Hazards Flashcards
What is a natural hazard?
A natural even or process which affects people, causing loss or injury economic damage etc
What does a natural event need to do to become a natural hazard?
It must affect and involve people, a cyclone in the middle of the pacific that doesn’t affect anyone will remain a natural event
What are the two main types of natural hazard?
Geophysical hazards
Hydro meteorological hazards
What are geophysical hazards?
Hazards that are either caused by inner earth activities or tectonic activities
What are some examples of geophysical hazards?
Volcanoes
Earthquakes
tsunamis
What are examples of geomorphological hazards?
(Hazards involving mass movement)
Landslides
Rockfalls
Rockslides
What are hydrometeorlogical hazards?
Hazards driven by water bodies and the associated weather patterns
What are some examples of hydrometeorlogical hazards?
Blizzards
Droughts
Tropical storms
Hailstorm
Thunderstorms
Floods
Bush fires
Mudflows
Extreme temperaturs
What are the six main reasons people live in areas with natural hazards?
Unpredictability
Lack of alternatives
Russian roulette
Cost vs benefit
Changing levels of risk
Fatalism
Why does unpredictability mean some people live in disaster related areas?
It’s not always known when or where an event will take place and it’s difficult to know the magnitude do it
Human activity and physical changes can increase chances and magnitudes of hazards
Why does lack of alternatives mean some people live in disaster related areas?
Difficult to uproot and move to another location for many, giving up land and employment may be tough
Often the most vulnerable are the poor who are forced to live on fertile volcanic lands or flood plains to survive economically
Why does changing level of risk mean some people live in disaster related areas?
Deforestation and other human activity’s can make areas previously safe at risk, as well as the effects of global warming
Why does a Russian roulette attitude mean some people live in disaster related areas?
Many optimists turn a blind eye believe that disasters are acts of god and will not hurt them
Many look at statistics that show people are more at risk from car accidents or influenza than natural hazards
Many also believe if a high magnitude event occurs they will be safe for a number of years but this is not always true
Why do cost vs benefit mean some people live in disaster related areas?
Many hazardous areas offer advantages that others do not
-e.g fertile flood plains
-rich volcanic soils
-beautiful mountainous landscapes
-volcanoes forming tourist opportunities
What is fatalism?
The belief that hazards are natural events people have little control of, and that losses must be accepted
Many think disruption of natural process will destroy nature
What is prediction and how can it reduce impacts of hazards?
As technology improved there are not, sophisticated methods of predicting hazards such as remote sensing and seismic monitoring. Advances in communication can also reduce the effect of hazards through putting warning systems in place when disaster may strike
What is adaption?
Adaption involved living with and changing our behaviour to reduce the severity of natural hazards, this is sometimes cost effective and the most realistic option for most people
What are the four stages of the hazard management cycle?
Mitigation ->
Preparedness ->
Response ->
Recovery
What is mitigation in the hazard management cycle?
This is the first stage of the hazards management cycle that are actions aimed at reducing the severity of future hazards examples include :
Improved building design
Barriers
Long term natural protection like coral reefs (which are the most desirable methods of mitigation)
What is preparedness in the hazard management cycle?
The second stage of the cycle, it involves improving public education and public awareness - it adjusts human behaviour to help minimise the impacts of a hazard. Knowing what to do in the aftermath of an event speeds up recovery
What is response in the hazard management cycle?
The third stage of the hazard management cycle, involves the effectiveness of the management plan put in place to save lives in the result of a hazard
What is recovery in the hazard management cycle?
The final stage of the hazard management cycle, it involves restoring the affected area to normality
What model depicts the typical response to a hazard?
The park model of human response to hazard
What are the 3 phases of the Park management cycle?
Relief
Rehabilitation
Reconstruction
What is the relief phase of the park model and how long after the hazard event is it?
the immediate local and global response in the form of aid, search and rescue and expertise, it usually takes place within hours/days
What is the Rehabilitation phase of the park model and how long after the hazard event is it?
In this phase, services and infrastructure are restored to allow the reconstruction phase to begin, it usually lasts days to months and sometimes years, depending on the magnitude of the hazard.
What is the reconstruction phase of the Park model?
Restoring the same, or better quality of life as before the event took place, this would likely include increased mitigation capabilities to reduce the impact a similar disaster would happen in the future.
How can a disaster affect QoL in the long run (sometimes)?
It can sometimes lead to an improved quality of life as capacity to cope will increase.
What is the true shape of the earth and why?
Earth is a geoid that bulges around the equator and flattens at the poles, because centrifugal forces generated by the earth’s rotation pushing the semi molten material outwards.
What is the basic structure of the earth?
Inner core (1200km)
Outer core (2250km)
Mantle (2900km)
Crust (5-70km)
What are the characteristics of the inner core?
-Solid ball of iron/nickel
-Very hot due to pressure and radioactive decay (contains
elements such as uranium)
-This heat is responsible for Earth’s internal energy, and it
spreads throughout
- The internal heat generated in the core generates convection currents which spread slowly in the Asthenosphere.
What is Primeval heat?
Primeval heat = Heat generated in the core that is retained from when the earth was a ball of gas and dust.
What is Radioactivity in the context of the earths core heat?
The greatest source of internal heat that originates from the natural radioactive decay of Uranium, Thorium and Potassium to create a continues but slowing decay of heat.
What are the Characteristics of the mantle?
-Mainly solid, rocks high in silicon
-The top of the mantle is the asthenosphere
-The deeper down in the mantle you go, the denser it becomes
-2900km thick
What are the characteristics of the outer core?
-Semi-molten
-Iron/nickel
What is the asthenosphere?
The upper layer of the earths mantle, below the lithosphere, it can move very slowly, moving the Lithosphere on top
What is the Lithosphere?
the rigid outer part of the earth, consisting of the crust and upper mantle, it is the zone where tectonic plates are formed.
How do convection currents form?
Hot rock that is heated by the earths core rises,
Nearer the surface the rock is spread in two opposite directions,
The rock begins to lose heat as it nears the surface,
The cooler rock then sinks back down,
This causes the earths crust to slowly be dragged apart, causing continental drift and moving tectonic plates.
What are the two types of crust?
Oceanic and continental crust.
What is the oceanic crust and what is it made up of?
It is an occasionally broken up layer of Basaltic rocks known as SIMA (as they are made up of Silicon and Aluminium)
What is the continental crust and what is it made up of?
Bodies of Mainly Granite rocks known as SIAL (as they are made up of Silicon and Aluminium)
What is Sial?
The upper layer of the earths crust and forms the continental land masses
What is Sima?
Sima is the lower layer of the earths crust and its found beneath the oceans.
What is thicker the Sial or Sima layer?
Sial (continental) is thicker than Sima (Oceanic)
What is denser Sima or Sial?
Sima is denser (like how oceanic plates are denser and subduct)
What is gravitational sliding?
The process of gravity affecting how tectonic plates move, two types made up of slab pull and ridge push (it explains why tectonic plates move, as convection currents alone aren’t strong enough to do this)
What is ridge push?
The slope created when plates move apart
has gravity acting upon it as it is at a higher
elevation. Gravity pushes the plates further
away, widening the gap
What is slab pull?
When a plate subducts, the plate sinking into
the mantle pulls the rest of the plate (slab)
with it, causing further subduction.
What are the 3 types of plate boundaries?
Destructive
Constructive
conservative
What is a destructive plate margin?
When two plate boundaries collide head on.
What is a constructive plate boundary?
When plates diverge apart
What is a conservative plate boundary?
When plates silde past each other
What happens when an oceanic plate collides with a continental plate on a plate margin?
Continental and oceanic:
● Denser oceanic plate subducts below
the continental.
● The plate subducting leaves a deep
ocean trench.
● Built up pressure from the melting
plate cause explosive volcanoes
bursting through the continental plate
what happens when two oceanic plates collide on a destructive plate margin?
Continental and oceanic:
● Denser oceanic plate subducts below
the continental.
● The plate subducting leaves a deep
ocean trench.
● Built up pressure from the melting
plate cause explosive volcanoes
bursting through the continental plate
What happens when two continental plates collide on a destructive margin?
● Both plates are not as dense as
oceanic so lots of pressure builds.
● Ancient oceanic crust is subducted
slightly, but there is no subduction of
continental crust.
● Pile up of continental crust on top of
lithosphere due to pressure between
plates.
● Fold mountains formed from piles of
continental crust
What happens when two oceanic plates diverge?
● Magma rises in between the gap left
by the two plates separating, forming
new land when it cools.
● Less explosive underwater volcanoes
formed as magma rises.
● New land forming on the ocean floor by
lava filling the gaps is known as sea
floor spreading (as the floor spreads
and gets wider).
What happens when two continental plates diverge?
● Any land in the middle of the separation
is forced apart, causing a rift valley.
● Volcanoes form where the magma
rises.
● Eventually the gap will most likely fill
with water and separate completely
from the main island.
What happens at a conservative plate boundary?
Between any crust, the parallel plates move in
different directions or at different speeds.
No plates are destroyed so no landforms are
created, but the build-up of friction and its sudden release of energy can lead to earthquakes.
What are the three different types of earthquake?
Shallow focus
Intermediate
Deep focus
How deep is the focus of each earthquake?
Shallow focus (0-70km deep)
Intermediate (70 - 300km deep)
Deep focus (300 - 700km deep)
What are magma plumes?
If radioactive decay within the earths core is concentrated, hotspots will form around the core, these hotspots created localised thermal currents where plumes of exceptionally hot lava rise. AS the hotspot remains stationary, the movement of tectonic plates above it results in the formation of an island chain of active volcanoes that become extinct as the plates move away from the hotspot.
What key factor does the destructiveness of a volcano depend on?
The volcanoes’ viscosity (runniness)
What is the difference between high and low viscosity?
Low viscosity = Runny magma = creates a shallow sided volcano
High viscosity = Thich sticky magma = creates a steep sided volcano
More viscous = deadlier volcano, as lava is more thick and prone to blockage, building up pressure
What three things affect viscosity?
Temperature
Silica content (silicon dioxide)
Volume of dissolved gases
How does temperature affect the danger of a volcano?
The hotter the temperature, the less viscous and more runny a volcano becomes, the magma is very hot, runny and buoyant and as a result don’t block the vent, making them less deadly the higher the temperature is.
How does Silica content affect the danger of a volcano?
The higher the Silica content the thicker the magma (and more dangerous the volcano as it blocks vent)
Liquid rocks with high silica content are colder and therefore are more very viscous, so they block up the main vent, which can trap gasses which produce violent explosions.
How does the volume of dissolved gasses affect the danger of a volcano?
The higher the dissolved gas content, the less viscous the magma is, meaning higher volume of dissolved gasses in magma, making it more runny, making explosions less violent
What is the troposhere?
The lowest layer of Earths atmosphere
What are the three types of magma in ascending order of silica content
Basaltic
Andesitic
Rhyolitic
What are the Characteristics of basaltic magma?
- Below 52% silica content (low viscosity and runny)
- High temperature (more dissolved gasses and more runny)
- Easily releases gasses so less violent eruptions
- Runny lava means low cones and plumes of gasses that are unlikely to breach the troposphere
- lava spreads far from volcano so a wide based, cone volcano is formed.
What are the characteristics of andesitic magma?
- Between 52-68% Silica content
- High eruption columns spread gasses far as it penetrates the troposphere
- eruption column can often collapse causing pyroclastic flows
What are the Characteristics of Rhyolitic magma?
- Above 69% silica content
- high silica content means thick magma, forming a viscous thick magma that cools and blocks the main vent, plugging it and trapping gasses so there is a large build up until they are released potentially through a secondary vent
- produces violent and dangerous eruptions due to their high viscosity
How is Basaltic magma formed?
Basaltic magma are formed by the melting of oceanic crust and the mantle so occur at constructive plate margin.
How is Andesitic magma formed?
Andesitic magma is formed when rising basaltic magma moves with continental crust before it reaches the surface - increases silica content, it is largely formed a t subduction zones
How is rhyolitic magma formed?
Rhyolitic magmas with a high silica content are formed when continental crust melts and so form at plate boundaries involving 2 continental crusts.
What are the 5 primary impacts of a volcanic hazard?
Ash
Lava Flow
Pyroclastic flows (nueese ardentes)
Tephra
Gas
What are the 5 secondary impacts of a volcanic hazard?
Acid rain
Climate change
Flooding (Jokulhlap)
Tsunami
Lahar
What is Tephra?
Tephra is a fragmental metal produced by a volcanic eruption, no matter how big or how the volcano was formed. these fragments are airborne and they fall and rmain as Tephra, unless they are hot enough to become Pyroclastic flows
what are the different forms and sizes of Tephra?
Ash (particles smaller than 2mm in diameter)
Lapilli(between 2 and 64mm in diameter)
Volcanic bombs (anything larger than 64mm in diameter)
What are Lava flows an example?
Lava flows are large deposits of lava that flow down the side of a volcano during a n eruption, an example of this is the lava flow that occurred on the canary island of la Palma