Natural Hazards

• What is a natural hazard A natural hazard is a natural event such as an earthquake, volcanic eruption, tropical storm or flood that has the potential to cause death and damage.
• How can natural hazards be classified · Tectonic hazards · Atmospheric hazards · Geomorphological hazards · Biological hazards
• Give 4 reasons why the incidence of natural hazards is increasing. ⁃ Global warming ⁃ Deforestation ⁃ Urbanisation Population increase
• What factors affect hazard risk? An increase in the number of people vulnerable to the natural hazard (e.g. population growth & increased population density close to hazard-prone areas) An increase in the frequency and magnitude of the natural hazard A decrease in the number of people capable of coping with the natural hazard
• What is the structure of the Earth? ⁃ Inner core ⁃ Outer core ⁃ Mantle ⁃ Crust
• What are the characteristics of the inner core? Solid mass of iron and nickel. Hottest part of the Earth. Temperatures up to 5,550°C.
• What are the characteristics of the outer core? Layer surrounding the inner core. Liquid layer of icon and nickel.
• What are the characteristics of the mantle? Thickest section of the Earth. Approximately 2900km.Made up of semi-molten rock called magma.
• What are the two types of crust called? Oceanic and Continental
• Continental vs Oceanic Continental - Less dense than oceanic crust - Thicker than oceanic crust - Lighter than oceanic crust - Forms the Earth’s continents - Older than oceanic crust
• Types of plate margins Constructive Desctructive Conservative
• Give two possible reasons why plates move Convection currents & Slab pull (+ ridge push).
• What is ridge push Ridge push – magma rises as the plates move apart. The magma cools to form new plate material. As it cools It become denser and slides down away from the ridge. This causes other plates to move away from each other
• What is Slab pull The denser plate sinks back in to the mantle under the influence of gravity. It pulls the rest of the plate along behind it.
• Where in the world are the majority of the Earth’s volcanoes and earthquakes found? The majority of the Earth’s volcanoes and earthquakes occur around the Pacific Ring of Fire.
• Describe the global distribution of volcanoes and earthquakes Earthquakes are found along all types of plate margins. Volcanoes however, only occur at constructive and destructive plate margins. Volcanoes are also found away from plate margins at volcanic hot spots such as Hawaii in the Pacific Ocean.
• Describe the physical processes that happen at constructive plate margin. magma rises between two tectonic plates.The plates move away from each other due to ridge push and slab pull.The magma cools to form new plate.On land, rift valleys form such as the East African rift valley. Where two oceanic plates move apart new islands can be formed e.g. Iceland
• Give an example of two tectonic plates that form a constructive plate margin North American and Eurasian Plate South American plate and African Plate Pacific plate and Nazca plate Cocos plate and Pacific plate.
• Identify the type of volcano that forms on constructive plate margins Shield volcanoes
• Plate tectonics theory? Older denser tectonics plates sink into the mantle at subduction zones causing newer less dense sections to be pulled along.
• Describe the physical processes that happen at a destructive plate margin. When oceanic and continental plates collide the denser oceanic plate subducts the continental plate and enters the mantle where it melts.Magma can rise through the lithosphere and erupt as lava through volcanoes.As the oceanic plate subducts, it gets stuck due to friction. Pressure builds up until it is released as an earthquake.
• Give an example of two tectonic plates that form a destructive plate margin Pacific and Eurasian plate Nazca and South American plate Philippines and Eurasian plate Indo-Australian and Pacific plate.
• Identify the type of volcano that form on destructive plate margins Composite volcano
• Describe the physical processes that happen at a conservative plate margin. At a conservative margin two plates move parallel to each other.They can be moving in the same or opposite directions. Pressure builds along the margin of tectonic plates.As friction is overcome the rock fractures releasing energy as an earthquake
• Give an example of two tectonic plates that form a conservative plate margin. North American and Pacific plates Cocos and Nazca plates Arabian and Indo-Australian plates African and Eurasian plates
• Why are volcanoes not found along conservative plate margins? The main reason for this is that no volcanic activity occurs at the margin, only earthquakes. This is because a conservative plate margin, sometimes known as a transform fault, is where two plates shear past each other without direct collision.
• What is the difference between a primary and secondary effect of natural hazard? primary effects - things that happen immediately as a result of an earthquake secondary effects - things that happen in the hours, days and weeks after the initial earthquake
• Give three examples of primary effects of earthquakes - Property, buildings and homes destroyed - People injured and killed - Ports, bridges, roads and railways damaged - Pipes (water & gas) and electric cables broken
• Give three examples of secondary effects of earthquakes - Business reduced, and money spent repairing damage, so the economy slows - Emergency services are hindered by blocked transport infrastructure leading to more casualties - Broken gas pipes and fallen electricity cables cause fires leading to further injuries, death and damage - Disease spreads due to the lack of clean water as water pipes are damaged and poor sanitation
• Give three examples of primary effects of volcanic eruptions. - People and livestock injured and killed. Property and farmland destroyed. This is due to lava and pyroclastic flows and ash causing buildings to collapse - Contaminated water supplies from ash fall and the release of gases such as Sulphur dioxide - Airspace closed due to the risk of volcanic ash in the atmosphere affecting engines
• Give three examples of secondary effects of volcanic eruptions. - Economy slows due to the impact of the volcanic eruption on infrastructure - Snow and ice caused to melt causing widespread flooding. Ash mixes with flood water causing lahars (mudflows) destroying property and killing people - Tourism increases as people want to visit places affected by volcanic eruptions - Soil becomes more fertile as volcanic ash provides
• Give three immediate responses to tectonic hazards. - Issue warnings to those at risk - Rescue teams search for survivors - Injured receive treatment - Shelter, food and drink provided - Recover bodies - Fight fires
• Give three long term effects of a tectonic hazard. - Buildings and transport infrastructure repaired and rebuilt - Regulations and building codes improved - Utilities such as gas, electricity and water restored - Resettle local people affected by the tectonic hazard - Develop strategies to recover the economy - Install and/or upgrade monitoring technology
• Give 3 reasons tectonic hazards tend to have a greater impact in LICs than HICs - Poor construction standards - Corruption, particularly in planning and construction - Monitoring and prediction systems are less developed - Medical facilities cannot cope with the influx of injured people - There is a lack of resources / finances to effectively respond following a natural disaster Poor transport infrastructure
• Give 3 economic reasons why people live in areas at risk of tectonic hazards - Geothermal energy provides employment opportunities and energy for the area - Nutrient rich soil provide ideal conditions for agriculture - Mining provides income and energy - Jobs are created in tourism which provides income for locals - Moving may be expensive
• Give one social reason why people live in areas at risk of tectonic hazards - People want to be close to friends and family - Local people may not understand the risk, or the threat may not be great enough - People may feel confident that their properties will keep them safe
• Identify the 3 categories used to reduce the risks associated with tectonic hazards - Monitoring and prediction - Protection - Planning
• What is monitoring and prediction Monitoring and prediction = Monitoring involves using technology to observe earth tremors. Prediction involves experts using this data to calculate where earthquakes are likely to happen, however it's very difficult to predict when they will happen.
• What is protection Protection = Many areas prone to earthquake hazards now use building codes. Any new building or adjustment to existing buildings must be built to strict guidelines that would protect people from future earthquake hazards. Protection involves constructing buildings so that they are safe to live in and will not collapse.
• What is planning/preparation Planning/preparation = Hospitals, emergency services and residents practise for an earthquake in earthquake-prone countries. They have drills in all public buildings so that people know what to do in the event of an earthquake. This helps to reduce the impact and increases people's chance of survival.