Hazards Flashcards
Natural Hazard-What?
A natural hazard is a natural event that is a potential threat to human life or property
Classification of Natural Hazards-Geophysical
A geophysical hazard is a hazard that is driven by the Earth’s own internal energy sources like Plate Tectonics
Classification of Natural Hazards-Atmospheric
Atmospheric hazards are driven by processes that are weather or climate related
Classification of Natural Hazards-Hydrological
A hydrological hazard is a hazard driven by water bodies, normally the ocean
Common Characteristics of Natural Hazards
- Dangerous affect to human life
- High in energy
- Has a rapid or short warning
- Has primary/secondary impacts
- Hazard causes people to adapt and mitigate
Impacts-Primary
Primary impacts are impacts that have an immediate effect on the area
Impacts-Secondary
Secondary impacts are the result of the primary impacts eg: Homelessness caused by destruction of buliding
The Dregg Disaster Model
According to this model, a disaster is when a hazard affects a vulnerable population
Factors that create a vulnerable population
- Lack of/Bad healthcare
- Bad preparation
- Young children
- Elderly Population
- Poor living conditions
- Steep slopes
- Lack of education
- Bad Water/ Lack of clean water
- Poor buliding quality
- Poor emergency services
- Less Income Country-Less money
Vulnerability-What
How susceptible a population is to the damage caused by a hazard
Perceptions of Hazards-Wealth
Richer people can move away from hazard affected areas, or build home to withstand hazards-Smaller risk for rich, High risk for Poor
Perception of Hazards-Religion
Some people adopt a fatalistic view towards hazards-Less risk for them
Perception of Hazards-Education
Those who are educated about the hazards have a better understanding of them, they can try to reduce the damage caused-Less risk for them
Perception of Hazards-Past Experience
Those who lived in hazard prone areas are more experienced-Less risk for them
Perception of Hazards-Personality
Some people do not fear them, they find them exciting-Less risk for them
Risk Perception-What
The subjective judgement that people make about the characteristics and severity of a risk
Risk-What?
The probability of a hazard event causing harmful consequences
Fatalism-What?
People accept that hazards are a natural occurrence. Loses are inevitable and people remain where they are. “God’s Will”
Adaption-What?
People see that they can prepare for the event so they will survive
Fear-What?
People feel so vulnerable to an event that they move away to areas with no hazards
Factors that increase risk perceptions
- No control over hazard
- Many deaths
- No understanding of Hazard
- Lack of awareness
- Large Scale
Factors that decrease Risk Perception
- Controllable Hazard
- Few deaths
- Understanding of Hazard
- Not being aware of hazard-“Ignorance is Bliss”
- Small scale impacts
- “It will never happen to me” attitude
Responses to a hazard
- Prevention of hazard or reduce the magnitude of the hazard
- Mitigation of the impacts of the hazard
- Government intervention
- Do nothing-Fatalism
The Hazard Management Cycle
Once a hazard happens, the authorities respond to it. Then, the area is reconstructed. Mitigation, which reduces the severity of the hazard is next, which increases the areas preparedness for a disaster. Then, a disaster strikes and the cycle begins again
The Hazard Management Cycle-Mitigation
Actions aimed at reducing the severity of an event and lessening the impacts. Examples of mitigation are: buliding earthquake proof bulidings or educating people on what to do during a hazard. Mitigation can occur before or after the hazard event
The Hazard Mangement Cycle-Preparedness
Planning what to do during a hazard and how to respond to it. Examples:Warning systems, a risk management plan
The Hazard Mangement Cycle-Response
How people react during and immediately after the hazard event. Examples include hiding in a safe place, rescuing people who are trapped
The Hazard Management Cycle-Recovery
Getting the area back to a state of normality. Examples include: Rebuilding houses and restoring the key services in the area
The Hazard Mangement Cycle-Why a cycle?
It is a cycle as hazard events keep happening. Preparation and mitigation is a constant process
The Park Model-Pre Disaster
Before the hazard event, all is normal
The Park Model-Disruption
During and directly after the event, there is destruction of property and loss of life, before the people begin to respond
The Park Model-Relief
The immediate local and possibly global response in the form of aid,expertise and search and rescue
The Park Model-Rehabilitation
The resolving of longer term problems, including temporary housing solutions and the restoration of services
The Park Model-Reconstruction
The rebuilding of permanent houses and infrastructure
The Park Model-Reconstruction-Same
If buildings are the same as they were pre event, the area returns to normal
The Park Model-Reconstruction-Higher
If the buildings are to an improved standard than pre event, the area improves and the vulnerability to hazards decrease
Plate Tectonics-Core
The area of the centre of the Earth. It is the hottest part and is divided into the inner core and the outer core
Plate Tectonics-Core-Inner Core
A solid ball that is 1300KM thick and has a temperature of 7200degrees Celsius. It is made of iron and nickel
Plate Tectonics-Core-Outer Core
A semi molten area that is 2200KM thick. It contains lots of iron and nickel
Plate Tectonics-Mantle
The mantel is above the core, and is made out of silicate rocks.
Plate Tectonics-Crust
The outer layer of the Earth. There are two types of crust
Plate Tectonics-Types of Crust-Continental
The thicker and less dense type of crust
Plate Tectonics-Types of Crust-Oceanic
The thinner and more dense type of crust
Plate Tectonics-Spheres-Lithosphere
This sphere consists of the crust and the upper part of the mantle
Plate Tectonics-Spheres-Astenosphere
A plastic layer below the lithosphere. The tectonic plates float on the lithosphere
Plate Tectonics-Spheres-Mesosphere
The remaining part of the mantle which connects to the crust
Plate Tectonics-Moho
The line dividing the upper and lower mantle levels
Movement of Tectonic Plates-Convection Currents
The mantle is hottest close to the core, so lower parts of the asthenosphere warm up,become less dense, and rise. As they get to the top of the asthenosphere, they cool down and sink. These movements are convection currents. They create drag on the base of the plate, causing them to move
Movement of Tectonic Plates-Slab Pull
At a destructive plate margin,the denser crust is forced under the less dense crust. The sinking of the plate edges pull the rest of the plate,causing it to move
Movement of tectonic plates-Ridge Push
At constructive plate margins,magma rises to the surface and creates new crust with a slope. The crust cools and becomes denser,with causes the plates to move apart due to pressure. This process is also known as gravitational sliding
Movement of Tectonic Plates-Sea Floor Spreading
As tectonic plates move apart,magma rises to fill the gap, cools and creates new crust. This new crust is dragged apart and more crust is formed between it. This causes the sea floor to get wider
Plate Boundaries-Constructive
A constructive boundary is when two plates seperate
Plate Boundaries-Destructive
Causes when two plates collide with each other
Plate Boundaries-Landforms-Constructive-Mid Ocean Ridge
A mid ocean ridge is caused by sea floor spreading. Mid ocean ridges can also create transform faults,which cut across the ridges and occur a right angles to the plate boundary. Volcanic eruptions along the fault can create submarine volcanos,which can grow to above sea levels
Plate Boundaries-Landforms-Constructive-Rift Valley
Formed when the lithosphere stretches,causing parallel faults. The land between the faults collapses into deep wide valleys,separated blocks of land called Horsts. Example:Great African Rift Valley
Plate Boundaries-Landforms-Destructive-Oceanic and Continental-Deep Ocean Trench
The oceanic plates subducts under the continental plate as it is denser. The point of collision is when the oceanic plate bends and forms a deep ocean trench.
Plate Boundaries-Landforms-Destructive-Oceanic and Continental-Fold Mountains
The continental plate is uplifting,compressed,buckled and folded to create fold mountains eg:The Andes
Plate Boundaries-Landforms-Destructive-Oceanic and Continental-Magma Creation
The decending oceanic plate starts to melt in the Benioff Zone. This process causes magma to be created
Plate Boundaries-Landforms-Destructive-Oceanic and Oceanic-Deep Ocean Trench
When two organic plate collide, the faster or denser plate subducts beneath the other. This creates a deep ocean trench
Plate Boundaries-Landforms-Destructive-Oceanic and Oceanic-Island Arcs
The collision of plate also causes melting at the benioff zone. This magma rises to create submarine volcanoes, which can grow into island arcs
Plate Boundaries-Landforms-Destructive-Continental and Continental-Fold Mountains
The collision of the plates does not cause subduction. The plates become uplifted and buckled to form fold mountains
Plate Boundaries-Landforms-Conservative
There are no landforms formed on conservative plate boundaries
Magma plumes-What?
A magma plume is a vertical column of extra hot magma that rises up from the mantle
Magma Plumes and the formation of Volcanoes
Volcanoes form above magma plumes. The magma plume remains stationary,the crust moves above it. Volcanoes form in the part of the crust that is above the plume. As the crusts move, a chain of volcanoes is formed,like the volcanic islands of Hawaii
Volcanoes-Viscosity
The thickness of lava
Volcanos-Types of Lava-Basalt
Lava that has 48%-52% viscosity
Volcanoes-Types of Lava-Andesite
Lava that has 52%-63% viscosity
Volcanoes-Types of Lava-Dacite
Lava that has 63%-68% viscosity
Volcanoes-Types of Lava-Rhyolite
Lava that has 68%-77% viscosity
Why is rhyolite lava the deadliest
It sticks to the top of the volcano and builds up pressure and eventually erupts at a high magnitude
Types of Volcanoes-Fissure
Have very liquid lava flows,wide spread, lava is emitted from fractures. Example:River Plateau in Colombia
Types of Volcanoes-Shield
Liquid lava is emitted from central vent. Large in size. Example:Hawaiian Volcanoes
Types of Volcanoes-Cinder Cone
Explosive liquid lava,small, emitted from a central valve. Can become shield volcano. Example:Mount Taylor
Types of Volcanoes-Composite
More viscous lava emitted from a central vent. Example:Mount St Helens
Types of Volcanoes-Volcanic Dome
Very viscous lava,commonly occurs adjacent to craters of composite volcanoes. Example:Mount Lassen
Types of Volcanoes-Caldera
Very large composite volcanoes that collapsed after a explosive period. Example:Yellowstone
Location of Volcanoes
Most volcanoes occur near constructive and destructive plate margins. A small number are formed near magma plumes
Volcanic Eruptions-Constructive Boundaries
Basalt lava is formed here. Eruptions are frequent and long lasting,but not violent. If
Volcanic Eruptions-Destructive Boundaries
Andesitic and rhyolitic lava is formed here. Eruptions are intermittent and short,but violent as viscous lava blocks vents,causes pressure to build, which can be reduced by a violent eruption
Volcanoes-Magnitude
Volcanic events range is size. Magnitude is measured using the Volcanic Explosively Index, which grades companies based on the amount of material ejected and how high the material is blasted
Volcanoes-Frequency
How often an eruption occurs. Less frequent eruptions are normally larger in magnitude
Volcanoes-Randomness vs Regularly
Some erupt at regular intervals, while others erupt at random intervals
What determines eruption type-Crystals
Crystals in magma makes it more viscous. Highly crystallized magma means it is more likely to explode
What determines eruption type-Gases
If gas cannot escape highly viscous magma, it creates explosions
What determines eruption type-Temperature
Low temperature magma flows easily and is more likely to erupt explosively
Types of Eruption-Hawaiian
Basatic lava flows gently from a central vent
Types of eruption-Icelandic
Basaltic lava flows gently from fissures
Types of Eruption-Strombolian
Thicker basaltic lava occasionally flows. Frequent explosive eruptions of tephra and steam
Type of Eruptions-Vulcanian
Thicker basltic,andestic and rhyolitic lava flows. Less frequent but violent eruptions of gas,ash and tephra
Types of Eruptions-Vesuvian
Thick basaltic,andesitic and rhyolitic lava flows. Very violent gas explosions blast ash high into the sky, following long period of inactivity
Types of Eruptions-Peléean
Andesitic and rhyolitic lava flows. Very violent eruptions of nuées ardentes
Types of Eruptions-Plinian
Rhyolitic lava flows. Exceptionally violent eruptions of gas,ash and pumice. Torrential rainstorms causes devastating lahars
Volcanic Hazards-Pyroclastic Flow
A mixture of super heated gas,ash and volcanic rock that flows down the side of the volcano. It travels quickly,can can cause widespread death and destruction
Volcanic Hazards-Lava Flows
Lava flow from a vent down the side of the volcano. Speed and distance travelled depends of viscosity. Low viscosity lava can travel faster than high viscosity. Lava flows destroy everything in their path, but as they are slow,allow time for people to evacuate
Volcanic Hazards-Volcanic Gases
Lava contains carbon dioxide and sulfur dioxide which go into the atmosphere during a eruption. These gases can be harmful to life
Volcanic Hazards-Tephra
Material that has been ejected from the volcano. Materials can be of many sizes and can travel thousand of kilometres from the volcano. Large pieces can damage buildings and kill people,smaller pieces can damage vegetation
Volcanic Hazards-Lahars
A mixture of volcanic material and water mixes. These flow very quickly and travel far. Lahars can bury or destroy habitats,and buildings
Volcanic Hazards-Acid Rain
The reaction of volcanic gases and water vapour from the atmosphere. This falls as acid rain. This can damage ecosystems and cause stone and metal to deteriorate
Volcanic Hazards-Social Impacts
- People killed
- Buildings and infrastructure destroyed
- Fires from pyroclastic and lava flows destroy buildings
- Deaths by mudflow and flooding
Volcanic Hazards-Environmental Impacts
- Destruction of ecosystems
- Acidification of aquatic ecosystems
- Acid rain removes nutrients from soil
- Enhanced Greenhouse Effect and Global Warming
- Reduction of Earths temperature
Volcanic Hazards-Economic Impacts
- Business destroyed-No jobs
- Expensive to repair buliding damage
- Eruption can create a form of tourism
Volcanic Hazards-Political Impacts
- Agriculture damage causes food shortages-Creates unrest
- Government spends money on repairing buliding rather than improving services-Slows down development
Prediction of Volcanic Eruptions-Monitoring-Seismic Activity
Microquakes indicate rising magma cracking overlaying rocks
Prediction of Volcanic Eruptions-Monitoring-Ground Deformations
Bulging of ground caused by rising magma
Prediction of Volcanic Eruptions-Monitoring-Upwards movement of iron rich magma
Changing magnetism means magma levels or rising