boundaries, and sometimes at volcanic hotspots: Hawaiian Islands. - Basic shield volcanoes = formed by relatively pure basalt that cools as it runs down summit crater. Typical at constructive PM, rift valley and hot spot, impact is more obvious by vast scale of resulting volcanic cones. Can become tourist attractions. - Most are effusive.  Diagram of a magma chamber Description automatically generated Caldera: - This is a volcanic crater. - Violent eruptions blow off volcanoes summit emptying magma chamber around the side of volcano collapse inwards pit crater that can be many km in diameter and is left to be flooded by sea or fill as a lake e.g. Santorini. - Large and round, has a collapsed magma chamber on the top, form when large amounts of magma erupt over a short period of time, removing structural support of the rock above collapse. - Circular depression forms when a volcano erupts explosively cast magma from beneath surface is release. During eruption empties magma chamber which cant support weight of overlying volcanic structure bowl shaped depression.  A diagram of a volcano Description automatically generated Stratovolcano (composite): - Known as composite volcanoes, large and steeper slopes as a result of repeated eruption of ash, tephra and lava which builds up the volcano in layers and solidification of lava overtime, tend to have the most explosive eruptions. They are located on destructive plate margins and tend to erupt infrequently due to viscous: rhyolitic or andesitic magma. - The eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow. - Plates descend deep into the mantle and melt due to the surrounding heat and friction from the subduction process. The less dense magma, rich in silica formed here, rises to the surface to create composite volcanoes with a gaseous, explosive nature. The accumulating layers of lava -- ash -- lava -- ash... gives these volcanoes their name ('composed' of many layers).Layering weaknesses that can be exploited by magma conical shapes are rare. - Tall and conical, steep slows and symmetrical shape. - Formed by alternating layers of lavas flows, ash and other materials. - Thicker lava e.g. andesitic and rhyolitic, doesn't flow as far. - E.g. mount Etna.  A diagram of a volcano Description automatically generated Cinder cone: - Simplest type of volcano, built from blobs of cooled lava ejected from a single vent. - Relatively small and steep sided, conical shape, composed of loose fragments of volcanic material e.g. cinders and ash. - Smaller than strato and shield. - As the lava is launched violently into air it breaks into small fragments that solidify and fall as cinders around the vent circular/ oval cone. Acid dome volcanoes: - Are steep sided convex associated with thick/ viscous, silica rich gaseous lava that solidifies before running too far down the slope. Associated with destructive plate margins they have explosive eruptions of pyroclastic flows which have deadly impacts. E.g. Mount Pelée in Martinique pyroclastic flows killed 30 000 people. Glacial floods: - Glacial floods occur when temperature rises due to the magma heating it and ice sheets or glaciers quickly melt this results in lots of water being discharged. A table with a chart of lava Description automatically generated with medium confidence Eyjafjallajökull, Iceland, April 2010: Eyjafjallajökull is one of a number of volcanoes in Iceland covered by great thickness of ice. Subglacial eruptions cause the ice to melt, this can lead to considerable flooding. Following preliminary seismic activity and small fissure eruptions in March 2010, Eyjafjallajökull eruptions caused torrents of meltwater to wash away part of Iceland's main perimeter road. No deaths/ injuries reported but 800 people were evacuated. Thick deposits of ash farming being impossible and contaminated water sources with fluoride. Winds carried the ash cloud south and east towards Europe, causing the progressive closure of airspace over the space of a week. A total of 100 000 flights were cancelled and over 10M people left stranded and airlines lost US\$1.7B in revenue. Cargo and freight traffic were also disrupted, affecting movement of fresh produce e.g. Kenyan farmers were laid off as the fresh vegetables and flowers they produced for European markets couldn't be transported. Travel and tourism industry faced massive payouts in compensation and even schools faced disruption as pupils and teachers were stranded abroad following Easter holidays. Mount Merapi, Java, October 2010: Mount Merapi, on the island of Java is the most active volcano in Indonesia. It erupts frequently and violently and represents a constant threat to the tens of thousands of people who live and farm here due to its fertile soils. In October 2010 after more than 500 earthquakes were registered beneath the volcano, the evacuation of 20 000 villagers living within a 20km radius was advised. Within days a series of powerful eruptions began, which over subsequent weeks blasted pyroclastic flows down the strato -- volcano's flanks. Fires, burns, respirator failure and blast injuries 350 fatalities, most commonly to those who had refused to evacuate or had returned to their homes between eruptions. In total around 350 000 people were displaced as their homes were destroyed and farmland was smothered in thick deposits of ash and lava bombs. **[Impacts: primary/secondary, environmental, social, economic, political.]** +-------------+-------------+-------------+-------------+-------------+ | Effect: | Environment | Economic: | Social: | Political: | | | al: | | | | +=============+=============+=============+=============+=============+ | Primary: | \- Damaged | \- | \- People | \- | | | ecosystems | Businesses | killed -- | Government | | (immediate) | through | and | this can | buildings | | | various | industries | happen by | and other | | | volcanic | are | tephra, | important | | | hazards. | destroyed | lava flows, | areas | | | | or | pyroclastic | destroyed | | | \- Wildlife | disrupted. | flows or | or | | | killed. | | increased | disrupted. | | | | \- | CO2 levels | | | | \- Crops | Destruction | which can | \- Disaster | | | can also be | of | cause | plans | | | damaged and | livestock | suffocation | coordinated | | | water | and |. | by the | | | supplies | livelihoods | | government. | | | contaminate |. | \- Homes | | | | d | | destroyed | | | | by ash | | from lava/ | | | | fall. | | pyroclastic | | | | | | flows which | | | | \- Ash fall | | results in | | | | can | | evacuation. | | | | contaminate | | | | | | air, water | | \- Lava and | | | | and soil. | | pyroclastic | | | | | | flows can | | | | \- | | destroy | | | | Pyroclastic | | roads and | | | | flows can | | cause | | | | result in | | buildings | | | | severe | | to | | | | destruction | | collapse. | | | | of eco | | | | | | systems and | | | | | | burial of | | | | | | landscapes. | | | | +-------------+-------------+-------------+-------------+-------------+ | Secondary: | \- Water | \- Jobs | \- Fires | \- | | | acidified | lost. | can start | Conflicts | | (days -- | by acid | | which put | concerning | | weeks after | rain as | \- Profit | lives at | government | | eruption) | well as | from | risk. | response, | | | soil. | tourism | | food | | | | industry. | \- | shortages, | | | \- Volcanic | | Disruption | insurance | | | gases | \- Costs of | of | etc. | | | contribute | reconstruct | essential | | | | to | ion. | services. | \- | | | greenhouse | | | Government | | | effect. | \- Economic | \- May | must deal | | | | strain on | result in | with this | | | \- Also | local and | health | well and | | | fires caused | regional | issues e.g. | there may | | | by lava | food | waterborne | be unrest | | | flows and | production. | diseases. | due to | | | pyroclastic | | | dissatisfac | | | flows, which | \- | \- Mudflows | tion | | | can then | Unemploymen | or floods. | with | | | spread out | t | | disaster | | | of control, | increases | \- Trauma. | response. | | | and acid | and can | | | | | rain as a | lead to | \- | \- Seeking | | | result of | income | Homelessnes | aid and | | | SO2 being | inequality. | s. | cooperation | | | released | | | from other | | | into the | | \- Lahars | countries, | | | atmosphere. | | often occur | diplomatic | | | | | when | challenges. | | | \- Lava | | volcanic | | | | flows and | | material | | | | ash fall | | mixes with | | | | can affect | | water from | | | | soil | | rainfall or | | | | fertility. | | snowmelt. | | | | | | These | | | | \- | | fast-fl | | | | Respiratory | | owing | | | | issues and | | rivers of | | | | disruption | | mud can | | | | of eco | | kill and | | | | systems | | injure | | | | from | | people. | | | | ashfall. | | | | | | | | \- They can | | | | \- Flooding | | cause | | | | from | | further | | | | glacial | | destruction | | | | regions. | | to roads | | | | | | and | | | | | | buildings, | | | | | | making it | | | | | | difficult | | | | | | for | | | | | | emergency | | | | | | services to | | | | | | reach | | | | | | people in | | | | | | need, and | | | | | | lead to | | | | | | businesses | | | | | | being | | | | | | destroyed, | | | | | | causing | | | | | | high levels | | | | | | of | | | | | | unemploymen | | | | | | t. | | | | | | | | | | | | \- People | | | | | | can | | | | | | experience | | | | | | psychologic | | | | | | al | | | | | | problems if | | | | | | they lose | | | | | | their homes | | | | | | or lose | | | | | | relatives | | | | | | and friends | | | | | | in the | | | | | | eruption, | | | | | | and there | | | | | | may be a | | | | | | shortage of | | | | | | food, | | | | | | particularl | | | | | | y | | | | | | if the area | | | | | | is | | | | | | dependent | | | | | | upon | | | | | | agriculture | | | | | |. | | | | | | | | | | | | \- May | | | | | | result in | | | | | | conflict | | | | | | between | | | | | | locals and | | | | | | increased | | | | | | crime | | | | | | rates. | | +-------------+-------------+-------------+-------------+-------------+ **[Short and long-term responses: risk management designed to reduce the impacts of the hazard through preparedness, mitigation, prevention, and adaptation.]** Short-term responses mainly involve evacuation, search and rescue and providing aid to those affected. Long-term responses go on for months and years after a disaster. It involves constructing destroyed houses, schools, hospitals, etc. Short term responses: evacuating people following a warning, although this is mainly limited to volcanic eruptions as earthquakes occur without warning. They also include the search and rescue effort, trying to rescue people trapped under rubble for example, as well as using social media to aid search and rescue operations. In addition, they include medical care for the sick and injured, this might by in the form of checking people for broken bones, administering pain killers or antibiotics, or performing emergency surgery. Furthermore, they also include providing temporary shelter for those who have lost their homes, usually in the form of large community buildings. Finally providing food and clean bottled water is an important part of the immediate response effort as food and water supplies are often destroyed in a hazard event. The main aim of immediate responses are to minimize the loss of life. Usually in low income countries the victims are dependent on support from high income countries, so emergency aid may take a few days to come through, which is one of the reasons the death toll in LIC events tends to be higher. Long term responses: Long-term responses are those that take place in the weeks and months after a hazard event, and focus on the re-building and reconstruction of areas that have suffered extensive damage. The aim is to help people return to their normal lives as quickly as possible, and to also reduce the risk of damage from natural hazards in the future. Long-term responses include restoring essential utilities that have been affected by the tectonic hazard event, for example repairing gas mains and electricity cables, to ensure that energy sources are restored, as well as repairing water pipes to make sure that people are not without a supply of drinking water for too long. Buildings have to be repaired or rebuilt -- both domestic and commercial properties, but also there is the repair of transport infrastructure too, including roads and railways -- this is extremely important as damaged infrastructure makes it very difficult to bring in emergency supplies. This process is very costly so can take years to happen in LICs. Another response is working to rehome people who are living in temporary accommodation. In 2021 Haiti was hit by a large earthquake -- many of the people affected were still living in temporary accommodation following the devastating earthquake of 2010. Finally, long-term responses also include putting measures in place to minimize future risk of damage or loss of life, through monitoring, prediction, protection and planning. **[Types of risk management designed to reduce the impacts of the hazard:]** **[Preparedness:]** \- Monitoring increases in the notice of volcanic eruptions meaning warnings can be given out. \- Education on volcanoes in areas of risk so people are aware and know how to react. \- Evacuation procedures planned. \- Training response teams. \- In the short term: make sure people are prepared and can keep track of volcano, follow advice from authorities. \- Emergency plans for local communities/ household. \- Homes can be secured to reduce the impact e.g. build with solid material. **[Mitigation:]** \- Invention to the volcano for example concrete blocks to stay lover away from areas at risk. \- Strengthening buildings about are at risk of mud flows or ash pile up. \- Evacuation and exclusion zones. \- Mitigating effects on health by having emergency aid and rescue. \- Implementing sophisticated monitoring systems that can detect volcanic activity to provide crucial time for evacuation. \- Hazard zoning to restrict development on high risk areas. \- Designing infrastructure to be as least vulnerable as possible. **[Prevention:]** \- Volcanic eruptions cannot be prevented. \- Only the risk to people can be prevented by not allowing people near volcanic hazards e.g. preventing building around volcanoes. **[Adaptation:]** \- Move away from area at risk. \- Capitalize on opportunities e.g. encourage tourism. \- Change profession so it is less likely to be affected by volcanic hazards. \- Have an emergency plan, make sure possessions are in the bank. \- Construct resilient buildings and diversify crops and use agricultural adaptation. \- Awareness and education. \- Tourism management e.g. guided tours to volcanoes. **[Protection:]** \- Protection usually means preparing for the event, through monitoring and risk assessments as well as alert levels in order to warn the public of the threat. [Iceland: Living with Volcanoes] Landscapes due to volcanic activity: - Iceland is at a divergent margin and located on top of a Hotspot Volcanoes Why live near volcanoes: - Flat and fertile land allows growth of rape seed used for biodiesel and oil for cooking -- land is part of a glacial plate, underneath crops is land rich in ash and minerals. - Gives more than it takes: hot water for house (heated by geothermal energy) volcanic activity heats bed rock any water permeating into it steam, water from glacier, electricity andS shelter from winds and good views. - Energy prices 1/3 of the UK. - Lots of tourism provides employment. - Many different types of volcanoes and makeup and location affects eruption which affects amount of ash, lava, and floodwater it produces. - Lava pushed out of fissure: lava fountains erupt for many weeks and can become tourist attractions lava is basaltic, high temperature, low silica so isn't very explosive. - Heimaey: volcano erupted underneath ice: fissure ripped the island of Heimaey open fountain of lava engulfed 100 houses and lots of wildlife, 5400 population 1800 and reshapes land. Glacial outburst flood in volcanic context maximum output in 10 minutes to an hour, water destroys land, houses. Rising magma cools by water it fragments particles of ash which cloaked many infrastructures and can damage engines. - Huge amounts of ice were melted causing floods to rush down nearby rivers 1000 people were evacuated - As the eruption continued, large quantities of ash poured from the volcano into high levels of the atmosphere, once picked up by the jet stream this ash cloud was blown towards Europe, cost of airlines was around £130M per day - Risk was very low as few people lived in this part of the island, real threat was ash clouds meaning people who live far away were still at risk especially because travel and transport were reduced due to engines being clogged. - Using monitoring advanced warning. - Practice evacuations shelters. - Well trained teams and good quality equipment and regular team meetings. - GPS monitoring station detects changes in heigh to land and combined with other data effective. - Better ash modelling and latest radars are 3d showing location and height of ash particles reduced size of locations that need to be avoided reducing impacts on air travel more precise and minimise disruptions. - Building levees and removing materials from flood routes channels meltwater more efficiently and to control flooding make rivers deeper and narrower. - Cool lava with water to cool it create dam and saves infrastructure. - Ash (minerals in ash) fertile soil increasing plant growth -- increasing crop yield due to ash fertilizer. - Increased tourists due to increased publication can buy ash -- visitor centres. - Diversification = multiple sources of income. - Data centre: low cost electricity for many companies save 82% of electricity -- geothermal energy = reliable and green. - Rural de population due to seasonal tourism. **[Impacts (primary/secondary: social, economic, environmental, political) and human r