Hazards PG U3 Y13

What is the definition for a hazard?

Atmospheric, hydrologic, geologic and wildfire phenomena that have the potential to affect humans, their structures of activities

What is a natural phenomenon?

A physical event that does not effect humans

What is a natural hazard?

A natural phenomenon that occurs in a populated area, causing large numbers of fatalities or property damage

What is an example of human interference causing natural hazards?

Destroying coral reefs removes the shores firs line of defence against ocean currents and storm surges

What are the three categories of hazards?

• geophysical - hazards caused by internal earth processes or tectonic activity or mass movement

• Hydrological - hazards caused by the occurrence, movement and distribution of surface and underground water

• Atmospheric - processes operating in the atmosphere resulting in extreme weather or atmospheric conditions

What are the characteristics of natural hazards?

• clear causes/ origins

• Little or no warning beforehand

• Distinctive effects

• Scale and impact required an emergency response

What does dregg’s model show?

That a natural disaster occurs when a physical hazard and a vulnerable population intersect

What is a natural disaster stated by 2 organisations?

• UN - when over 10 people are killed, over 100 are effected, state of emergency is declared and international assistance is needed

• 1990 Swiss Reinsurance - an event where at least 20 died or over $16 million in damage is caused

What is meant by vulnerability?

Being more susceptible to the effects of the event

Why may some people be more vulnerable to hazards?

• access to healthcare → if the majority of the population is already healthy

• Ages of individuals → older population more vulnerable to injuries

• Access to transport → to leave the area for safety

• Knowledge of hazard occurring → so there is time to plan and prepare reducing deaths and injuries

the risk of disaster grows as…

global hazards and people’s vulnerability increases, whilst their capacity to cope decreases

What does perception mean?

The way someone understands or interprets a hazard, which may affect how they respond to the hazard

What does the model of vulnerability show?

How different factors such as social, geographic, economic and environmental conditions affect people’s susceptibility to hazards and the impact of hazards

What are the 4 types of responses to hazards?

• fatalism - accepting the fact that hazards and their effects are inevitable as it’s part of ‘God’s Will’

• Adaptation - believing that you can prepare for and survive the event from prediction and prevention

• Fear - moving away from the area as they feel vulnerable to an event and don’t feel safe living there

• Domination - believing hazards are predictable and can be better understood with scientific research

What are some influences that may affect response to hazards?

• level of education

• Past experience

• Employment status

• Religion, cultural, ethnic background

• Family and marital status

What is meant by prediction?

Monitoring the risk of the hazard

What is meant by management?

How the hazard is dealt with

What is socio-economic disruption?

The disruption to social lifestyle or economic aspects

What is meant by environmental degredation?

Deteriation of the natural environment

What is the risk management cycle?

4 strategies that can reduce the impacts of effects of the event:

• preparedness - educating people on how to prepare and act before, during and after a hazard

• Response - immediate help saves people and provides resources

• Recovery - rebuilding infrastructure and rehabilitating affected people

• Prevention - reducing the scale of the next disaster by implementing strategies such as hazard resistant infrastructure

What are the positive and negatives of the risk management cycle?

Positive:

• easy to remember

• centred around the 4 Ps (prediction, preparation, protection, prevention)

• Can be applied to other places and different hazards

Negatives:

• too generic and unquantifiable

What is the Park Model (1991)/ Disaster Response Curve?

• describes a sequence of phases following a hazard event

• It refers to the strategies and events taken to bring ‘back to normal’ after a disaster

What are the stages in the Disaster Response Curve?

1. Pre disaster

2. Hazardous event occurs

3. Search rescue and care

4. Relief (outside help)

5. (Sometimes occurs) joy of people who have survived

6. Reconstruction and recovery of area

What are the positives and negatives of the Park Model (1991)

Positives:

• focuses on the three Rs (relief, rehabilitation and reconstruction) that help understanding of recovery after the event

• Useful when comparing hazard events due to their diff curves

Negatives:

• doesn’t account for different levels of economic development or other issues

How old is the earth?

Around 4.5 million years old

What shape is the earth?

A geoid shape → bulges at equator and flatter at poles caused by centrifugal forces generated by the earths rotation

What is the inner core?

• Around 5500 degrees C

• Consists of mostly iron and nickel

What is the outer core?

• Similar temps to inner core

• Made of mainly iron

• Creates electromagnetic field

What is the mantle?

• widest section of earth

• Temps reach 5000 degrees c

• Upper mantle is rigid and solid

• Lower mantle is liquid iron and magnesium

What is the crust?

• thinnest and lightest layer of the earth due to abundance of oxygen, aluminium, silicon etc

• Crust split into 2: continental (sial) and oceanic (sima)

What is the continental crust?

• 30-70km thick

• Over 1500 mill years old

• Composed of granite, silicon, aluminium and oxygen

What is the oceanic crust?

• 6-10km thick

• Less than 200mill years old

• Composed of basalt, silicon, magnesium, oxygen

Why may some places suffer more from earthquakes than others?

1. Infrastructure → better structurally designed areas for earthquakes suffer less

2. Preparedness → regular earthquake drills and knowing how to respond in the event reduces scale of disaster

3. Development levels → LICS have less rigorous building standards meaning they’re unable to cope with the aftermath of an earthquake whereas HICS suffer less human loss but more financial loss from reconstruction

What are convection currents?

• hot magma near the outer core rises through the mantle due to it being less dense

• As the magmas reaches the lithosphere, it cools and becomes more dense

• The magmas reaches sinks back down to the outer core

• This creates large convection currents, causing plate movements

What iS the plate tectonic theory?

Tries to explain how the earth is structured and what it’s made up of

How was the plate tectonics theory formed?

• 1912 → Alfred Wegner proposes continental drift

• 1953 → Marie Tharpe recognises the mid Atlantic ridge spreading

• 1962 → Harry Hess names “Spreading Ridges”

• 1963 → Viens and Matthews carries out magnetic striping on the ocean floor to find rock ages

Who was Alfred Wegner? 1912

• he found evidence for continental drift:

• Pangea → continents used to fit together to form one big one

• Fossil evidence proved this as the mesosaurus (fresh water croc) found in South Africa and Southern South America + was impossible for croc to swim that far in salty sea water

• Limestone was found in the Uk suggesting the Uk was once tropical meaning it used to be further south

Who was Marie Tharpe? 1953

• Mapped the land under the sea using submarine data, showing a rift valley along mid Atlantic ridge

• found that ridges in the ocean were seismically active

• found the mid Atlantic ridge was 1000km wide and made of volcanic rock

Who was Harry Hess? 1962

• studied the age of rocks along Atlantic floor

• Found youngest rocks in the middle and oldest rocks further from ridge

• This shows the ocean floor was spreading outwards from the centre

• This was proven from paleomagnetism (studying the changes in the earths magnetic field over its history to determine the age of the ocean floor in a particular spot)

Who were Vine and Matthews? 1963

• looked at patterns of magnetic stripes on the ocean floor

• Found that the earths magnetic field switches direction overtime from N to S and S to N, meaning iron ions lay acording to which way the direction is

• Found there was a symmetrical pattern of magnetic stripes on either side of mid ocean ridges

who was Tuzo Wilson?

• proposed plates may move over a fixed hotspot in the mantle, forming volcanic island chains e.g Hawaii

• Discovered conservative plate boundary (plates slide past each other without oceanic crust created or destroyed)

How are hotspots formed?

1. Radioactive decay in core generated very hot temps

2. Concentrated decay causes hotspots to form, heating lower mantle and creating localized thermal currents where magma plumes rise vertically

3. The plumes occasionally rise in centre of plates and burn through lithosphere (volcanic activity)

4. As hotspots remain stationary, plates move over it, forming a chain for volcanic islands e.g Hawaii

What happens at a subduction destructive plate margin?

1. Oceanic crust subducts underneath the continental crust as its less dense, creating a zone of melting (Benioff Zone)

2. This melted crust moves up the mantle and creates a composite volcano at the surface

What is an example of a subduction destructive plate margin?

Arenal volcano In Andes Mountains in Peru Chile

What happens at a collision destructive plate margin?

1. Two plates move towards each other, forcing one plate above the other as the other subducts

2. This creates fold mountains where there are depressions called synclines and hills knows as anticlines

What is an example of a collision destructive plate margin?

Himalayan mountains in Nepal

What happens at a conservative plate margin?

1. Two mates move past each other in the same or different direction

2. This causes violent earthquakes to form

3. Focus is the centre of the earthquake in the crust

4. The epicentre in the centre of an earthquake on the surface

What is an example of a conservative plate margin?

San Andreas in California USA

What happens at a constructive plate margin?

• two plates move away from each other

• Magma rises to fill this gap between the two plates

• 1. This creates fissures, shield volcanoes, small earthquakes and ridges in the ocean as lava layers build up

• 2. Or it creates a rift valley where fissures, composite volcanoes and milder earthquakes form

What is an example of constructive plate margins?

East African rift valley

What’s the difference between composite and shield volcanoes?

• Composite volcanoes are more violent

What is seismicity?

The frequency of earthquakes and tsunamis in a region

What is Vulcanicity?

The process where gases and molten rocks are extruded on earths surfaces or intruded on earths crust (volcanoes)

How and where are young fold mountains fold and an example?

How:

• 2 plates collide, forcing sedimentary rock upwards into a series of folds

where:

• Along edge of continents due to large amount of sedimentary rocks here

Example:

• Himalayas Nepal

How and where are rift valleys and an example?

How:

• plates pull apart, causing crust to stretch and fracture leading to blocks of land to drop between fault lines

Where:

• On land or at bottom of ocean due to seafloor spreading

Example:

• lake in Iceland formed from volcanic activity around rift valley here

How and where are ocean ridges and an example?

How:

• 2 tectonic plates move apart causing magma to fill the gap between them

• The magmas cools and solidifies to create new crust

Where:

• constructive plate boundaries on ocean floor

Example:

• Mid Atlantic ridge

How and where are deep sea trenches and an example?

How:

• subduction of a plate below another plate, creating a steep V shaped depression

Where:

• ocean floor

Example :

• Mariana Trench in Pacific Ocean

How and where are island arcs and an example?

How:

• oceanic plate subducting under another, causing magma to rise to surface

Where:

• destructive plate margins

Example:

• Aleutian Islands off coast of Alaska

How and where are volcanoes and an example?

How:

• movement of plates causing magma to rise to the surface and can erupt

Where:

• destructing and constructive plate margins

Example:

• Mount Fuji Japan

How were the Hawaiian islands formed?

1. Conc of radioactive elements in mantle causes hot solid rock to rise to the hotspot

2. Lower pressures at shallower depth causing rock to melt and form magma

3. Magma rises through pacific plate to supply active volcanoes

4. Older islands were located above a stationary hotspot but were carried away due to pacific plate drifting to the north west

How are supervolcanoes formed?

1. Magma chamber in crust grows in size, forcing the ground upwards, creating fissures and hydrothermal features

2. Gas and ash escape through the fissures and into surface cracks (super eruption)

3. The land collapses into the now emptier magma chamber, forming a depression (caldera)