1C - Hazards Flashcards
Hazard
a potential threat to human life and property caused by an event.
Degg’s Model
Shows the interaction between hazards, disaster and human vulnerability
What are the 3 major types of Geographical hazard?
Geophysical, Atmospheric, Hydrological
What 5 factors affect hazard perception?
Wealth (Wealthier people may perceive a hazard to be smaller as they are less vulnerable. but they also have more to lose so might see it as a greater risk),
Experience (Someone who has experienced more hazards may be more likely to understand the full effects of a hazard),
Education (A person who is more educated about hazards may understand their full effects on people and how devastating they can be and have been in the past)
Religion and beliefs (Some may view hazards as put there by God for a reason, or being part of the natural cycle of life, so may not perceive them to be negative)
Mobility (Those who have limited access to escape a hazard may perceive hazards to be greater threats than they are.)
What are the human active responses to hazards?
Prediction, Adaptation, Mitigation, Management, Risk Sharing
What is the human passive response to hazards?
Fatalism
What aspect of hazards affects human responses?
Incidence, Distribution, intensity, magnitude, level of development
How does incidence affect human responses to hazards?
Frequency of a hazard.
This is not affected by the strength of a hazard; it is just how often a hazard occurs.
Low incidence hazards may be harder to predict and have less management strategies put in place, meaning the hazard could be more catastrophic when it does eventually occur.
Also, low incidence hazards are usually (but not always) more intense than high incidence hazards.
How does distribution affect human responses to hazards?
Where hazards 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.
How does intensity affect human responses to hazards?
The power of a hazard i.e. how strong it is and how damaging the effects are
High magnitude, high intensity hazards will have worse effects, meaning they will require more management, e.g. more mitigation strategies will be needed to lessen the effects and ensure a relatively normal life can be carried out after the hazard.
Intensity is the effects on the person, and can change dependent on the distance from the hazard or the management strategies combating high magnitude risks.
How does magnitude affect human responses to hazards?
The size of the hazard, usually this is how a hazard’s intensity is measured
High magnitude, high intensity hazards will have worse effects, meaning they will require more management, e.g. more mitigation strategies will be needed to lessen the effects and ensure a relatively normal life can be carried out after the hazard.
Magnitude and intensity are not interchangeable terms
The magnitude is usually definable and can be a number - this does not change.
How does level of development affect human responses to hazards?
Economic development will affect how a place can respond to a hazard, so a hazard of the same magnitude may have very different effects in two places of contrasting levels of development.
an area with a lower level of development is less likely to have effective mitigation strategies as these are costly
However, there are many high income countries that are not as prepared for natural hazards as they should be, meaning they lack the management strategies for an event
Structure of the Earth
inner core, outer core, mantle (asthenosphere, lithosphere) crust
Inner core
A dense sphere of solid iron and nickel at the centre of Earth
Very hot due to pressure and radioactive decay (contains elements such as uranium that give off heat when they decompose)
This heat is responsible for Earth’s internal energy, and it spreads throughout
Outer core
Semi-molten
Iron/nickel
Mantle
Mainly solid rock, and the rocks are high in silicon.
However, the very top layer of the mantle is semi-molten magma, which is known as the asthenosphere.
The lithosphere rests on top.
Asthenosphere
The soft layer of the mantle on which the lithosphere floats.
Semi-molten layer constantly moves due to flows of heat called convection currents. Movements are powered by heat from core.
Evidence for tectonic movement
Continental fit, Mountain ranges, Fossils, use of modern technology
Continental fit
Wegener used evidence like the coast lines appearing to match as evidence of continental drift
Disputed by scientists at the time as they mentioned that coastlines were formed through processes of erosion and deposition
using modern day technology we are able to see that although the coastlines of the continents might not fit perfectly, the deeper crusts around them that don’t experience erosion and deposition do
Mountain ranges (evidence for tectonic movement)
The mountain ranges and rock sequences on opposite sides of the Atlantic also contain a huge number of similarities.
The Caledonian Mountains can be traced from North America through Greenland, Ireland, Scotland and Scandinavia.
These mountains are all of the same age, structure and rock type meaning they must have been part of the same mountain range at some point hundreds of millions of years ago.
Fossils (evidence for tectonic movement)
Glossopteris Flora fossils have been found on all Gondwana continents and the seeds are too large to be carried by wind - must have been carried by land animals.
Present day climates of these continents are too diverse to all support life of this plant.
Use of modern technology
Paleomagnetism, is the remnant magnetism in ancient rock which record the direction and intensity of the Earth’s magnetic field at the time of the rock’s formation
Is evidence of sea floor spreading
As new rock is formed and cools, the magnetic grains within the rock align with the magnetic poles.
Our poles (North and South) switch periodically.
Each time these switch the new rocks being formed at plate boundaries align in the opposite direction to the older rock.
On the ocean floor either side of constructive plate boundaries, Geologists observed that there are symmetrical bands of rock with alternating bands of magnetic polarity.
Different types of plate boundary
Destructive, Constructive, Conservative
Destructive plate boundary landforms
Ocean trench, fold mountains, composite volcanoes, island arcs (Oceanic-oceanic)
Constructive plate boundary landforms
rift valleys, shield volcanoes
ridge push and slab pull
the process in which new material at a ridge or rift pushes older material aside, moving the tectonic plates away from the ridge
Hotspots
Hotspots are areas of volcanic activity that are not related to plate boundaries.
What are the 8 volcanic hazards?
lava flows, volcanic ash, pyroclastic flows, mudflows/lahars, glacial floods, tephra, toxic gases, acid rain
lava flow
lava can flow quickly or slowly depending on its viscosity.
Silica makes lava viscous and slow, which is common in explosive eruptions.
lahars (mudflows)
Large amounts of material that become saturated with water and move downslope.
Caused by a number of reasons, usually by melting ice at high latitudes
Glacial floods
When temperatures are high from magma, glaciers or ice sheets at high temperatures quickly melt and a large amount of water is discharged
Tephra
Any type of rock that is ejected by a volcano
Toxic gases
Released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier
Acid rain
Caused when gases such as sulfur dioxide are released into the atmosphere
pyroclastic flow
Clouds of burning hot ash and gas that collapses down a volcano at high speeds. Average speeds of around 60 mph but can reach 430 mph.
Ring of Fire
A major belt of volcanoes that rims the Pacific Ocean
Vulcanicity (magnitude)
Vulcanicity is measured using the Volcanic Explosivity Index(VEI).
The more powerful, the more explosive.
The scale is logarithmic from VEI 2 and onwards.
Multiple features are considered when calculating the VEI, including how much tephra is erupted, how long it lasts, how high the tephra is ejected etc.
Intense high magnitude eruptions are explosive whereas calmer, lower magnitude eruptions are effusive.
Frequency of Eruption
Frequency of eruptions varies per volcano.
Volcanoes are classed as either active, dormant or extinct.
An estimated 50-60 volcanoes erupt each month, meaning volcanic eruptions are always frequent (and some volcanoes erupt constantly).
Usually, a higher frequency eruption means the eruptions are effusive whereas low frequency means the eruptions are explosive.
Regularity of eruptions
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
