Edexcel IGCSE Geography - Hazardous Environments [Detailed and Accurate]
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The Edexcel IGCSE Geography notes were compiled in line with the specification, consulting textbooks, websites, and studies. These notes take the form of notes, diagrams and summaries.
These notes were used by numerous students, all of whom achieved Grade 8s and 9s at GCSE for Geography. The n...
N.B. These notes should not be misconstrued to be entirely what will be tested, however they have been
compiled in line with the Specification, using resources recognised by the Examination Board.
1
,Table of Contents – Hazardous Environments
3.1 Some places are more hazardous than others
a) Characteristics, distribution and measurement of different types of natural hazards including
tropical cyclones, earthquakes and volcanoes………………………………………………………………………….
b) Causes of tropical cyclone hazards, including ocean temperature, atmospheric pressure, wind shear
and Coriolis force……………………………………………………………………………………………………………………….
a) Causes of volcanic and earthquake hazards, including the role of plate boundaries and hotspots
3.2 Hazards have an impact on people and the environment
c) Reasons why people continue to live in areas at risk from hazard events…………………………………..
d) Some countries are more vulnerable (physically, socially and economically) than others to the
impacts of natural hazards…………………………………………………………………………………………………………
e) The shorter-term and longer-term impacts of one earthquake, one volcano and one tropical
cyclone hazard…………………………………………………………………………………………………………………………
3.3 Earthquakes present a hazard to many people and need to be managed carefully
f) Preparation for earthquakes (warning and evacuation, building design, remote sensing and
geographic information system)……………………………………………………………………………………..
g) Some countries are more vulnerable (physically, socially and economically) than others to the
impact of natural hazards……………………………………………………………………………………………..
h) Longer-term planning (risk assessment, hazard mapping and rebuilding programmes)…………..
Specification
2
, 3.1
(a) Different types of natural hazards
---
Characteristics, distribution and measurement of different types of natural hazards -
Tropical Cyclones
Characteristics
They bring torrential (fast and heavy) rain, thunder, lightning and strong winds
They do not remain where they are formed
They follow the direction of prevailing winds and ocean currents
The track of a tropical cyclone affects how strong it becomes
- The further it travels, the more energy (heat and moisture) it gathers from warm ocean water
- When the cyclone reaches land, its energy supply is cut off meaning that it loses strength and so
begins to gradually disappear by moving slowly
Distribution
Tropical Cyclones generally occur between the Tropic of Cancer and Tropic of Capricorn
They form near large bodies of water, typically the size of an Ocean
Measurement
The Saffir-Simpson Scale is the measurement that is scaled 1-5 based on wind speed and the power
of the storm
- 1. 75-95 MPH – Very dangerous winds will produce some damage
- 2. 96-110 MPH – Extremely dangerous winds will cause extensive damage
- 3. 111-129 MPH – Devastating damage will occur
- 4. 130-156 MPH – Catastrophic damage will occur
- 5. >157 MPH – Catastrophic damage will occur
--
Earthquakes
Characteristics
These are sudden and brief periods of intense shaking of the ground
The centre of the Earthquake underground is the focus
- The shockwaves travel outwards from the focus
The shockwaves are the strongest at the Epicentre, which is the point that is directly above the
focus on the Earth’s surface
The amount of damage is dependant on the depth of focus and the type of rock
- The worst damage occurs where the focus is the closest to the surface and where the rock is soft
Shockwaves liquify soft rock, making it embody the properties of liquid
- This makes the rock lose its load bearing capability
Distribution
These tend to be found on destructive plate boundaries
- They tend to fringe the Pacific Ocean; the Pacific Ring of Fire is where 75% of the active volcanoes
are located
The American Rift Valley is another common region, which is a constructive plate boundary
3
,Measurement
The Richter Scale is used to measure the amount of energy released during the event, calculated
by a seismograph.
- Richter Scale runs from 2.4 or less to over 8.0.
- Richter Scale is logarithmic; every point up the scale represents a 30-times increase in energy
released.
Mercalli Scale
- Mercalli Scale runs from 1-12
- It is based off the observation of people; 2 – not felt, recorded by seismometer; 5 – felt by nearly
everyone; 12 – houses collapse.
--
Volcano
Characteristics
Lava flow – Few lava flow reaches beyond 10km so the likelihood of killing someone is slim, but it
can damage land and buildings.
Ash – This is thrown into the air during eruptions and can be carried by the wind.
- The further away from the volcano, the thicker the ash deposit.
- The ash can blanket everything, causing roofs to collapse due to the weight.
- Air thick with ash causes humans and animals to asphyxiate (suffocate.)
Gas Emissions – Sulphur gas, Carbon Dioxide, and Cyanide are emitted during eruption.
- Since they are dense gases, they remain close to the ground.
Pyroclastic flow – This is the devastating flow of hot gas, ash and rock during explosive volcanic
activity..
- The downwards flow of this mixture can reach speeds of up to 200 kilometres per hour.
Distribution
They tend to be found on destructive plate boundaries.
- They tend to fringe the Pacific Ocean; the Pacific Ring of Fire is where 75% of the active volcanoes
are located
- The American Rift Valley is another common region, which is a constructive plate boundary.
Measurement
The Volcanic Explosivity Index is used to calculate the severity of the volcano. It is calculated
through the volume of pyroclastic flow, volcanic ash and tephra ejected from the volcano.
- The height of the volcanic eruption and the duration of the eruption are also considered.
- The VEI uses a logarithmic scale from 1-8.
- Since the VEI is logarithmic, every scale up is 10% the amount of material ejected.
Mercalli Scale
- Mercalli Scale runs from 1-12
- It is based off the observation of people; 2 – not felt, recorded by seismometer; 5 – felt by nearly
everyone; 12 – houses collapse.
4
,3.1(b) – Causes of tropical cyclone hazards
---
Tropical cyclone hazards -
Causes of tropical cyclone hazards:
Ocean Temperatures -
Cyclones form when there are deep layers of humid, warm air with temperatures of the sea above
26/27 degrees, leading to huge amounts of evaporation taking place.
- In the North American ocean, cyclones form between July and October.
- In the Southern Hemisphere (near Australia), cyclones form between November and April.
--
Atmospheric Pressure –
Cyclones tend to form in areas of very low air pressure.
- Cyclones form at pressures below 950mb.
- These pressures are reached by rising air drawing in warm air from the surroundings towards the
centre of the Storm at high speeds.
--
Wind Shear –
Little to no wind shear is required for the storm to have a better chance at growing and developing
into a tropical cyclone.
- When the cyclone is formed, the wind helps to move the cyclone to increase its size.
--
Coriolis Effect
This is the effect of the Earth’s rotation which causes winds to not blow in a straight line, but rather
rotate around a central, calm eye instead.
- The Coriolis Effect does not occur at the Equator so Cyclones cannot form here.
5
, 3.1(c) – Causes of volcanic and earthquake hazards, including the role of
plate boundaries and hotspots
---
Volcanic and Earthquake Hazards -
Constructive Plate Boundary
At a Constructive Plate Boundary, the plates are moving apart as the convection currents in the mantle
below cannot pass through the solid rock above.
Volcanoes at a constructive plate boundary
When the pressure pulls the Earth apart, magma rises to fill the gaps between the plates.
This continuous process means that the crust eventually splits.
When this occurs, the magma emerges as lava.
- This cools and solidifies to produce a new crust.
- This leads to the formation of a Mid-Oceanic Ridge, like the Mid-Atlantic Ridge.
At this boundary, there are more frequent, but less volcanic eruptions that are explosive.
Earthquakes at a constructive plate boundary
When the plates are being pulled apart, a gap appears between the two plates.
The pressures that are stored within the focus will be suddenly released causing an Earthquake.
The seismic activity causes waves that ripple or make the ground shake.
At this boundary, you can expect more frequent, but less destructive Earthquakes.
Conservative Plate Boundary
A conservative plate boundary is where two plates are sliding past each other.
Volcanoes at a conservative plate boundary
There is no rising magma or subduction, meaning there are no volcanoes at this plate boundary.
Earthquakes at a conservative plate boundary
At this plate boundary, one plate is sliding past the other because they move at different speeds.
The friction prevents smooth movement as pressure builds up over time.
This build-up of pressure will eventually be released as seismic activity, subsequently shaking the
ground.
Earthquakes here can be very strong.
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