Restless Earth
AQA A Geography Revision Guide
The Structure of the Earth
•
•
•
•
•
•
Key Words:
Crust
Plates
Plate Margins
Mantle
Convection currents
Major Plates forming the earth’s crust
Continental and Oceanic Plates
OCEANIC
CONTINENTAL
Newer
Older
More dense so sinks below continental
plates.
Less Dense so remains above an oceanic
plate moving towards it
200 million years old
1500 million years old
Can be destroyed as it moves down and
melts in the mantle
Cannot be destroyed
Plate Margins – what happens? Why
does it happen? How does it happen?
Destructive Plate Margin – Crust is destroyed!
Constructive Plate Margin – Crust is made!
Conservative Plate Margin – Crust is not
destroyed or made – sliding!
Plate Margins
•
•
•
•
•
•
•
•
Key Words:
Collision
Subduction
Friction
Melting
Magma
Lava
Fault line
Make sure that you can draw and label and
explain the diagram below:
Fold Mountains – when plates move
together...
• CASE STUDY:
THE ANDES MOUNTAINS
Steep relief, poor soils!
Definition: “Large
mountain ranges where
rock layers have been
crumpled as they have
been forced together”.
Andes Mountains – Facts you need to
know...
• Longest mountain range in world: 7000km in
South America
• Average height 4000m!
• Caused by NAZCA and SOUTH AMERICAN PLATE
colliding.
How are they used?
Farming, tourism, mining,
energy from hydroelectric
power.
How can we make use of fold
mountains?
• Farming – In Bolivia, many SUBSISTENCE
farmers grow crops on steep slopes e.g.
potatoes. They create flat land by digging in
TERRACES into the side of the mountains.
Terraces: Collect rainwater, stop soil erosion of thin soils. Rainfall runs
off steep mountainside very quickly!
Some cash crops are grown such as soybeans, rice and cotton.
Idea: Make best use of the land! If the terraces were not there, soil
would be washed down the mountain and so farmers would not be
able to grow crops.
Andes Mountains – Facts you need to
know...
Mining
• Excellent area for mining tin especially Peru.
• Famous mine: Yanacocha gold mine. This is jointly
owned by a US company and a company based in Peru.
• POSITIVE: Mine brings jobs to Cajamarca (population
has gone from 30,000 when the mine began to 240,000
in 2005).
• NEGATIVE: Pressure on services e.g. shops, hospitals
and causes higher crime rates.
• NEGATIVE: Water sources contaminated by mining –
water quality has gone down.
Andes Mountains – Facts you need to
know...
• Hydroelectric power – rivers dammed, water
passed through turbines to create electricity.
• Steep and narrow valleys can be easily dammed.
• Melting snow in spring provides excellent water
supply BUT there is high variation of water supply
through then year – LOW in summer.
• Famous Hydroelectric projects: Yuncan and El
Platinal.
Andes Mountains – Facts you need to
know...
• Tourism! The Inca Trail and Machu Pichu.
• Machu Pichu is a very famous UNESCO world
heritage site.
• Inca Trail South America’s best known trek!
45km trek at 4200m altitude! You can see Inca
ruins, lush forest, mountain scenery.
• Other attractions: mountain peaks, volcanoes,
glaciers, lakes.
Ocean Trenches – when plates move
together...
Definition: “Deep sections
of the ocean, usually
where an oceanic plate is
sinking below a
continental plate”.
Some of the deepest
parts of the ocean!
Composite and Shield Volcanoes
• COMPOSITE volcanoes occur at DESTRUCTIVE
MARGINS.
• SHIELD volcanoes occur at CONSTRUCTIVE
MARGINS.
Both types have craters, magma chambers.
Can you
label the
crater, vent,
magma
chamber?
COMPOSITE
SHIELD
Steep slopes, narrow base
Gentle slopes, wide base
Has secondary vent and cone
Low rounded peak
Layers of thick lava and ash
Layers of runny lava with little
ash
Eruptions NOT frequent but
often VIOLENT
Eruptions frequent and nonviolent
Volcanoes
• An example of a natural hazard: an occurrence
over which people have little control, which
poses a threat to people’s lives and possessions.
A natural event is different as a volcano could
erupt in unpopulated areas without being a
hazard!
• The are found close to plate margins. The area
around the Pacific Ocean known as the PACIFIC
RING OF FIRE is especially prone to volcanic
eruptions.
Shield Volcano Case Study
• Name: Nyiragongo volcano, Congo
• Cause: Movement of plates in East African Rift valley
• Primary Effects – 60kph lava flow, lava flowed over runway closing
Goma airport, lava split town of Goma in 2. Many homes destroyed,
water pipes burst, fuel stores exploded, 45 people killed.
• Secondary Effects – 500,000 people fled to Rwanda to escape the
lava spending night on streets. No shelter, no clean water, no
electricity. Disease such as cholera was a real risk due to the shear
number of people.
• One week of aid arrived. Residents returned to Goma only to find
many houses had been looted (burgled) whilst they were away!
• Responses: Water supplied by tankers, Aid agencies helped e.g.
Christian Aid and Oxfam. Food, shelter, water distributed.
Composite Volcano Case Study
• Name: Mount St. Helens, USA
Dormant for many years. Steam filled with ash
exploded into air and residents told to leave in
March 1980.
8 km exclusion zone was introduced around the
crater.
‘This is like standing next to dynamite, and the
fuse it lit but you just cannot see how long the
fuse is...’!
Mount St Helens
• 8.32am 18th May, 1980.
• Earthquake of 5.1 on the Richter Scale triggered a
landslide on the NE side of the volcano!
• The earthquake triggered the volcano to erupt.
The rock, ash, glacier ice blasted out sideways
killing all living things 27km north of the crater!
• 57 people died. Spirit Lake fish and wildlife was
destroyed!
Responses to Mount St Helens, 1980
• Immediate Responses: Helicopters used for search and rescue. Emergency
treatment in nearby towns. Tourists rescued from mudflows. Attempts to
unblock roads covered in metre deep ash (completed 3 days after the
eruption). Millions of breathing masks sent to the area.
• Long-term Responses: Farm land used as ash had made it more fertile.
Buildings and bridges rebuilt. Forests re-planted. Roads rebuilt. Insects,
birds, wildlife slowly returned to area 10 years later.
• Now: very famous for tourists. Area designated as a national monument
gaining $1.4 million investment. 3 million visitors allowed to access Mount
St Helens each year. Johnston Ridge Observatory opened for tourists to
view Mount St Helens. The trees felled by the eruption still cover a quarter
of Spirit Lake but many are beginning to sink now!
Primary and Secondary Effects
• Primary effects: the immediate effects of the
eruption, caused directly by it.
• Secondary effects: the after-effects that occur as
an indirect effect of the eruption on a longer
scale.
Aid – money, food, training and technology given by
richer countries to poorer ones, either to help
with an emergency or to encourage long-term
development.
Monitoring and Predicting Volcanoes
• Frequency and strength can be recorded and
historical records kept.
• Volcanologists can monitor the records and look
for patterns.
• Tiltmeters can measure changes in slope angles
• Surface temperatures can be monitored
• Digital cameras can record if left in crater
• Gases emitted can be measured
• Robots called ‘spiders’ can monitor lava flows,
ash movements
Supervolcanoes
• Key words: supervolcano, caldera, fissure,
geothermal, geyser, hot spot.
• One example is Yellowstone National Park,
USA
• They release over 1000km cubed of material.
• Do not look like volcanoes.
• They are large depressions called CALDERAS.
They often have rims of higher land.
Yellowstone – a worrying future!!
• An eruption would destroy 10,000km squared of land, kill 87,000
people, 15 cm of ash would cover buildings within 1000km. Ash
would affect transport, electricity, water and farming.
• Magma beneath Yellowstone is shifting. The caldera is bulging
beneath Lake Yellowstone! The ground has risen by up to 70cm!
The magma chamber is believed to be 80km long and 40km wide
and 8km deep!
• Watch out! There have been eruptions 2 million years ago, 1.3
million years ago and 630,000 years ago!
• Tourists love to visit Yellowstone National Park. They go a see Old
Faithful – this is a Geyser. Google it! Check it out. Old Faithful
releases pressure deep underground.
Earthquakes
• Key words: earthquake, focus, epicentre,
shock waves, aftershocks, Richter scale,
Mercalli scale. Make sure you learn their
meanings!
Measuring Earthquakes
• We can measure earthquakes using the:
1) Richter scale (measurements created by
seismographs)or 2) Mercalli scale
(description of damage)
Richter Scale
Mercalli Scale
No upper limit of scale
Uses scale from I to XII (1-12)
It is logarithmic (10 times as strong
from 1 to 2).
Uses descriptions for each scale of the
resulting damage.
Richter scale 2 is 10 times stronger
than Richter scale 1. Richter scale 3 is
100 times stronger than Richter scale
1.
XII – Total destruction, objects thrown
in air, land rolling like waves
I – Barely felt
VI – Felt by everyone, some
frightened, chimneys break, furniture
moves, slight damage.
Earthquakes in LEDC’s and MEDC’s
• What are the causes, effects and responses to
earthquakes? How are they different in
LEDC’s/MEDC’s?
• The next slides give you 2 case studies for this!
Earthquakes! Safety net case studies
KOBE, Japan, MEDC
SICHUAN, China, LEDC
0546hrs 17th January, 1995
1428hrs 12th May, 2008
CAUSE: Philippines plate shifted
underneath Eurasian plate. Along Nojima
fault line underneath Kobe city.
CAUSE: Indian plate collided with Eurasian
plate. Along Longmenshan fault line
underneath Sichuan provence.
Earthquake triggered: 7.2 on Richter
Scale, tremors lasting 20 seconds
Earthquake triggered: 7.9 on Richter
Scale, tremors lasting 120 seconds
EFFECTS: Deaths 6434. Injured 40,000.
300,000 homeless. Gas mains ruptured in
city. Water pipes burst. Bridges collapsed.
Railway lines buckled. 30% trains from
Kobe city to Osaka were running
afterwards. 2 million homes without
electricity. 1 million without water for 10
days. Fires broke out west of the port and
damaged roads made it difficult to put
them out. People gathered in tents in
park areas.
Cost: $220 billion but economy suffered
and large companies such as Panasonic
were temporarily forced to close.
EFFECTS: Deaths 55,000 after 11 days,
69,000 two months later with 18,000
people missing. 374,000 injured. 5 million
homeless. In rural areas near the
epicentre, 80% of buildings collapsed. 5
million buildings collapsed. Juyuan school
collapsed killing 900 students.
Communication failed – neither mobile or
land lines worked. Roads blocked by
landslides. Rivers blocked by landslides
leading to fears of flooding. Cost: $75
million!!
Responses to Earthquakes:
• KOBE: Emergency services searched through rubble. Hospitals did what
they could, treating and operating in corridors!! Shops provided water and
essentials free of charge. Railways were 80% operational within a month.
After a year, the port was 80% operational. Buildings built to a 1981 code
survived, buildings built in 1960’s collapsed. New buildings were built
further apart so that they didn’t collapse onto each other in future.
Rubber blocks were fitted under bridges to absorb shock.
• SICHUAN: Some areas not reached within 30 hours of the quake. 20
helicopters were used for search and rescue. Troops parachuted in to help.
Others hiked on foot. Army deployed – thousands of troops. Immediate
needs were water, food, shelter. 3.3 million tents needed. China requested
international help. Teams from Russia and Japan arrived. Cash donations
were welcomed. Red Cross raised £100 million in the 2 weeks after the
quake. 1,000,000 small homes were built. Medicine, shelter, food, water
distributed. $10 million rebuilding fund set up. Banks wrote off debts
owed by survivors who did not have insurance.
The 3 P’s
These provide the key to REDUCING THE IMPACT of
earthquakes.
Prediction – forecast when and where tremors will
happen based on current knowledge – this is
VERY difficult to do.
Protection – building using appropriate standards
and designs so that they are safe to be in.
Preparation – ensure that hospitals, emergency
services and residents practise having disasters.
Organising activities and drills.
Earthquake proof buildings...
• Steel frames can sway
during movement
• Specialised flexible
glass
• Deep foundations
• Rubber shock
absorbers
• Roads to allow quick
evacuation
• Fire-resistant
materials
• Open areas to
evacuate to.
Tsunamis
• Triggered by earthquakes
• Primary effect – shifting of plates
• Secondary effect – displacement of ocean
water
• 200km from crest to crest whereas normal
waves are as follows:
Tsunamis
• “A special type of wave where the entire
depth of the sea or ocean is set in motion by
an event, often an earthquake, which
displaces water above it and creates a huge
wave”.
• Move at speeds of up to 800km per hour.
Japan Earthquake 2011 Facts to learn:
• Date 9th March, 2011
• Earthquake was magnitude 8.9 on the Richter scale – largest on
record!
• Earthquake struck about 250 miles (400km) from the capital Tokyo
and at a depth of 20 miles.
• Plates – Pacific plate subducting underneath Eurasian plate near
Honshu
• The earthquake caused major damage in Tokyo but triggered a
tsunami which devastated the Sendai region.
• A 30 foot wall of water hit the coast in places.
• Over 2400 killed with the number still rising.
• Thousands of homes and business destroyed.
• The city of Sendai is a scene of widespread devastation.
Japan Earthquake, 2011
Locating it!
Plate
Tectonics!
It struck about 250 miles (400km) from the capital at a depth of 20 miles. There have been
powerful aftershocks. The PACIFIC PLATE COLLIDED WITH THE EURASIAN PLATE.
Effects – Short Term
Kyodo news agency said a 10-metre wave (33ft) struck the port of Sendai in Miyagi
Japanese television showed cars, ships and even buildings being swept away by a vast wall of
water after the 8.9-magnitude earthquake.
The quake has sparked fires in several areas including Tokyo, with at least 15 people reported
dead.
Effects – Short Term
Effects – Short Term
Effects – Short Term
In central Tokyo, Jeffrey Balanag said he was stuck in his office in the Shiodome Sumitomo
building because the elevators had stopped working.
Effects – Short Term
Kyodo said at least
15 people had been
killed in the
earthquake and
tsunami. It was
believed the death
toll could rise
significantly.
Effects – Short Term
Emergency response headquarters have been
set up.
Effects – Short Term
The earthquake also
triggered a number of
fires, including one at an
oil refinery in Ichihara
city in Chiba prefecture
near Tokyo, engulfing
storage tanks.
Effects – Short Term
20 people injured in Tokyo after the roof of a hall collapsed
Effects – Short Term
Residents and workers in Tokyo rushed out of apartment buildings and office blocks and
gathered in parks and open spaces as aftershocks continued to hit.
Effects – Short Term
Bullet train services to northern Japan were halted, rapid transit in Tokyo was suspended
This man was found floating on the roof of his house 10 miles out to sea. He
had been there for 2 days.
The Japanese Prime Minister needed
to respond...!
Easy to remember short term
responses...Level 1 and 2
•
•
•
•
•
•
•
Clear roads
Ask for military help
Clear debris
Warn hospitals
Send rescue teams to the worst affected areas
Prepare people for aftershocks
Demand help or AID from other countries
Other Short term responses...Level 3
• Rescue services and emergency services were swamped by the scale of
the disaster.
• 2000 bodies were found on a beach – controlling disease became vital.
There was a race to identify the dead bodies.
• Fresh water, water purification tablets, food, bedding and tents poured in
as AID.
• UK and US governments offered financial support – International Aid
• Medical teams gathered in emergency centres to care for sick and injured.
• Missing Person Centres were set up by volunteers.
• A nuclear power station needed to be ‘cooled’ rapidly to stop a major
nuclear disaster as it was damaged during the earthquake.
• Fires needed to be put out where possible. Some buildings were on fire in
Tokyo due to the earthquake. Gas explosions, fires causes by leaking water
pipes on electrical wires.
Long Term Responses
1) Continue to improve the early warning
system – alarms did go off in Tokyo.
2) Re-build Sendai area with help from
international community
3) Re-open schools and hospitals
4) Strengthen buildings near coastline in case of
further tsunamis
There was less devastation than the
Asian Tsunami 2004 because...
1) There is less tourism in Sendai...so there were
fewer hotels and buildings along the coastline
2) JMA (Japan Meteorological Society) earthquake
early warning system – this gave Japan valuable
minutes to prepare
3) Japan is more developed and has been able to
spend more money on better building standards
– some of which are earthquake proof!