Topic 1: Restless Earth
Part 1:
• Structure of the Earth
• Composition of the layers of the Earth
• Convection currents
• Global distribution of plate boundaries
• Types of plate boundary
• Types of volcano
Structure of the Earth:
The Earth has 4 main different layers:
1. Crust
2. Mantle
3. Inner Core
4. Outer Core
The crust and upper part of the mantle are also called the Lithosphere. The molten area of magma directly below this is often called the Asthenosphere.
Composition of the Earth’s Layers:
The Crust is made of either Oceanic Crust (sea) or Continental Crust (land).
 Continental crust – this forms the land. It is made mostly of granite (a low density, igneous rock). The continental crust is on average 30-50 km thick.
 Oceanic crust – this is made of basalt (it is denser than granite but is also an igneous rock).
Usually only 6-8 km thick.
Task: 1) State two differences between oceanic and continental crust (2 marks).
The Mantle is also solid like the crust and this combined solid layer is the Lithosphere. Just below this is the molten rock magma layer of the mantle. This flowing upper layer of the mantle affects the lithosphere and causes volcanoes and earthquakes.

Convection Currents:
Convection currents in the mantle are caused by heat generated by the core. This heat is due to radioactive decay of unstable elements in the core. As heat rises from the core it causes the molten
rock in the mantle to move, which in turn leads to the movement of the section of the Earth’s crust
called Tectonic Plates above it.
The liquid outer layer of the core is made of iron and as it moves it creates a magnetic field much like an electrical dynamo.
Task: Explain how tectonic plates move (4 marks).

Global Distribution of Plate Boundaries:
Map to show Major Tectonic Plate boundaries:
The Earth’s crust is split into separate pieces called tectonic plates. Where one plate meets another is called a Plate Boundary.
Task: Describe the distribution of plate boundaries. (2 marks)
Task: Identify the type of boundary found between: a) the Nazca plate and the South American plate. (Destructive) b) The Indo-Australian plate and the Eurasian plate (Collision) c) The Eurasian plate and the North American plate. (Constructive)
Types of Plate Boundary:
There are four different types of plate boundaries, depending on which direction the plates are moving:
Plate Boundary Example Earthquakes Volcanoes
Conservative
Direction/
Description
Plates slide past each other.
San Andreas Fault,
California USA.
North American and Pacific plates.
Destructive
Up to 8.5 magnitude.
Daily,small tremors.
No volcanoes.
Constructive Plates are pulling apart.
Iceland on the Mid-
Atlantic Ridge.
The Eurasian and
North American Oceanic plates
Small earthquakes up to 6.0 on the
Richter Scale.
Not very explosive or dangerous
Erupt in fissures
(cracks in the crust). Runny

Destructive
Japan
Earthquake
2011
Collision
Kashmir 2005
The Oceanic plate subducts under the continental plate
Andes Mountains in Peru
and Chile.
Nazca Oceanic
Plate is subducted under the
South American
Continental Plate.
Himalayas formed as the
Indian and Eurasian
Continental Plates push into each other.
Very destructive
Up to 9.5 magnitude.
Tsunamis can form.
Destructive earthquakes up to magnitude
9.0. Landslides are triggered. basalt lava eruptions
Very explosive destructive volcanoes.
Steep sided cone shaped.
Erupt with andesitic sticky lava.
No volcanoes
Earthquakes and volcanoes (tectonic hazards) occur at plate boundaries. Different plate boundaries produce different hazards. The direction of plate movement and the type of plate (oceanic or continental) dictate what type of hazard will occur.
Diagram to show: Types of Boundary:
Task: Explain why continental crust is thickest at collision boundaries. (2 marks)

Task: Explain why earthquakes happen on destructive plate margins. You may draw a diagram to help with your answer. (4 marks)
Types of Volcanoes:
At hot spots, (cracks in the surface of the crust) constructive and destructive plate boundaries
different types of volcano will form. These are constructed from different types of lava and erupt
in different ways.
 Made from Andesitic lava, which is very sticky.
 Causes violent eruptions.
 Made from layers of ash and lava.
 Gently sloping volcanoes
 Made from runny, Basaltic lava
 Erupts in gentle lava flows.
Task: Identify the main features of composite volcanoes (2).
Task: Identify the main characteristics of shield volcanoes. (2)
Task: Explain how the type of magma affects the shape that you have described.

Part 2:
• Effects of Earthquakes
• Effects of Volcanoes
• Managing Earthquakes
•Managing Volcanoes
Effects of Earthquakes and Volcanoes:
The effects of an earthquake depend upon:
 Magnitude (Richter scale)
 Depth
 Size
 Duration
The effects of a Volcanic eruption depend upon:
 Size
 Duration
Task: Explain how each of the above features make the hazard worse... e.g. the higher the magnitude of an Eq there more likely the damage.
Features of a volcanic eruption:
Volcanoes and earthquakes can cause more damage depending on:
 The level of development of the country (LEDC/MEDC) will greatly effect how prepared or able to respond the people are.
 The closeness of towns and cities to the epicentre (point on the Earth’s surface above the earthquake focus) of the earthquake or closeness to the volcano will also have an impact on how much damage is caused.
Effects are often classified as either Economic Effects, Social Effects or Environmental.
Effects can also be classified as either Primary Effects or Secondary Effects.
In LEDCs social effects are often much worse as people are not well prepared and emergency
services and buildings often can’t cope. This leads to a great loss of life and many casualties.

In MEDCs social effects are often much less, however economic effects are often much worse as people’s houses and possessions are far more valuable, so cost more to replace.
Primary effects are caused instantly by the earthquake or volcano such as roads cracking or
landslides happening.
Secondary effects are the long lasting effects following the hazard. This could be fires breaking
out, disease spreading or a shortage of food and water.
Earthquakes Case Studies:
Earthquakes cannot be predicted, and can be catastrophic. They are a sudden release of energy.
Underground, tectonic plates push against each other building up pressure. This is released suddenly along faults (cracks in the crust), sending out a huge pulse of energy as earthquake waves.
Magnitude:
The amount that an earthquake shakes the ground is called its magnitude. A seismometer measures this using the Richter scale.
Diagram to show Focus and Epicentre
Developing Country (LEDC) Earthquake: Kashmir Sat 8 th October 2005 or Haiti 2010
Location and other info
Cause
Plate boundary/ cause
Kashmir
October
2005
Magnitude
7.6 on the
Richter
Scale
Eurasian and
Indo –
Australian plates to form a Collision Plate boundary.
Social
Death toll
– 75,000
Injured –
75,000
Homeless
– 2.8 million
Disease
Impacts
Economic
Cost -
$440million
Property
Environmental
Landslides
Responses
Shelter Box
Charity provide tents for people to get shelter
People move from the devastated mountain villages to camps in the lowlands

Task: Add more information to Impacts and Responses
Task: Categorise impacts and responses into Primary and Secondary.
Developed Country (MEDC) Earthquake: San Francisco 1989 or Kobe Japan 2005 or
Christchurch, New Zealand 2011
Cause Impacts
Location Plate Boundary Social Economic Environmental Responses
Loma Prieta
(California)
Earthquake
17 th October
1989
Magnitude
6.9 on the
Richter Scale
San Andreas
Fault,
California USA.
North
American and
Pacific plates slide past each other.
Conservative plate boundary
Death toll –
63
Injured –
3,757
Homeless –
12,000
Property
Cost - $10 billion
The
Cypress
Street
Viaduct collapsed
22 Fires causing pollution
1,000 landslides and rockfalls
Task: Add more information to Impacts and Responses.
Task: Categorise impacts and responses into Primary and Secondary.
Emergency services helped to save people and fight fires.
Built better buildings that would survive extreme eqs.
Volcano Case Studies:
When volcanoes erupt they create many different effects depending on both the type of eruption and the level of development of the country
Developing Country (LEDC) Volcano: Chances Peak, Montserrat 1997
Social
Impacts
Economic Environmental Responses Location
Cause
Plate
Boundary
.
A Small island in the
Caribbean 12 miles wide
Destructive boundary:
Caribbean and North
American
Plates
23 people died
Secondary
Airport and port closed
Farmland destroyed
Schools and hospitals destroyed.
Secondaryef fects:
2/3 of the island covered in ash
Forest fires caused by pyroclastic flows
Tiny island, so no-where for islanders to evacuate to.
2/3 of the population have now emigrated away
50% of population

effects:
As most of the southern area was destroyed any remaining inhabitants have had to endure harsh living conditions in the North.
Transport remains a problem for people travelling to the island as the port and airport remains closed.
The tourist industry is still suffering.
Task: Add more information to Impacts and Responses.
Task: Categorise impacts and responses into Primary and Secondary.
Developed Country (MEDC) Volcano: Mount St Helen’s 1980
Cause Impacts
Location Plate Boundary
Mount St.
Helens,
Washington
State,
USA
1980
Destructive plate boundary
Juan de Fuca plate meets the
North American plate
Social
57 people died in the eruption - most from poisonous gases
Economic
Flooding resulting from blocked rivers washed away road and rail bridges
Crops were ruined
Livelihoods of loggers were devastated
Environmental
Lava flows and ash filling in Spirit
Lake
Logs and ash blocked the
Toutle River causing big floods.
Large number of wildlife were killed by the blast and the volcanic ash with nothing surviving in the blast zone
Large areas of trees being flattened like matchsticks
Task: Add more information to Impacts and Responses.
Task: Categorise impacts and responses into Primary and Secondary. evacuated to the north of the island to makeshift shelters
Secondary
Response
Over half the population left the island and have not returned.
Responses
An evacuation zone of 5 miles was made before the eruption.
Robots are now sent to get sample of sulphur, not people!

Although Mount St Helens was the far more explosive volcano and killed more people, the effects
of the Montserrat eruption were much worse. This is due to the people of Montserrat not being
able to respond to the eruption as effectively as those who lived near Mount St Helens.
Task: Using examples, Explain why some areas are more vulnerable to hazards than others. (4)
Task: Using examples, Describe the social impacts of a volcanic eruption. (2)
Task: Explain why some volcanic eruptions cause much more loss of life than others. (2)
Managing Earthquakes and Volcanoes:
We manage natural hazards by trying to reduce/mitigate the damage to both people (social) and property (economic). We can do this in a number of ways; these can usually be classified as either
Preparation or Response.
Preparation
Measures that are taken in advance of the earthquake or volcano happening include:
 Monitoring or prediction (very important for volcanoes),
 Practicing evacuation drills
 Making evacuation plans and Hazard maps.
 Improving building design
 Stock piling emergency supplies such as tents, water and medicines.
Response
These are measures that take place immediately after the earthquake or volcano. They are often classified as either Short term or Long term aid.
Short term aid includes:
 Providing emergency supplies such as water, food and tents.
Long term aid includes:
 Rebuilding houses and roads
 Providing loans to help the area improve.
Prediction:
By being able to predict when a volcano will erupt we can prepare and respond to a hazard much better. People can evacuate the people and do our best to save their lives:
 An aircraft is used to measure the amount of gas given off by the volcano.
 Tunnels in the volcano have seismometres which monitor earthquakes which increase as magma rises.
 Tiltmetres detect when the volcano swells up as it fills with magma.
 Boreholes measure the temperature of the water as the magma heats it up.
 Concrete lahar (volcanic mudslide) channels divert dangerous mudslide.
 Hot springs are monitored.

 Shelters are made from concrete to protect against volcanic bombs and ash.
 People have regular evacuation drills along routes which are clearly signposted.
Task: Using examples, explain how volcanic eruptions can be predicted (4 marks).
Mitigation – reducing the impact
Mitigation measures are taken to reduce the effect of the hazard and the scale of the disaster.
Measures include relocating people away from the hazard-prone areas and strengthening the design
of buildings and structures – using hazard-resistant designs. This can mean bolting buildings to their
foundations and providing support walls, called ‘shear walls’. They are made from concrete that has steel rods in it to help strengthen the structure and help it stand up to rocking forces. Walls may also be reinforced and supported by diagonal steel beams in a technique called cross-bracing.
Task: In relation to the management of tectonic hazards, define and illustrate the terms ‘preparation and ‘mitigation’.
Task: Describe two ways in which building in developing countries can be made more resistant to earthquakes. (2 marks)
Task: Look back on the effects of the two volcanoes and earthquakes you have studied.
a) Compare impacts each had on people and property.
b) Explain the differences.