1. Year 9 Revision
Winter exam

2. RESTLESS EARTH

3. Structure of the Earth The Earth is made up of 3 main layers: Core
Mantle
The Earth is made up of 3 main layers:
Core
Mantle
Crust
Outer core
Inner core
The interior of the Earth is divided into layers based on chemical and physical properties.
The Earth has an outer silica-rich, solid crust, a highly viscous mantle, and a core comprising a liquid outer core that is much less viscous than the mantle, and a solid inner core.
Working from the centre of the Earth out we have:
The inner core is a primarily solid sphere about 1220 km in radius situated at Earth's center.
Based on the abundance of chemical elements in the solar system, their physical properties, and other chemical constraints regarding the remainder of Earth's volume, the inner core is believed to be composed primarily of a nickel-iron alloy, with small amounts of some unknown elements.
The temperature is estimated at 5,000-6,000 degrees Celsius and the pressure to be about 330 to 360 GPa (which is over 3,000,000 times that of the atmosphere!)
The liquid outer core is 2300 km thick and like the inner core composed of a nickel-iron alloy (but with less iron than the solid inner core).
Iseismic and other geophysical evidence indicates that the outer core is so hot that the metals are in a liquid state.
The mantle is approximately 2,900 km thick and comprises 70% of Earth's volume. (the core makes up about 30% of Earth's volume, with the outer crust [where we live] <1%!!).
The mantle is divided into sections based upon changes in its elastic properties with depth.
In the mantle, temperatures range between degrees Celsius at the upper boundary with the crust to over 4,000 degrees Celsius at the boundary with the core.
Due to the temperature difference between the Earth's surface and outer core, and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle (mantle convection cells). Hot material rises up as mantle plumes (like a lava lamp!), while cooler (and heavier) material sinks downward to be reheated and rise up again.
- We shall see that this process is very important for plate tectonic motion…
The outer most layer is the crust - this is the most familiar to us as it is where we live.
The distinction between crust and mantle is based on chemistry, rock types and seismic characteristics.
Presenter: Ask the students to guess what the most abundant element in the earth’s crust is…..they may be surprised to learn that it is actually Oxygen (46.6% Oxygen; 27.7% Silica; 8.1% Aluminum; 5.0% Iron; 3.6% Calcium; 2.8% Sodium; 2.6% Potassium; 2.1% Magnesium; plus trace elements)
Click to next slide for more on the Crust….
Crust

4. World Plates This diagram shows the major Tectonic Plates.
Presenter: Point out the UK, sitting on the Eurasian Plate. Also the plate boundary between Africa and South America (note that it has the same shape as the coastlines in these countries).

5. What are earthquakes and where do they occur?
Earthquakes are vibrations caused by movements at plate margins and at fault lines (cracks in the earth’s surface).
They can occur at all 4 major plate boundaries but the most severe earthquakes are normally found at CONSERVATIVE and DESTRUCTIVE plate margins.
DESTRUCTIVE
CONSERVATIVE

6. Why do earthquakes happen?

7. How can we measure earthquakes?
The Richter Scale 1 2 3 4 6 5 9 8 7 10
This measures the magnitude of a tremor (how powerful it is) using an instrument called a seismograph.
On the Richter Scale, magnitude is expressed in whole numbers and fractions.
It is a logarithmic scale which means that a size ‘6’ on the Richter Scale is 10 times larger than a size ’5’ and 100 times larger than a size ‘4’.
Richter Scale
The largest earthquake ever recorded was in Chile. It measured 8.9 on the Richter Scale.

8. Mercalli Scale
Mercalli Scale
This measures how much damage is caused by the earthquake based on observations. It is measured on a scale between I and XII.

9. Epicentre and focus

10. How can we limit earthquake damage?
predict
plan
protect
water levels can rise in wells and lakes because of cracks in the rock
a tiltmeter can check any movement within the rocks
1. predict
foreshocks before the main quake can be detected by a seismometer
animals can act strangely before the earthquake

11. How can we limit earthquake damage?
advise people to plan for an earthquake (eg tell them to turn off the gas, find a ‘safe’ place in their homes, pack an emergency kit)
make an emergency plan
2. plan
enforce regulations to make some buildings earthquake proof
organize regular ‘earthquake practices’ for offices and schools
What should people pack in their emergency kit?
Design a poster reminding people what to do in an earthquake.

12. Impacts
Primary
Secondary

13. TSUNAMI
What do you know?

14. What caused the tsunami?

15. VOLCANOES Volcanic bombs, ash, lava, gases Magma chamber
Parasitic cone
Crater
Main vent

16. At destructive plate boundaries the lava is viscous (thick like treacle) and it cannot flow very far from the volcano’s vent. This makes the volcano steep sided.
At constructive plate boundaries the lava is runny and it can flow far away from the volcano’s vent. This makes the volcano gentle sided.

17. Do all volcanoes erupt?
Active volcano – liable to erupt e.g. Mt Etna.
Dormant (sleeping) volcano – a volcano which has not erupted for many years. For example, Mt Pinatubo erupted in 1991 after 500 years of dormancy.
Extinct volcano – a volcano which has not erupted for many thousands or millions of years e.g. Edinburgh.
However, it is often very difficult to tell whether a volcano will erupt again…El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years!

18. Mt St Helens – the eruption
Animation showing the Mt St Helen’s eruption with text.

19. Why do people live in volcanic areas?
This lava is weathered (broken down) to form a fertile soil,
Can you think of any other reasons?
Geothermal energy (heat from the earth) can be produced in many volcanic areas.
Tourists are attracted to areas of volcanic activity.

20. EXTREME WEATHER

21. HURRICANES

22. How do hurricanes form?

23. Hurricane Katrina
Hurricane Katrina hit New Orleans on the morning of the 29th August 2005 bringing with it terrible destruction.
Winds of over 250 kilometres per hour were recorded as Katrina hit the coast, causing a storm surge 8.5 metres high.
Photo Credit: (top left) NASA/Jeff Schmaltz, MODIS Land Rapid Response Team
Photo Credit: (bottom right) Blank Map of the USA created by Brianski, Altered and reproduced under the term of the GNU Free documentation License. For Full details on conditions of use please refer to Please note that this license refers only to the USA blank map and not to any other images, text or animation which remain under copyright unless duly noted.
New Orleans

24. Effects of Hurricane Katrina
80% of the city was flooded and over a million homes were left without electricity. Over 1,800 deaths were caused by the storm, around 700 of them in New Orleans.
In some areas the flood level rose to over six metres. Those that had decided to stay in their homes had to either find high ground and await rescue or risk swimming and wading through polluted floodwater.
Photo Credits: Images courtesy of Federal Emergency Management Agency

25. TORNADOES – do you know the answers to these questions?
Why do they happen?
What states do you find in Tornado Alley?
What is Tornado Watch?
What is Tornado Warning?
What is the Fujita scale?

26. Why do people live in areas that suffer from extreme weather?

27. How to cross this huge country and keep your carbon footprint small?