This document defines and provides examples of extreme natural events. It categorizes these events as climatic, tectonic, or surface events. The document also discusses the impacts of natural disasters in terms of time and distance. Additionally, it summarizes plate tectonic theory and describes the structure of the Earth, including the inner core, outer core, mantle, crust, and plates. Plate tectonics cause earthquakes and volcanoes near plate boundaries as the plates converge and diverge.

1. EXTREME
NATURAL EVENTS
YEAR 9 HUMANITIES

2. EXAMPLES
An extreme natural event is a natural event, which, because of the size
(magnitude) of the event or length of time that the event occurs over
(duration), becomes extreme, such as:
• Avalanches
• Droughts
• Floods
• Tropical Cyclones (also known as typhoons and hurricanes)
• Volcanic eruptions
• Coastal erosion
• Earthquakes
• Landslides
• Tsunamis
• Tornadoes

4. GLOSSARY
Natural events occur around us all the time and are not usually a
problem - for example:
• rain fall
• wind blows
• hill-side slips
• tide movements
An extreme natural event is an unusual natural event that will make
national or international headlines if people are affected. Fortunately,
these do not happen too often.

6. GLOSSARY cont.
A natural hazard is an extreme natural event with the potential to
cause harm to people and their property. People may be able to
prepare for these and may be able to do things to minimise their
impact(s).
A natural disaster is an extreme natural event that affects people.

8. EXTREME NATURAL EVENTS
Extreme natural events can be categorised into sub-groups:
• Climatic (caused by the weather and atmosphere - occur above the
surface of the earth)
• Tectonic (caused by the earth’s movements and inside the earth)
• Surface events (those that occur on the surface of the earth)

10. NATURAL DISASTERS IMPACTS - TIME AND DISTANCE
1. The effects of a natural disaster can be local (0-20km), regional (up
to 100km), national or global (world-wide).
2. The effects of natural disasters can also be immediate (straight
away), short-term (days and weeks) or long-term (months and
years).
3. Each natural disaster has effects which can be seen, felt and
measured, but can be difficult to predict.
4. One extreme natural event/hazard (e.g. volcanic eruption) can
trigger different natural events/hazards (e.g. tsunami, ash fall).

12. PLATE TECTONICS
The idea that plates could move about, first came from the idea of
continental drift theory.
This idea came about by looking at the coastlines and fossils of
different countries.
The coastlines of South America and Africa seemed to fit snugly
together and fossils found in both continents were very similar.
This suggested that once these continents may have been connected
and somehow had drifted apart.

14. PLATE TECTONIC THEORY
This theory had been disregarded for sometime because it could not be
proved (due to a lack of technology).
Eventually discoveries were made that proved that the seafloor was
spreading apart, giving some validity to the continental drift theory.
Expanding on these ideas gave the mechanism for a new train of
thought, the Plate Tectonic Theory.

17. STRUCTURE OF THE EARTH – THE INNER CORE
The Earth is made up of four distinct layers:
• 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.
• With its huge heat energy, the inner core is like the engine room of
the Earth.

19. STRUCTURE OF THE EARTH – THE OUTER CORE
The outer core is the layer surrounding the inner core. It is a liquid
layer, also made up of iron and nickel. It is still extremely hot, with
temperatures similar to the inner core.

21. STRUCTURE OF THE EARTH – THE MANTLE
The mantle is the widest section of the Earth.
It has a thickness of approximately 2,900 km.
The mantle is made up of semi-molten rock called magma.
In the upper parts of the mantle the rock is hard, but lower down the
rock is soft and beginning to melt.

23. STRUCTURE OF THE EARTH – THE CRUST
The crust is the outer layer of the earth.
It is a thin layer between 0-60 km thick.
The crust is the solid rock layer upon which we live.

25. TYPES OF CRUST
There are two different types of crust:
• continental crust, which carries land, and
• oceanic crust, which carries water.
The oceanic plate is denser (heavier) than the continental plate, as
they move together, the oceanic plate is forced underneath the
continental plate.

27. PLATES
The Earth's crust is broken up into pieces called plates.
Heat rising and falling inside the mantle creates convection currents
generated by radioactive decay in the core.
The convection currents move the plates.
Where convection currents diverge near the Earth's crust, plates move
apart.
Where convection currents converge, plates move towards each other.
The movement of the plates, and the activity inside the Earth, is called
plate tectonics.

28. The world map above shows the main plate boundaries of the world.
The names often reflect which part of the world these are located in.

29. PLATE TECTONICS
Plate tectonics cause earthquakes and volcanoes.
The point where two plates meet is called a plate boundary.
Earthquakes and volcanoes are most likely to occur either on or near
plate boundaries.

31. PLATE TECTONICS
Plate tectonics cause earthquakes and volcanoes.
The point where two plates meet is called a plate boundary.
Earthquakes and volcanoes are most likely to occur either on or near
plate boundaries.