1. Natural Disasters

2. Symbols
I do: my turn to talk. This is the explanation section of our lesson where you are required to listen. We do: this is where we discuss or work on the concepts together. You do: your turn to be involved. You may be working in a group or on an activity individually.

3. Tuning In: Layers of the Earth
Do you ever think about what lies beneath the ground you walk on every day? Yes, it is the Earth beneath our feet… but what is the Earth made from? How old is it? How deep is it? How hot is it? Take the quiz on the following slides to find out!

4. Question 1 How old is planet Earth? a) 4.5 thousand years
b) 4.5 million years
c) 4.5 billion years
The correct answer is… c)
The Earth is approximately 4.5 billion years old.

5. Question 2 How many layers are inside the Earth? a) 40 b) 14 c) 4
The correct answer is… c)
The Earth has four layers.

6. Question 3 The outer layer of the Earth is the layer we walk on.
What is this layer made from?
a) oxygen
b) rocks
c) sand
The correct answer is… b)
The outer layer of the Earth is made from rocks.

7. Question 4
The outer layer of the Earth has pieces, much like a jigsaw puzzle.
How many pieces are there?
a) 7
b) 17
c) 27
The correct answer is… b)
The outer layer of the Earth has 17 pieces.

8. Question 5
The layer beneath the surface of the Earth is called the mantle.
What is this layer made from?
a) magma (melted rock)
b) liquid metal
c) water
The correct answer is… a)
The mantle is made from magma (melted rock).

9. Question 6
Beneath the mantle are two layers called the outer core and the inner core.
What are these layers made from?
a) boiling water
b) hot gasses
c) iron and nickel
The correct answer is… c)
The outer and inner cores are made from iron and nickel.

10. Question 7
How many kilometres is it from the crust of the Earth to the inner core?
a) about 600 kilometres
b) about 6000 kilometres
c) about kilometres
The correct answer is… b)
It is about 6000 kilometres from the crust to the inner core.

11. Question 8 How hot is the inner core of the Earth?
a) about 50 degrees Celsius
b) about 500 degrees Celsius
c) about 5000 degrees Celsius
The correct answer is… c)
The inner core of the Earth is about 5000 degrees Celsius.

12. The Layers of the Earth
The Earth has four main layers: the crust, the mantle, the outer core and the inner core.
The crust is the layer upon which we live. It is made up of rock. The crust is about 70 km thick on land (the continental crust) and about 5 km thick under the ocean floor (the oceanic crust).
The mantle is the layer underneath the crust. It is made up of both solid and liquid rock. The mantle is much thicker than the crust. It is around km deep.
The outer core is the layer underneath the mantle. The outer core is made up of liquid (melted) iron and nickel. It is around 2000 km thick.
The inner core is at the very centre of the planet. It is also made up of iron and nickel. However; due to the intense pressure surrounding it, the metals exist in a solid state. The inner core is around 1200 km thick.

13. Activity: The Boiled Egg
The layers of a hard-boiled egg are similar to the layers of our Earth.
In fact, the crust of the Earth is approximately the same proportionate thickness as the shell is to the egg.
Carefully cut through a hard-boiled egg. Draw and label what you see in the cross-section.
Answer the questions on the Layers of the Earth worksheet.

14. Plate Tectonics
Although it seems like the crust is stable ground beneath our feet; in actual fact, it is constantly moving. The reason we cannot feel this movement is that it is extremely slow; only a few centimetres each year.
The part that is moving is made up of the Earth’s crust and the upper mantle. Together, this layer is called the lithosphere. The lithosphere floats on a layer of melted rock called the asthenosphere.
The lithosphere is made up of seven major plates and numerous minor plates. The seven major plates are the African, Antarctic, Eurasian, North American, South American, India-Australian and the Pacific plates.
Tectonic plates can slide past each other (transform boundaries), slide away from each other (divergent boundaries) or slide towards each other (convergent boundaries). These movements can contribute to events such as earthquakes, volcanic eruptions and tsunamis.

17. Review Complete the Plate Tectonics cloze activity.
Discuss the answers as a class.

18. Tuning In: Natural Disasters
What causes natural disasters?
Some natural disasters are geological. This means that they are caused by natural events occurring within the Earth’s crust.
Some natural disasters are meteorological. This means that they are caused by extreme weather conditions in the Earth’s atmosphere.
Some natural disasters are hydrological. This means that they are caused by the amount of water present on the Earth’s surface.
Some natural disasters can be caused by a combination of natural factors. Humans can also play a role in causing natural disaster events.
Can you brainstorm some natural disasters that would belong to each of these categories?

19. Geological Natural Disasters
Geological natural disasters are caused by natural events occurring within the Earth’s crust.
Some geological natural disasters include:
Earthquakes
Volcanoes
Tsunamis
Avalanches
Let’s investigate the causes and effects of these four geological natural disasters.

20. Earthquakes
Earthquakes occur when the tectonic plates that make up the Earth’s surface move apart, bump into each other, or slide under each other.
When two tectonic plates suddenly move or collide, seismic waves (vibrations which carry energy) move outwards. This point is called the focus.
Since the focus is usually deep underground, the location of the earthquake is often referred to as the point on the Earth’s surface directly above the focus. This point is called the epicentre.
Geologists use an instrument called a seismograph to measure the strength of the seismic waves created by an earthquake. This then enables the size of the earthquake to be measured using the Richter scale.
Scientists have not yet discovered a way of predicting exactly when and where an earthquake will occur. However, they do know that earthquakes occur along fault lines, and we know where these fault lines are.

21. What features of an earthquake can you see on the diagram?

22. Volcanoes
A volcano is a mountain with a crater or vent which allows hot lava, rock fragments, volcanic ash and gases to erupt from the Earth’s crust.
Volcanoes are usually located along fault lines where tectonic plates meet.
Lava is semi-fluid rock which has been heated under the surface of the Earth. Initial flows of lava can move at up to 10 km/h. Once a lava flow becomes established, it can move as fast as 60 km/h.
Along with lava and ash, volcanoes release gases. Common volcanic gases include water vapour, carbon dioxide, sulphur dioxide, hydrogen chloride and hydrogen sulphide.
Volcanic eruptions can vary in their size and level of explosiveness. Scientists use the Volcanic Explosivity Index, based on a range of characteristics, to measure the size of a volcanic eruption.

23. What features of a volcanic eruption can you see on the diagram?

24. Tsunamis
Tsunamis are caused by underwater earthquakes. Shockwaves cause the water level to rise above sea level, then gravity pulls the water into a giant and powerful wave.
Tsunamis can travel at speeds of 805 km/h (as fast as a jet plane).
Tsunamis are generally unnoticed out in the ocean, forming only a slight swell. As the tsunami approaches the shore and hits shallow water, it slows down but increases in height.
A typical wave period for a destructive tsunami is about 12 minutes. During this time, the wave will both peak and recede, causing wide-spread destruction on land and sweeping debris back out to sea.
The Pacific Tsunami Warning System, based in Hawaii, monitors seismic activity in the Pacific Ocean. When large underwater earthquakes are detected, tsunami warnings can be issued to affected populations.

25. What features of a tsunami can you see on the diagram?

26. Avalanches
Avalanches are a rapid flow of snow down a sloping surface. They are caused by four factors: a steep slope, snow cover, a weak layer in the snow cover and a trigger.
Natural avalanche triggers may include increased snowfall, melting snow, wind, rain, earthquakes, rockfall and icefall. Artificial avalanche triggers may include skiers, snowmobiles and controlled explosions.
Avalanches have the ability to transport enormous masses of snow at high speeds. As well as snow, avalanches may also carry stones, boulders and trees with them.
Avalanches are most common during the seasons of winter and spring. In mountainous areas, avalanches pose a very serious threat to life and property.
There are three main categories of avalanche: a dry snow avalanche, a wet snow avalanche and a slab avalanche. These avalanches vary according to their size, composition and destructive properties.

27. What features of an avalanche can you see on the diagram?

28. Meteorological Natural Disasters
Meteorological natural disasters are caused by extreme weather conditions in the Earth’s atmosphere.
Tropical cyclones (also known as hurricanes, typhoons or tropical depressions) are one example of a meteorological natural disaster.
Let’s investigate the causes and effects of this example.

29. Tropical Cyclones
Cyclones are intense tropical storms with powerful winds and heavy rain. They can also be referred to as hurricanes, typhoons or tropical depressions.
Cyclones usually begin over warm seas where there is low atmospheric pressure. The warm, moist air begins to spiral into a strong, circling storm.
Once crossing over onto land, cyclones typically weaken. This is because they are cut off from their primary energy source.
Cyclones have three main parts: the rainbands, the eye and the eyewall. Weather in the eye of a cyclone is usually calm. The diameter of the eye is usually around 50 km in length, but can be as large as 320 km.
Cyclone intensity is measured by the storm’s wind speed, on a scale of The strongest cyclones are known as category 5 and can move as quickly as 300 km/h. Winds this fast cause intense damage, such as ripping trees from the ground and flattening buildings.

30. What features of a tropical cyclone can you see on the diagram?

31. Hydrological Natural Disasters
Hydrological natural disasters are caused by the amount of water present on the Earth’s surface.
Some hydrological natural disasters include:
Flooding
Drought
Let’s investigate the causes and effects of these two hydrological natural disasters.

32. Flooding
Flooding occurs when a piece of land (that is usually dry land) is submerged under water. Some floods happen suddenly and recede quickly, while others take days or months to build and regress.
Flooding can be caused by thawing snow and ice, heavy rain or storm surges. This can lead to overflowing drainage systems, rivers breaking their banks, dam failure and elevated sea levels.
Flash floods are fast-moving flood waters effecting low-lying areas, such as canyons and valleys. These can happen after heavy rain from a slow moving thunderstorm. Flash floods are particularly dangerous, as they strike quickly with little warning.
Like other natural disasters, floods can be categorised according to their level of severity. However; even minor floods are dangerous. Flood waters should be avoided at all times.

33. What features of flooding can you see on the diagram?

34. Drought
Droughts occur when there is a period of below-average rainfall in a particular area. This can cause top soil to dry out, groundwater to sink and streams and rivers to dry up.
A drought can last for weeks, months or even years. In severe cases, droughts may be declared after as few as 15 days.
Living organisms need water to survive. Because of this, droughts are one of the worst natural disasters that can occur. Prolonged drought can cause plants and animals to die and crops to fail. This can lead to famine for the human population.
In areas where there aren’t many trees, droughts can cause erosion. Hot winds blow away the dry topsoil, which creates terrible dust storms.
There are three main categories of drought: meteorological (a reduction in rain), agricultural (a reduction in crop irrigation) and hydrological (a reduction in lake and reservoir levels).

35. What features of a drought can you see on the diagram?

36. Other Natural Disasters
Some natural disasters are difficult to classify into one category. This is because they are often caused by a combination of natural events (such as climate or extreme weather) and human actions (such as irresponsibility or careless land use).
Bushfires are one example of a natural disasters which has both natural and human causes.
Let’s investigate the causes and effects of this example.

37. Bushfires
Bushfires are uncontrollable blazes that usually start in areas of bushland or wilderness. They can be caused by lightning, agricultural clearing, campfires and dropped cigarettes. Some bushfires are deliberately lit.
Bushfires are very destructive and extremely dangerous. They are large, fast- moving and difficult to bring under control. Bushfires can even jump over gaps that are in their path, such as rivers and roads.
Bushfires are more frequent during the hottest and driest months of the year. Whilst every continent (except Antarctica) experiences bushfires, they occur most commonly in Australia.
Even though bushfires cause extensive damage, they play an important role in nature. Bushfires burn plants and trees which may be old and diseased, making way for new plants and trees to grow in their place.
There are two main categories of bushfire: mountainous (fires on hilly areas) and grassland (fires on flat areas).

38. What features of a bushfire can you see on the diagram?

39. Review Complete the Natural Disasters Match Up worksheet.
Discuss the answers as a class.

40. Tuning In: Effects of Natural Disasters
So far, we have learned about a wide range of natural disasters. These natural disasters can have a variety of effects on the environment and on human populations.
Work with a partner. Brainstorm as many potential effects of natural disasters as you can. Record these as a mind map.
What ideas did you come up with?

41. Effects of Natural Disasters
Displaced populations – due to the widespread destruction of buildings and property, many natural disasters leave people without a home. This can cause a massive movement of survivors from one area to another; placing a huge amount of pressure on services such as health care and education.
Health risks – survivors of natural disasters are often in danger of becoming seriously ill, even after the immediate risk of the disaster event has passed. Health complications resulting from infection and disease can lead to rising death tolls if medical assistance is not readily available to survivors.
Food shortages – due to the destruction of crops and agricultural supplies, food can become scarce following a natural disaster. Aid organisations play a vital role in ensuring that survivors are provided with the nutritional support they need, including fresh, clean drinking water.
Emotional trauma – survivors of natural disasters are often at risk of conditions such as PTSD (post-traumatic stress disorder). Children in particular require special treatment to recover from these experiences.

42. Management of Natural Disasters
Natural disasters cannot be prevented. However; the risk to lives and property can often be lessened through the implementation of a sensible natural disaster management plan.
The management of a natural disaster event falls into four main categories:
1) Reducing the risks through appropriate town planning and building design
2) Being prepared by having an evacuation plan
3) Providing immediate relief to disaster-affected communities
4) Supporting the long-term recovery of disaster-affected communities.

43. Review
Complete the Effects and Management of Natural Disasters worksheet.
Discuss your ideas as a class.