Global Hazards

Question 1

What is the crust?

Answer 1

The crust is the outer layer of the Earth which humans reside. It is the thinnest and most dense layer. It varies from 5-70km in depth.

Question 2

What is the mantle?

Answer 2

The mantle is the thickest section of the Earth at approximately 2,900 km. The mantle is made up of semi-molten rock called magma.

Question 3

What is the inner core?

Answer 3

The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.

Question 4

What is the outer core?

Answer 4

The outer core is the layer surrounding the inner core of the earth. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core.

Question 5

What are convection currents?

Answer 5

Convection currents are caused by the heat from the core which heats the mantle, this rising heat goes two separate ways in the mantle (left and right) this causes plates to move.

Question 6

What is slab pull?

Answer 6

Slab pull occurs where older, denser oceanic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulled along behind. Sinking in one place leads to plates moving apart in other places.

Question 7

What is a destructive plate boundary?

Answer 7

A destructive plate margin
usually involves an oceanic plate and a continental plate. The plates move towards one another and this movement can cause earthquakes. As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as
subduction. This happens because the oceanic plate is denser (heavier) than the continental plate. This can form volcanos.
If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a
collision boundary. Earthquakes can occur at collision boundaries.

Question 8

What is a conservative plate boundary?

Answer 8

At a conservative plate margin, the plates move past each other or are side by side moving at different speeds. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake.

Question 9

What is a constructive plate boundary?

Answer 9

At a constructive plate margin the plates move apart from one another. When this happens the magma from the mantle rises up to construct new land in the form of a shield volcano. The movement of the plates over the mantle can cause earthquakes.

Question 10

What is a shallow focus earthquake?

Answer 10

Shallow-focus earthquakes are the most common type, accounting for about 75% of all seismic activity. These earthquakes occur at depths less than 70 kilometres below the Earth’s surface. Shallow focus earthquakes don’t take much time for the energy to get to the epicentre so they can be very destructive.

Question 11

What is a deep-focus earthquake

Answer 11

Deep-focus earthquakes are much rarer than shallow-focus. They are also rarely destructive because it takes a lot longer for the energy to reach the epicentre.

Question 12

How are shield volcanoes formed? What are they like?

Answer 12

Formed at constructive plate boundaries, they are formed by eruptions of thin, runny lava.
Gentle volcano, magma rises and sets to create a dome shaped volcano. It has thin runny lava, frequent but relatively gentle eruptions

Question 13

How are composite volcanoes formed? What are they like?

Answer 13

They occur on destructive plate boundaries
Composite volcanoes are made up of alternating layers of lava and ash (other volcanoes just consist of lava).
The partially melted mantle that rises up is viscous, it contains trapped seawater and hot gasses. This builds up pressure, when it is released, steam and dangerous gasses erupt violently.
The eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow. A pyroclastic flow is a mixture of hot steam, ash, rock and dust.
A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C.

Question 14

What is a hotspot?

Answer 14

Hotspots are places where large plumes of magma rise up through the crust. They are caused by a static source of magma, often away from plate margins. As the plate moves away from the hotspot, a new volcano island will form.

Question 15

Explain the causes of an eruption you have studied (Eyjafjallajökull)

Answer 15

Eyjafjallajökull is on a constructive plate boundary between two oceanic plates; the North-American plate and the Eurasian plate forming the Mid-Atlantic Ridge. This weakness in the crust causes volcanoes to be present
Iceland is also on a hotspot. This means that there is increased volcanic activity.

Question 16

What were the local impacts of the Eyjafjallajökull eruption?

Answer 16

Visibility in the local, rural area, was extremely poor and people had to wear goggles and facemasks. Over 500 farmers and their families had to be evacuated as the roads surrounding the volcano were shut down.
The ash contaminated local water supplies causing farmers to have to bring their livestock indoors.
Finally large floods of water (called jökulhlaups) swept down the side of the volcano destroying bridges and roads.

Question 17

What were the international consequences of the Eyjafjallajökull eruption?

Answer 17

During the eruption there was an 8 day travel ban across much of Eastern/Northern Europe. Around 107,000 flights accounting for 48% of total air traffic and roughly 10 million passengers.
Airlines lost an estimated £1.2bn as they could not fly due to the ash in the atmosphere.
Further to this food supplies that were normally flown to locations could not be transported. 20% of the Kenyan economy is based on the export of vegetables and cut flowers to Europe. Over 50,000 farmers were temporarily unemployed as their produce could not be sold.

Question 18

Explain how areas of low pressure form climate zones; particularly the ITCZ

Answer 18

The ITCZ is a zone of convergence at the equator where the trade winds meet. It is a low pressure belt and migrates with the changing position of the equator. Variation in the location of the ITCZ dramatically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics.

Question 19

Explain how areas of high pressure create climate zones (deserts and polar environments)

Answer 19

The air travels in the upper atmosphere and sinks at approximately 30° north and 30° south of the Equator (this is where the majority of deserts are found) where the Hadley and Ferrel cells meet. When the air sinks it creates an area of high pressure. These high-pressure areas experience very dry and warm conditions resulting in a hot desert climate. This creates a belt of desert regions

Question 20

Why do we have weather extremes?

Answer 20

• Latitude and High Pressure zones
• Rain Shadow
  A rain shadow is a patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather. On one side of the mountain, wet weather systems drop rain and snow. On the other side of the mountain—the rain shadow side—all that precipitation is blocked.
• Monsoon
  A monsoon climate is characterised by a dramatic seasonal change in direction of the prevailing winds of a region which brings a marked change in rainfall.

Question 21

What happens during El Nino?

Answer 21

During El Nino, the trade winds weaken, stop or even reverse in the Western Pacific.
The piled up warmer water around Australia makes its way back eastwards across the Pacific, leading to a 30cm rise in sea level around Peru preventing the usual cold upwelling.
As a result there is more warm water over the coast of Peru leading to rising air and low pressure. The water becomes 6-8c warmer in the eastern Pacific.
Peru would therefore experience more rainfall than normal.
In Australasia, however, the water becomes cooler and there is less air rising resulting in high pressure and stable, dry conditions.

Question 22

What happens during La Nina?

Answer 22

La Nina event may, but does not always, follow an El Nino event. La Nina refers to unusually cold sea temperatures (3-5c colder) found in the Eastern Tropical Pacific. Broadly speaking, the impacts of La Nina are the opposite of El Nino, where Australia would experience droughts during El Nino, there could be increased risk of flooding during La Nina. Likewise, Peru could experience droughts during La Nina. La Nina could also be described as a more exaggerated version of a normal year in the Pacific Ocean. El Nino and La Nina are among the most powerful phenomena on Earth, affecting climate across more than half of the planet. Their consequences can, in fact, be global.

Question 23

Explain how the global circulation of the atmosphere causes extremes in weather conditions in different parts of the world

Answer 23

Point: The global circulation of the atmosphere, driven by uneven heating of the Earth’s surface, plays a crucial role in causing extremes in weather conditions worldwide.

Evidence: At the equator, solar radiation is more intense, leading to warm air rising and creating a low-pressure zone. As the air rises, it cools and condenses, resulting in heavy rainfall and the formation of the Intertropical Convergence Zone (ITCZ). Conversely, at the poles, solar radiation is less intense, causing colder temperatures and high-pressure systems. The temperature contrast between the equator and the poles drives the movement of air masses, creating global wind patterns such as the trade winds, westerlies, and polar easterlies.

Explain: These global wind patterns play a key role in transporting heat and moisture across different regions, thereby influencing weather conditions. For instance, regions near the equator experience consistently warm and wet conditions due to the convergence of air masses and high levels of precipitation associated with the ITCZ. Conversely, areas situated under the descending limbs of the Hadley, Ferrel, and Polar cells, such as deserts and subtropical regions, often experience dry and arid conditions due to descending air, which inhibits cloud formation and precipitation.

Link: Therefore, the global circulation of the atmosphere creates a dynamic system of air movement that leads to variations in weather conditions worldwide.

Question 24

Describe the distribution and the frequency of drought.

Answer 24

Areas most at risk from drought are central and southern Africa, the Middle East, Australia, eastern South America and parts of North America. The distribution of droughts has changed over time. Since 1950, there have been more droughts in Africa, Asia and the Mediterranean and fewer droughts in the Americas and Russia. The frequency of droughts however, has not altered much in that same time period. Some scientists predict that droughts might become more frequent and more severe in the future due to climate change.

Question 25

What were the causes of the UK drought 2010-2012?

Answer 25

Unusual wind patterns brought drier air from the East. This led to a decrease in rainfall

Less rainfall 55% - 95% of usual rainfall received from 2010 to 2012

People in the UK are accustomed to using large quantities of water. 1.7 billion litres of water is used every day in the UK.

Water is wasted through leaking pipes

Prolonged period of time with high pressure

Question 26

What were the environmental impacts of the UK drought 2010-2012?

Answer 26

Dry areas of moorland caught fire easily – wildfires raging (environmental)

Warmer temperatures (environmental)

The soils were dry and baked and the water struggled to infiltrate through the soil. (environmental/economical)

Water shortages made it difficult to find water for crops and livestock. (environmental/economical)

Question 27

What were the economic impacts of the UK drought 2010-2012?

Answer 27

Conditions were difficult for both livestock farmers and growers. Farmers struggled to harvest crops from the dry ground.

Water shortages made it difficult to find water for crops and
livestock. (environmental/economical)

Restrictions in homes – 35 million people were living in drought affected areas. Homeowners were still able to turn on the tap for water. But hosepipe bans were introduced which meant that around 20 million people weren’t allowed to use hosepipes to water their gardens or wash their cars. Less people going to work possibly

Question 28

What were the social impacts of the UK drought 2010-2012

Answer 28

Restrictions in homes – 35 million people were living in drought affected areas. Homeowners were still able to turn on the tap for water. But hosepipe bans were introduced which meant that around 20 million people weren’t allowed to use hosepipes to water their gardens or wash their cars. Less people going to work possibly

Conditions were difficult for both livestock farmers and growers - some were temporarily unemployed

Many homes were without AC or fans. This is because the UK were unprepared for prolonged hot temperatures like these. This lead to Many elderly people getting heat stroke as the temperatures were too hot to bear.

Question 29

What were the short and long term responses to the UK drought 2010-2012

Answer 29

As the seriousness of the drought became clear, water companies took action to keep
water flowing through the pipes of the UK. Permits were granted to allow the water companies to extract water from pipes (short term)

Hosepipe bans were implemented to conserve water that was available. Severn Trent (a large water company) sold up to 30 million litres of water a day to Anglian Water, one of the seven companies that have imposed a hosepipe ban, to help ease the shortage. (short term)

There were campaigns to get ordinary people to use less water in their homes. Even
something as simple as turning off the tap when you brush your teeth which could save you 6 litres of water per minute, or timing your shower. This could have encouraged people in the long term to continue these habits even after the drought cleared. (long and short term)

Question 30

Describe how a Tropical Storm forms

Answer 30

Step 1:
The ocean water must be at least 27°C.

Step 2:
the warm water heats the air above it, causing it to rise. This causes an area of very low pressure.

Step 3:
As the air continues to rise quickly it draws more warm moist air up from above the ocean leading to strong winds.

Step 4:
The rapidly rising warm air spirals upwards, cools, condenses and large cumulonimbus clouds form.

Step 5:
These clouds form the eye wall of the storm and produce heavy rainfall.
In the centre of the storm, cold air sinks forming the eye of the storm - here, conditions are calm and dry.

Step 6: The tropical storm spins due to the coriolis effect.

Question 31

Discuss whether the frequency of Tropical Revolving Storms has changed over time.

Answer 31

Tropical storms are becoming more apparent with climate change. As the earth heats up it is more likely for the temperature of water to exceed 26.5.

Question 32

Describe the distribution of tropical revolving storms

Answer 32

As tropical storms require warm oceans, they are normally found in tropical regions between 5° and 30° north and south of the equator where the water is warmest. This is because the suns rays are more concentrated at the equator. Tropical storms usually form in the late summer when sea temperatures are at their highest. The Pacific Ocean generates the greatest number of tropical storms and cyclones. The most powerful storms, sometimes called super typhoons, occur in the western Pacific. The Indian Ocean is second in the total number of storms, and the Atlantic Ocean ranks third.

Question 33

Describe the causes of your ‘case study hurricane’ (Hurricane Dorian)

Answer 33

One of the place-specific causes of hurricane Dorian was the temperature of the sun. The temperature of the sun’s rays were very hot in summer because the sun’s rays are very concentrated between the Hadley cells and the North of the Equator. The suns rays also lead to warmer ocean temperatures causing moist air to rise, creating a low air pressure zone - which is necessary for the formation of a hurricane. As the sea temperature was high enough, and there were different types of air pressure coming in from the sides, this lead to the formation of hurricane Dorian. Another reason is that the Bahamas is an archipelago, this lead to the hurricane taking more energy from the ocean whilst also hitting land, instead of the hurricane wasting all of its energy, it continued to grow because of the water.

Question 34

Describe the consequences of your ‘case study hurricane’ – Social, economic and environmental (Dorian)

Answer 34

Social: According to the guardian: Undocumented Haitian immigrants may be reluctant to seek government aid to prevent the risk of being penalized and deported. In every country, including the United States, people are scared to come out and register during crisis time, because after the crisis is finished they fear that they probably have enough information on them to go and pick them up and deport them.

Social: According to ‘The Conversation’: Hate-filled social media posts and voice messages shared by Bahamians on Facebook include rumours about “packs” of Haitians roaming flooded areas of the island, looting and robbing abandoned buildings. Commentators called Haitians “thugs” and said those who commit crimes in the wake of Hurricane Dorian should be “shot in the head.” Widely held stereotypes portray Haitians as a burden on the Bahamas’ economy and a strain on its health care, education and social services systems. Many Bahamians even think Haitians have a proclivity for violence.”

Environmental/social: “Over 200 wells were flooded with ocean water, leaving families without safe water for drinking and basic hygiene. With the world now in the grip of the COVID-19 pandemic, the danger of disease spreading from a lack of clean water for hand washing and sanitation is even more clear.”

Environmental: Hurricane Dorian has left oil seeping into the ground on the island of Grand Bahama after the storm blew the tops off five crude-storage tanks on the island.

Economic: The total cost of the disaster was estimated at $3.4bn - with the majority of this as ‘damages’ and the rest as debris clear up and lost revenue. The housing sector suffered the highest damage, while tourism sector bore most of the losses.

Social: An estimated 76,000 people in the Bahamas were left homeless after Dorian rendered parts of some Bahamian islands uninhabitable. 65 people were confirmed to have died. Many houses had to be rebuilt putting a strain on the Bahamian economy.

Question 35

describe the responses to your ‘case study hurricane’ – Long and short term (Dorian)

Answer 35

Short term: The Mercy corps project offered 500 solar-powered lanterns equipped with USB chargers to community members in need and water sanitation systems set up to provide clean water.

Short term: Government: In addition to providing tax relief through duty and VAT exemptions, the Government designated parts of Grand Bahama as Special Economic Recovery Zones (SERZ), which included designating these islands as VAT-free until June 2020

Long term: After hurricane Dorian,the government of
The Bahamas asked the (IDB) to assess the resulting damage, losses and additional costs. The report, completed by the Latin and Southern American branch of the UN, also gave recommendations for further resilience measures.

Long term: The Bahamian government, with assistance from international organizations and donor countries, initiated extensive reconstruction efforts following Hurricane Dorian. For example, the IDB approved a $100 million loan for reconstruction and recovery efforts in the Bahamas, focusing on restoring critical infrastructure such as roads, bridges, schools, and hospitals.

Question 36

What were the short and long term responses to the Eyjafjallajökull eruption?

Answer 36

Short term responses
* Local evacuation of 500 farmers and their families.
* People told to stay inside due to the amount of ash in the air
* Grounded aircraft all over Europe
* Bring livestock in

Long term responses
* Further research into the effect on ash on aircraft.
* Reconstruction of roads, local flood defences were re-established.
* Improved warning systems were developed to predict future eruptions, including greater
monitoring of the surrounding volcanoes (seismometers, thermal cameras and computer
modelling)