tectonic hazards-g2

Question 1

What are tectonic plates?

Answer 1

The earth’s crust is divided into slabs called tectonic plates.

Question 2

What are the two types of crust?

Answer 2

Oceanic and continental crust

Question 3

What is the difference between oceanic and continental crust?

Answer 3

Oceanic crust is thinner(5-10km) and more dense

Continental crust is thicker(30-50km) and less dense

Question 4

Why do plates move?

Answer 4

Plates move due to the movement of liquid magma deep within the earth. The movement of magma creates convection currents, which are flows of heat.

Question 5

What is the place that plates meet are called?

Answer 5

Plate margins or plate boundaries

Question 6

How do convection currents work?

Answer 6

• The core heats up the magma in the mantle
• The hot magma is less dense than its surroundings, so it rises upwards
• When it reaches the top it cools
• It becomes more dense, and therefore sinks back down to the bottom
• It is heated up again and the cycle continues
• The plates which lie on top, are pushed and pulled by the convection currents in the magma.

Question 7

How do tectonic plates move in relation to each other?

Answer 7

Very slowly and in different directions

Question 8

What is the global distribution of tectonic hazards?

Answer 8

Tectonic hazards(earthquakes and volcanoes) occur on plate boundaries. There is a clear pattern of earthquake and volcano distribution along plate boundaries, such as along the west of north america and south america or in the Atlantic ocean between Africa and south america called the Mid-Atlantic ridge.

Question 9

What is an example of an area with high volcanic and earthquake activity?

Answer 9

The ring of fire, which is located in the pacific ocean.

Question 10

Why do earthquakes occur along plate margins?

Answer 10

Due to plate movements causing vibrations

Question 11

Why do volcanoes occur on plate margins?

Answer 11

As magma(molten rock underground) feeds volcanoes and this magma can get to the surface at certain plate boundaries.

Question 12

Why do sometimes volcanic eruptions can happen in the middle of a plate margin?

Answer 12

Volcanoes do not always occur on plate boundaries because, this is where magma breaks through the middle of the plate(usually when the crust is thin)and travels up to the surface, which is known as a hotpots, e.g Hawaii in pacific ocean.

Question 13

Why do sometimes earthquakes don’t occur at plate margins?

Answer 13

This may be caused by human activity such as underground mining or oil extraction.

Question 14

What are earthquakes?

Answer 14

An earthquake is a sudden and violent period of ground shaking.

Question 15

What are volcanoes?

Answer 15

A volcano is a large and often conical shaped land form usually formed over a long period of time by a series of eruptions.

Question 16

What are the 3 main types of plate margins?

Answer 16

Constructive, destructive(includes collision),

conservative

Question 17

What are constructive plate margins?(short answer)

Answer 17

Where two plates are moving apart

Question 18

What are destructive plate margins?(short answer)

Answer 18

Where two plates are moving towards one another

Question 19

What are conservative plate margins?(short answer)

Answer 19

Where two plates are sliding alongside each other

Question 20

Explain what happens at a constructive margin?

Answer 20

At a constructive plate margin, the plates are moving away from each other.
When the two plates are pulled apart, magma rises in between the gap left by the two plates separating.(When magma is above ground, it is called lava), lava then pours out onto the surface.
Volcanoes form in the areas where lava pours out. This lava is usually runny and free flowing which creates flatter volcanoes. Earthquakes also occur here as the plates shake and vibrate when they move apart.
This process can happen on continental crust or oceanic crust.
When new land is formed on the ocean floor it is known as sea floor spreading.
When lava cools it forms rock. Over time this rock builds up and can form islands e.g Iceland is a volcanic island and sits on the mid Atlantic ridge.

Question 21

Explain what happens at the destructive margin?

Answer 21

At a destructive plate margin, the plates move towards each other.
This causes one of the plates to subduct below the other into the mantle, where it is destroyed.
The denser oceanic crust subducted below the continental crust.
The plate that is subducting leaves a deep ocean trench.
The friction between the two plates causes strong, deep earthquakes
The oceanic crust is melted as it is pulled deeper into the mantle, creating magma which is less fluid than at the constructive margin. The magma causes pressure to build up under the crust.
Eventually the magma pushes out through the crust to the surface, creating explosive volcanoes and steep sided composite volcanoes. Eruptions are often very violent and explosive.

Question 22

What is an example of destructive plate boundaries?

Answer 22

The oceanic Nazca plate which is relatively dense is subducted beneath the less dense South american continental plate.

Question 23

What happens when two continental plates?

Answer 23

There is no subduction, this is called collision, where two plates collide and the crust becomes crumpled upwards. The collision forms fold mountains such as the Himalayas. Earthquakes can occur at collision boundaries but there are no volcanoes because there is no magma.
Collision margins are a type of destructive margins

Question 24

What happens when two oceanic plates meet?

Answer 24

The denser plate sinks below and islands in the ocean can form e.g the Mariana trench.

Question 25

Explain what happens at a conservative plate margin?

Answer 25

At a conservative plate margin two plate are moving past each other at different speeds. When these plates move side by side, friction between the plates builds up. The friction builds up over many years and eventually the pressure becomes very big and the plates move in a sudden jolt. This releases a lot of energy and causes earthquakes.
On oceanic crust, this movement can displace a lot fo water, which causes large waves called tsunamis.
On continetal crust, fault lines can occur where the ground is cracked by the movement e.g San Andreas fault in CA.
There are no volcanoes on conservative plate margins because no magma is being generated.

Question 26

Compare Chile’s and Nepal’s contrasting levels of wealth?

Answer 26

Chile’s GDP is 38th out of 193 countries, however Nepal’s is 109th.
Chile’s human development index is 41st out of 187 countries, on the other hand Nepal’s is 145th in the world.

Question 27

When did Chile’s earthquake happen?

Answer 27

27th February 2010

Question 28

When did Nepal’s earthquake happen?

Answer 28

25th April 2015

Question 29

What happened in the Chile earthquake?

Answer 29

A huge earthquake measuring 8.8 on the Richter scale struck of the coast of Chile, lasting 3 minutes.
The earthquake occurred on a destructive plate margin, where the Nazca plate subducts beneath the south american plate. Smaller aftershocks followed the initial earthquake.
As the earthquake occurred in the Pacific ocean, the plate movement displaced a lot of seawater, triggering a tsunami.

Question 30

What happened in the Nepal earthquake?

Answer 30

On 25th April 2015, a 7.9 magnitude earthquake hit Nepal. Caused by the subduction of the indo- Australian plate beneath the Eurasian plate(destructive). The earthquake’s epicentre was around 80km away from Nepal’s capital, Kathmandu.
The earthquake originated only 15km below the surface which meant it was felt very strongly on the surface. Huge avalanches and land slides were triggered in the Himalayas which run through Nepal.
Damage from the earthquake extended 100s of km into neighboring countries, and severe aftershocks occurred afterwards.

Question 31

What are the primary effects in Chile?

Answer 31

• Around 500 killed and 12k injured, 800,000 people affected overall
• Many buildings were destroyed, including 22,000 homes, 4500 schools, 53 ports and 56 hospitals. The Santiago airport was badly damaged.
• Water, electricty and commnications lost in many places. Many well constructed buildings were left standing after the earthquake.
• Estimtated cost of 30 billion US dollars.

Question 32

What are the secondary effects in Chile?

Answer 32

• Landslides triggered by the earthquake damaged 1500km of roads. Debris blocked roads for weeks, which cut off rural communities and slowed relief efforts.
• A tsunami was triggered by the earthquake, which devastated coastal towns and destroyed ports. The tsunami also hit other Pacific countries.
• Fires broke out in buildings due to burst pipes and other complications. A fire in a chemical plant near Santiago meant many people had to be evacuated.

Question 33

What are the primary effects in Nepal?

Answer 33

• 9000 people killed and 20,000 injured. 8 million people affected(1/3 of Nepal’s population)
• 3 million people left homeless after homes were destroyed
• 7000 schools destroyed and 50% of all shops destroyed, leading to food and supply shortages.
• Power, water and communications were severely destroyed
• 1.4 million people were urgently in need of food, water and shelter
• Cost of damage was 5 billion US dollars
• Many historical sites and landmarks were destroyed

Question 34

How common are earthquakes in Chile and Nepal?

Answer 34

Earthquakes in Chile are quite common. Local communities and the government were prepared and knew how to respond quickly and effectively to the earthquake.
Earthquakes in Nepal are not uncommon. Scientists have identified a pattern of large earthquakes in this region around every 80 years. Despite this warnings and new building regulations, little has been done to prepare the city and it’s people for when an earthquake struck.

Question 35

What are the immediate responses in Chile?

Answer 35

Emergency services acted swiftly. International help needed to supply field hospitals, satellite phones and floating bridges.
Temporary repairs made to the important Route 5 north-south highway within 24 hours, enabling aid to be transported from Santiago to affected areas.
Power and water restored to 90% of homes within 10 days.
A national appeal raised US 60 million dollars- enough to build 30,000 small emergency shelters.

Question 36

What are the long term responses in Chile?

Answer 36

A month after the earthquake Chile’s government launched a housing reconstruction plan to help nearly 200,000 households affected by the earthquake.
Chile’s strong economy, based on copper exports, could be rebuilt without the need for much foreign aid.
The presidant announced it could take 4 years for Chile to fully recover from the damage to buildings and ports.

Question 37

What are the immediate responses in Nepal?

Answer 37

Search and rescue teams, water and medical support arrived quickly from countries such as Uk, India and China.
Helicopters rescued many people caught in avalanches on Mount Everest and delivered supplies to villages cut off by landslides.
Half a million tents needed to provide shelter for the homeless.
Financial aid pledged from many countries.
Field hospitals set up to support overcrowded main hospitals
300,000 people migrated from Kathmandu to seek shelter and support with family and friends.
Social media widely used in search and rescue operations and satellites mapped damaged areas.

Question 38

What are the long term responses in Nepal?

Answer 38

Roads repaired and landslides cleared. Lakes, formed by landslides damming river valleys, need to be emptied to avoid flooding.
Thousands of homeless people to be rehoused and damaged homes repaired. Over 7000 schools to be re-built or repaired.
Stricter controls on building codes
In June 2015 Nepal hosted an international conference to discuss reconstruction and seek technical and financial support from other countries.
Tourism, a major source of income, to be boosted- by July 2015 some heritage sites re-opened and tourists were starting to return
Repairs to Everest base camp and trekking routes-by August 2015 new routes had been established and the mountain re-opened for climbers.
In late 2015 a blockade at the Indian border badly affected supplies of fuels, medicines and construction materials.

Question 39

Why do people choose to live in hazardous areas?

Answer 39

-Earthquakes and volcanic eruptions don’t happen very often. They are not seen as a great threat in most people’s lives.
-Better building design can withstand earthquakes so people feel less at risk.
More effective monitoring of volcanoes and tsunami waves enable people to receive warnings and evacuate before events happen.
Fault lines associated with earthquakes can allow water supplies to reach the surface. This is particularity important in dry desert regions.
Volcanoes can bring benefits such as fertile soils, rocks for building, rich mineral deposits and hot water.
Some people may not be aware of the risks of living close to a plate margin.
Plate margins often coincide with very favourable areas for settlement, such as coastal areas where ports have developed.
People living in poverty have other things to think about on a daily basis-money, food, security and family.

Question 40

Where is Iceland?

Answer 40

Iceland lies on the Mid-Atlantic ridge, a constructive plate margin that stretches through the middle of the Atlantic ocean.

Question 41

What is the tectonic activity like in Iceland?

Answer 41

There are several active volcanoes- an eruption occurs on average every 5 years. Earthquakes are common. Over 320k people live in Iceland and close to a million people visit the country every year.

Question 42

Even though earthquakes and volcanic eruptions are common in earthquake, why do so many people live there and why is it a popular tourist place?

Answer 42

Whilst the tectonic activity does pose a threat, the people in Iceland consider it to be a low risk. This is mainly due to effective scientific monitoring and awareness of the potential dangers. And tectonic activity brings huge benefits to the country.

Question 43

What are the benefits that tectonic activity gives Iceland?

Answer 43

• Hot water from within the Earth’s crust provides heat and hot water for nearly 90% of all buildings in Iceland.
• Volcanic rocks are used in construction for roads and buildings.
• Iceland’s dramatic landscape with waterfalls, volcanoes and mountain glaciers has become a huge draw for tourists. Tourism provides jobs for many people.
• Thousands of tourists visited Iceland after the recent eruption of Eyjafallajokull in 2010.
• Geothermal energy is used to generate 25% of the country’s electricity
• The naturally occurring hot water-some of which reaches the surface through cracks created by earthquakes is used to heat greenhouses and swimming pools.

Question 44

What are the four main management strategies for reducing the risks from tectonic hazards?

Answer 44

• Monitoring
• Prediction
• Protection
• Planning

Question 45

What is monitoring?

Answer 45

Using scientific equipment to detect warning signs of events such as volcanic eruption.

Question 46

What is prediction?

Answer 46

Using historical evidence and monitoring, scientists can make predictions about when and where a tectonic hazard may happen.

Question 47

What is protection?

Answer 47

Designing buildings that will withstand tectonic hazards

Question 48

What is planning?

Answer 48

Identifying and avoiding places most at risk

Question 49

How can you monitor for volcanic eruptions?

Answer 49

As magma rises through a volcano it gives a number of warning signs that an eruption is likely to occur.
All the world’s active volcanoes are closely monitoring by scientists. If an eruption seems likely, warnings can be issued and action taken to evacuate surrounding areas. Modern hi-tech equipment is used, some of which is located on the volcano itself.
Remote sensing- satellites detect heat and changes to the volcano’s shape.
Seismicity- seismographs record earthquakes
Ground deformation-changes to the shape of the volcano are measured using laser beams
geophysical measurements-detect changes in gravity as magma rises to the surface.
Gas- instruments detect gases released as magma rises.
Hydrology-measurements of gases dissolved in water

Question 50

How can you monitor for earthquakes?

Answer 50

Earthquakes generally occur without warning. Whilst there is some evidence of changes in water pressure, ground deformation and minor tremors prior to an earthquake, scientists have yet to discover reliable ways to monitor and predict earthquakes.

Question 51

How can you use prediction for volcanoes?

Answer 51

The prediction of a volcanic eruption is based om scientific monitoring. In 2010 an increase in earthquake activity beneath the ice cap in Iceland enabled scientists to make an accurate prediction about the eruptions.

Question 52

How can you use prediction for earthquakes?

Answer 52

It is impossible to make accurate predictions about earthquakes due to lack of clear warning signs.
However scientists studying historical records of earthquakes at plate margins have identified locations that they believe are at greatest risk.

Question 53

How can you use protection for volcanoes?

Answer 53

The sheer power of a volcanic eruption means that there is often little that can be done to protect people and property. However it is possible to use earth embankments or explosives to divert lava flows away from property.

Question 54

How can you use protection for earthquakes?

Answer 54

Earthquake protection is the main way to reduce risk. It is possible to construct buildings and bridges to resist the ground shaking.
Regular earthquake drills help people keep alert and be prepared.
It is possible to construct tsunami walls at the coast to protect people and important buildings like nuclear power stations.

Question 55

What are the features of an earthquake resistant building?

Answer 55

• Rolling weights on roof to counteract shock waves.
• Walls reinforced with steel and concrete to reduce movement
• Automatic shutters come down over windows to prevent broken glass falling
• Open areas for easy evacuation
• Shock aborbers to absorb ground shaking.

Question 56

How can you use planning for volcanoes?

Answer 56

Hazard maps have been produced for many of the world’s most dangerous volcanoes,showing the likely areas to be affected. They can be used in planning to restrict certain land uses or to identify which areas need to be evacuated when an eruption is about to happen.

Question 57

How can you use planning for earthquakes?

Answer 57

Maps can be produced to show the effects of an earthquake or identify those areas most at risk from damage. High value land uses such as hospitals, reservoirs and office blocks can then be protected in these vulnerable areas.