Hazards: EGC All Quizlet Flashcards
Natural hazard
An event caused by natural processes that is a threat to people and property.
Natural disaster
A natural hazard becomes a disaster if there is a significant impact on people and property. According to the UN, this is when 10 or more people are affected, 100 or more people are affected, or the government declares a state of emergency.
Primary impacts
Have an immediate effect on the affected area and are a direct result of the event.
Secondary Impacts
Happen after the disaster has occurred or are a knock-on effect of the disaster.
Geophysical hazards
Driven by the earth’s own internal energy sources e.g., plate tectonics, volcanoes, seismic activity (earthquakes).
Atmospheric hazards
Driven by processes at work in the atmosphere e.g., tropical storms, droughts
Hydrological hazards
Driven by water bodies, mainly oceans, e.g., floods, storm surges, tsunamis.
Hazard perception
The way in which people receive and process information about a potential hazard and make sense of it. How people respond to a hazard links to their perception of the risk. Perception is influenced by a range of factors including socio-economic status, education, religion and cultural background.
Hazard risk
The probability/chances of a hazard event occurring and creating loss of lives and livelihoods.
Hazard vulnerability
The ability/inability to resist a hazard and respond when a disaster has occurred. Can be described as insecurity.
Economic determinism
The view that the wealth of an individual or community is the most significant factor in determining it’s capacity to cope with and withstand the impact of a hazard.
Cultural determinism
The view that cultural factors are significant in determining an individual’s or community’s capacity to cope with the impacts of a hazard. Cultural factors include a person’s values, beliefs and possibly their age and family situation.
Fatalism
An acceptance that hazards are a natural part of living in an area and that losses are inevitable. May be linked to a belief that they are ‘God’s will’.
Prediction
Improvements in technology, such as remote sensing and satellite images, have increased our ability to give advanced warnings of hazardous events. This allows for communities to take action.
Adaption
If we accept that natural events are inevitable, we can adapt/make changes to increase the level of protection and reduce risks. This may include making changes to the built environment
Mitigation
Actions aimed at reducing the seriousness of an event and lessening its impacts.
Management
Modern management techniques involve gathering accurate information, careful analysis and deliberate planning to make the most efficient use of the money and resources available.
Community Risk Sharing
One way of reducing people’s vulnerability. It involves public education and awareness programmes. It may include evacuation procedures and shelters as well as insurance (in richer areas).
Hazard Distribution
The spatial coverage of a hazard. The area affected by a specific hazard. Some events are localised, and some have a much wider effect.
Hazard Frequency
The distribution of a hazard through time. Some are very infrequent, and some are more regular.
Hazard Magnitude
The size of impact of a hazard. This can be given using a scale for example the Richter scale for earthquakes, the Saffir-Simpson scale for tropical storms and the Volcanic Explosivity Index (VEI) for volcanic eruptions.
The Park Model
Also known as the disaster-response curve. It show’s how people’s quality of life is likely to change through the five phases of a disaster.
The Hazard Management Cycle
This represents hazard response as a continuous process. The cycle has four stages: Preparation, Response, Recovery and Mitigation
Core
The densest, hottest part of the planet. Made of rocks rich in iron and nickel. Temperatures can exceed 5000oC. The heat is the result of primordial heat and radiogenic heat.
Primordial heat
Heat left over from the Earth’s formation.
Radiogenic heat
Heat produced by the radioactive decay of isotopes.
Mantle
Surrounds the core. The thickest layer made of silica rocks rich in iron and magnesium. The upper part of the mantle is semi-molten (plastic) and is known as the aesthenosphere. Convection currents occur here.
Crust
Thinnest outer solid layer. Two types of crust, oceanic and continental.
Oceanic crust
Found beneath the world’s oceans. Composed of relatively dense basalt and between 6-10km thick. Formed at spreading mid-ocean ridges at constructive margins.
Continental crust
Forms the continents. Is thicker and older, can be up to 70km thick. Composed of granite. Formed at subduction zones
Lithosphere
The crust and rigid upper mantle.
Aesthenosphere
The semi-molten, plastic upper mantle. The layer is below the lithosphere.
Plate tectonic theory
This theory has evolved over many years. It suggests that the crust is divided into tectonic plates that move due to convection currents in the asthenosphere. This movement creates distinctive features including mid-ocean ridges, ocean trenches and fold mountains, in addition to causing earthquakes and volcanic activity
Alfred Wegener
Published a theory in 1912 suggesting that there was once one supercontinent called Pangea and that over time the landmasses drifted apart until they reached their current positions. His theory was based on a range of evidence, including geological, climatological and biological. He could not explain how continental movement could have taken place.
Mid-Atlantic Ridge
A continuous uplift feature than runs down the centre of the Atlantic Ocean. The central part of the ridge is marked by a central valley. First seen in the 1940s when the ocean floor was first mapped. Since then, mid-oceanic ridges have been found in the other oceans.
Sea floor spreading
Surveys of the ocean floor established that rocks found closest to mid-oceanic ridges were the youngest and rocks nearest the continental landmasses were the oldest. This supported the idea that the sea floors were spreading out from the mid-oceanic ridges where new crust was being formed as magma reached the surface as two oceanic plate moved apart at a constructive margin.
Palaeomagnetism
The rocks that form the ocean floor show stripes of alternating polarity. Lavas that erupt at the mid-oceanic ridges contain iron which aligns to the Earth’s polarity. This becomes fixed when the lava solidifies. The Earth’s magnetic field reverses, on average, 4 to 5 times per million years. These switches are recorded in the rocks of the ocean floor as aa series of ‘magnetic stripes’ with rocks aligned alternatively towards north and south poles. The pattern suggests that ocean crust is spreading out from the mid-ocean boundary.
Convection currents
High temperatures at the Earth’s core help to create continuous convection currents in the aesthenosphere that transfer heat from the core to the Earth’s surface. As the heated magma spreads out underneath the crustal plates it causes them to move due to traction. The magma then cools, becomes denser and sinks downwards again. In recent years the theories of ridge push and slab pull have been added to the theory of convection currents to help explain plate movement.
