Transcript The Restless Earth - Heathcote School & Science College

The Restless
Earth
Year 11 revision
Key terms
Key term
Definition
Asthenosphere The upper part of the Earth’s mantle, where
the rocks are more fluid.
Collision plate
boundary
A tectonic margin at which two continental
plates come together (collide).
Conservative
Where two tectonic plates slide past each
plate boundary other.
Constructive
Tectonic plate margin where rising magma adds
plate boundary new material to the diverging plates.
Destructive
Tectonic plate margins where oceanic plate is
plate boundary subducted.
Convection
currents
Circulating movements of magma in the mantle
caused by heat from the core.
Key terms
Key term
Definition
Core
The central part of the Earth, consisting of a
solid inner core and a more fluid outer core, and
mostly composed of iron and nickel.
Evacuation
The removal of people from an area, generally in
an attempt to avoid a threatened disaster (or
escape from one that has happened).
Long-term
planning
Planning that takes into consideration the long
term (i.e. over 5 years).
Oceanic crust
The part of the crust dominated by denser
basaltic rocks. (Under oceans)
Continental
crust
The part of the crust dominated by less dense
granitic rocks. (Under continents)
Key terms
Key term
Definition
Tectonic
hazards
Threats posed by earthquakes, volcanoes and
other events triggered by crustal processes.
Plate margin
The boundary between two tectonic plates.
Prediction
Forecasting future changes.
Primary
impacts
Impacts caused directly by the
volcano/earthquake.
Secondary
impacts
Impacts caused indirectly by the
volcano/earthquake, for example ‘a knock on
effect’ e.g. Fires caused by broken gas pipes.
Response
The way and which people react to a situation.
Short-term
emergency
relief
Help and aid provided to an area to prevent
immediate loss of life because of shortages of
basics, such as water, food and shelter.
Key terms
Key term
Definition
Focus
The point inside the earth where an earthquake
starts.
Epicenter
The point on the lands’ surface, directly above
the focus.
Seismic waves Waves of energy that radiate out from an
earthquake.
Magnitude
The size of an earthquake, measured by the
Richter Scale.
Key facts: Structure of the Earth
Key facts: The crust
Oceanic Crust
Continental
Crust
• On land
• Thicker
(30-65km)
• Underneath
oceans/seas
• LIGHT Granitic
rock
• Thinner
(8-12km)
• (rich in Si, Al)
• HEAVY Basaltic
rock
• (rich in Si, Mg)
Mantle
Key facts: Tectonic plates
Key facts: Constructive plate boundary
Magma rises between the
plates, forming volcanoes
North American plate
Plates are pulled apart by the
convection currents in the
mantle below
Eurasian Plate
e.g. The mid-Atlantic Ridge (Eurasian and North
American plates moving apart)
Key facts: Destructive plate boundary
e.g. Nazca is
subducting
under South
American
plate.
Heavier oceanic crust
gets pushed under the
continental plate
Lower mantle
The rock jolts and grinds,
causing earthquakes
The area where the
oceanic plate sinks below
the continental plate is
called the SUBDUCTION
ZONE
The movement heats up
the rock and melts it. The
molten rock forces its way
up through the crust to
form a volcano.
Key facts: Conservative plate boundary
e.g. San Andreaas Fault in California, USA.
(North American and Pacific plates sliding past
each other)
Plates slide
past each
other. Parts
of the plates
get stuck and
then lurch
free causing
earthquakes.
No rock is pushed down or melted and no gaps occur
between the plates therefore there are no volcanoes.
Key facts: Collision plate boundary
The rock jolts and
grinds, causing
earthquakes
Two continental crusts
move towards each other
The plates neither
sink or
are destroyed – so
they buckle
upwards forming
mountains
e.g. The Himalayas (Nepal).
Formed as the Indian and
Eurasian continental plates
push into each other
Key facts: Hazards at plate margins
Asia
North
America
Europe
Africa
Australasia
South
America
Key:
Volcano
Earthquake
Key facts: Convection currents
Circulating movements of magma in the
mantle (convection currents) caused by
heat from the core
Case studies!
Volcano Case Study 1:
Type: Composite volcano
Name: Mt St. Helens, USA
Volcano Case Study 1:
Type
Composite volcano
Name
Mt St. Helens
Location
Washington State, USA. On the plate boundary
between the Juan de Fuca plate and North
American plate.
Formation
Layers of lava and ash are deposited by eruptions.
The lava is....
Lava type
...mostly andesitic, which typically cools and
hardens before spreading far due to high
viscosity (thick like honey!), leading to...
Shape
...a steep-sided volcano.
Explosivity/
pyroclastic
flows
Highly explosive with lots of boulders and debris.
Nuée ardente (hot ash and gas), Lahars (mudflows
of ash and water).
Volcano Case Study 1:
Mount Saint Helens
Date: 18th May 1980
Type: Composite volcano
Primary effects:
• 57 fatalities, 200 houses, 27
bridges, 15 miles of railway and 185
miles of roads were destroyed
• Ash cloud reached 80,000ft in 15
minutes, circled the earth in 15 days
• The eruption removed 13% of the
volcano’s rock, making it 390m
shorter
• Thousands of Elk, Deer and Salmon
were killed and crops were
destroyed
Secondary effects
• Major problems with sewerage
disposal and water systems
• Roads closed due to low
visibility from the ash
• Some airports closed for two
weeks
• Fine ash getting into electrical
systems caused blackouts
• 5 further eruptions between
May and October 1980
Volcano Case Study 2:
Type: Composite/Fissure volcano
Name: Mt Nyiragongo.
Volcano Case Study 2:
Type
Composite/Fissure volcano
Name
Mt Nyiragongo
Location
Democratic Republic of Congo (Africa)
Formation
Layers of lava have erupted from the crater
and fissures. The lava...
Lava type
...has an extremely low silica content (the lava
is mafic) and so flows very fast (can reach
100km/h), meaning...
Shape
...the volcano has very steep sides as the lava
flows away so quickly
Explosivity/
pyroclastic
flows
Low explosivity but fast-moving lava poses
great danger. CO2 gas released. Ash clouds
occur.
Volcano Case Study 2:
Mt Nyiragongo, Democratic Republic of Congo
Date: 17th January 2002
Type: Composite / Fissure volcano
Primary effects:
• Homes were destroyed by ash and
lava
• 100 people died
• Lava filled roads making it difficult
for emergency services to move
around
• Lava covered 15% of Goma city, and
destroyed 30% of the city
Secondary effects
• 400,000 people evacuated
• Cholera spread because of poor
sanitation
• One month after the eruption,
350,000 people were dependant
on aid
• People lost their businesses and
jobs
• After the eruption, a large
number of earthquakes were
felt around Goma and Gisenyi
Volcano Case Study 3:
Type: Shield volcano
Name: Mauna Loa, Hawaii.
Volcano Case Study 3:
Type
Shield volcano
Name
Mauna Loa
Location
Hawaii (on the ‘Hawaii Hotspot’)
Formation
Mauna Loa was created as the Pacific
tectonic plate moved over the Hawaiian
hotspot in the mantle. Fluid lava flows
out slowly from the volcano because...
Lava type
...the lava is mostly basaltic, silica-poor,
and very fluid. This creates...
Shape
...a low and flat shape
Explosivity/
pyroclastic flows
Low, non-explosive.
Volcano Case Study 3:
Mauna Loa, Hawaii
Date: 24th March, 1984
Type: Shield volcano
Primary effects:
• Potential impact to the city of Hilo,
though lava from the 1984 eruption
did not impact the city
• In the 1950 eruption, lava reached
the sea within 4 hours of the
eruption and destroyed a village
Secondary effects
• There has only been one
recorded fatality from
eruptions of Mauna Loa
Earthquakes
Earthquake Case Study 1: San Francisco
Name: San Francisco, USA
(MEDC)
Date: 17th October, 1989
Why:
• California sits near the
San Andreas fault
• The Pacific and North
American plates slide
past each other
• The fault slipped several
metres
San
Andreas
Fault
Earthquake Case Study 1: San Francisco
Property
cost $10
billion
Clay soils liquefied, causing
houses to sink, gas pipes to
burst  fires broke out
Facts
12,000
homeless
Death toll would have been larger, but
2 big baseball teams playing so many
people where at the stadium or
already at home, not commuting.
Nearly
4,000
injured
63 dead
Hit
during
rush
hour
Earthquake Case Study 1:
San Francisco, USA
Size: 6.9 on Richter Scale
Primary effects:
• 63 fatalities, 3,757 injuries and
12,000 homeless
• Upper deck of Freeway collapsed
onto lower deck, causing 42
fatalities
• 1.4 million people without power
following the earthquake, restored
to most the same day
Secondary effects
• Burst gas mains leading to
multiple fires
• Soil liquefaction causing major
property damage
• Landslides and ground ruptures
• 1.4 million people without power
following the earthquake
Earthquake Case Study 2:
Name: El Salvador, Central
America (LEDC)
Date: 13th January and 13th
February, 2001
Facts:
• Smallest country in
Central America with
less people than London.
• Very seismically active
area, at the junction of
three tectonic plates
What happened?:
Two major earthquakes
within 1 month, plus
thousands of aftershocks
Earthquake Case Study 2:
El Salvador
is a very
poor LEDC
Even where fire-engines
are available there is no
water supply for them to
use or good roads to reach
the areas in need.
>1.5million
people
affected
Buildings and roads
are not usually
designed to withstand
earthquakes here
Roads and
other
infrastructure
poor (as LEDC)
Facts
Over
8,000
injuries
Less equipment/
training for
emergency services
(LEDC) so response
effectiveness
reduced.
185,338
houses
damaged
Emergency
services, such as
hospitals and
the fire service,
are not wellprepared to deal
with a largescale disaster.
Earthquake Case Study 2:
El Salvador, Central America
Size: 7.6 / 6.6 on Richter Scale
Primary effects:
13th January earthquake:
• 844 fatalities, 4,723 injured,
108,226 houses destroyed
• Many of the fatalities and much of
the damage was caused by
landslides
13th February earthquake:
• 315 fatalities, 3,399 injured,
41,302 houses destroyed
Secondary effects
• More than 2,500 aftershocks,
causing additional damage
• More than 500 landslides
• Clean water and sanitation
became major issues
• Major disruption to electricity
supplies
• Damage to the telephone
system and the control tower
at the airport delayed incoming
relief from abroad
What factors
influence the
effects / impacts
of a hazard?
The type of
hazard
The place’s
vulnerability
to hazards
The ability or
‘capacity’ to
cope and
recover from
an event
Impacts of earthquakes
Factor
Why this affects the impact of an earthquake?
Distance from the
epicentre
The effects of an earthquake are more severe at its centre.
Size of quake
The higher on the Richter scale, the more severe the earthquake
is.
Level of development
(MEDC or LEDC)
MEDCs are more likely to have the resources and technology for
monitoring, prediction and response.
Population density
(rural or urban area)
The more densely populated an area, the more likely there are to
be deaths and casualties.
Communication
Accessibility for rescue teams.
Time of day
Influences whether people are in their homes, at work or
travelling. A severe earthquake at rush hour in a densely populated
urban area could have devastating effects.
The time of year and
climate
Influences survival rates and the rate at which disease can spread.
Preparing for earthquakes and volcanoes
1. Monitoring seismic waves
2. Earthquake proof buildings
3. ‘Grab bags’ containing essential items
e.g. Tinned food, bottled water, blanket
4. Training emergency services
5. Evacuation plans
6. Early warning systems
Aims:
a)Minimise loss of life
b)Minimise disruption of critical services
c)Minimise damage
Preparing for earthquakes and volcanoes
MEDC building design:
Bolting buildings to foundations and
providing support walls (‘shear walls’).
These are made from concrete and have
steel rods embedded inside to help
strengthen.
Walls reinforced and supported by
adding diagonal steel beams
(‘cross bracing’)
‘Base isolators’ act like shock absorbers
between building and foundations. Help
absorb some of sideways motion.
Deep foundations for skyscrapers
Gas and water lines specially reinforced
with flexible joints to prevent breaking
Preparing for earthquakes and volcanoes
LEDC building design:
Strengthening new buildings by:
- Removal of mud overlay on roof
- Add diagonal bracing to frame
LEDC building design:
Strengthening old buildings by:
- Use cement/sand mortar and
shaped stones in construction.
- Limit thickness of mud overlay
to 200mm
- Install ‘knee-braces’ to reinforce
the vertical/horizontal
connections
- Use straw roofs
(often timber as steel too expensive)
- install ‘through-stones’. Needs
training of local artisans (new skills)
- strengthening of wall corners,
using wire mesh and cement
overlay (although mesh not often
available in rural areas)
- install ring beam (band of concrete)
at roof level
- Pointing of exterior walls with
cement mortar
Long and short-term responses to
tectonic hazards
Short-term response
Long-term response
Emergency care
Damage proof buildings
Foreign/national aid
Education/training
Prepare emergency kits for
future quakes/eruptions
Permanent relocation
Evacuation procedures in
place
Evacuation plans and
websites to inform citizens
Goals of
disaster
management
Reduce, or
avoid,
losses from
hazards.
Assure
prompt
assistance
to victims.
Achieve
rapid and
effective
recovery.
Video revision:
1. Continental drift
2. So why do the plates move?
3. Structure of the Earth 1
4. Structure of the Earth 2
5. Why do volcanoes & earthquakes happen?
6. Volcano formation
7. Subduction
8. Shield volcano
9. Mt St Helens
10.Nyiragongo film
Past GCSE questions: A
1.
Describe one way a region affected by earthquakes can prepare
for this hazard. (2 marks)
2.
Using an example(s), describe the effects of earthquakes on
people and property. (4 marks)
3.
Suggest one reason why the number of deaths varies between
earthquakes. (2 marks)
4.
Give two reasons why developing countries are very vulnerable to
earthquake damage (2 marks)
5.
Give two reasons why some earthquakes are more powerful than
others (2 marks)
6.
For either an earthquake or a volcanic eruption you have studied,
describe the immediate responses (straight after the
earthquake) in managing its impact. (4 marks)
Past GCSE questions: B
7.
Describe how hazard resistant design can help reduce the impact
of earthquakes (4 marks)
8.
Explain how building design can help reduce the impact of
earthquakes (4 marks)
9.
Explain how earthquakes happen on destructive plate margins (4
marks)
10. Explain how volcanoes are formed on either constructive or
destructive plate boundaries. (4 marks).
11. For a named volcanic event, compare the primary and secondary
impacts (6 marks)
Past GCSE questions: C
12. Describe two hazards volcanic eruptions can create for people
(4 marks)
13. Explain how shield volcanoes are formed. (4 marks)
14. Describe the features of a shield volcano (2 marks)
15. Examine why the characteristics of volcanoes vary (6 marks)
16. Outline one difference between oceanic and continental crust
(2 marks)
17. Describe two differences between oceanic and continental crusts
(4 marks)
18. Draw an accurate labelled diagram of a destructive plate margin
(4 marks)
Good luck!