Year 10 living in an active zone revision powerpoint

3. The crust is similar to
the shell of a
cracked egg, and is made
up of large
plates of rock.
Underneath, the
mantle is made up of
molten rock.
The plates move slowly
due to
convection currents.

4. Plate
Names
African Plate
Indo Australian Plate
North American
South American
Eurasia
n
Pacific
Nazca
Antarctic

5. • A destructive plate margin is where two
plates are moving towards each other.
• The point where the two plates meet is called
the subduction zone.
• One plate is forced beneath another into the
mantle.
• This can lead to the formation of features
like oceanic trenches and volcanic fold
mountains.
•http://www.absorblearning.com/media/item.action?quick=12s
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

6. At a constructive plate boundary, two
plates move apart. As the two plates
move apart, magma rises up to fill the
gap. This causes volcanoes at this type
of boundary. However, since the magma
can escape easily at the surface the
volcano does not erupt with much
force. Earthquakes are also found at
constructive boundaries.
An example of a constructive boundary
is the Mid-Atlantic Ridge.
Sometimes plates pull apart beneath the
sea. Magma wells up and cools to form
new crust. This leads to a ridge being
developed such in the Atlantic ocean
where the Mid-Atlantic ridge is found.
Earthquakes can also take place.

7. Constructive plate boundaries
can also be found on land. The
Plates can pull apart to leave a
rift valley with steep sides.
This has happened in Iceland
along the Mid-Atlantic ridge to
form the Thingvellir rift valley

8. These are low, broad
volcanoes and are produced
by runny lava that flows
over a large area.
These volcanoes can be
very large and ash can
build up around their vents
to leave a cinder cone.

9. These are steep sided,
made by layers of ash
and lava, high summit
(top) and explosive
volcanoes

11. Primary
Hazards
Secondary
Hazards
These happen because of a change in
the environment following an
earthquake or eruption
These happen as a direct result of the
earthquake or volcanic eruption

12. • Lava flows are usually slow but can destroy
buildings, roads and trees.

13. • Pyroclastic flows – A landslide of hot
ash, rocks and gases from a violent
eruption.

14. • Lahars or mudflows are produced when ash
or mud mixes with rainwater. These can have
very serious consequences.

15. • Ash – Powdered rock fragments that are
thrown from a volcano during an explosive
reaction

17. Mt St HelensBEFORE
AFTER

19. Mt St Helens
Consequences of the Eruption
N
O 10km

20. Hot mudflows raise the temperature
of the rivers and lakes to 30ºC.
Two million birds, animals and fish are killed.
60 people die from
the eruption.
Mudflows block and divert rivers. The US army takes
18 months to dig out the debris from the River Toutle.
Communications routes threatened – railway and
road bridges destroyed, Portland harbour blocked
Gophers, through their
tunnelling, mix the soil with
the ash. This increases
the fertility of the soil.
An
increase in
tourism
Deer mice,
chipmunk, vole,
gophers, salamander
survive the blast.
Their population
steadily increases
due to the absence
of predators.
A decrease in
tourism
What benefits might the volcanic activity have brought to Mt St Helens?
Damage to crops=$175million
The post office
and Lone Fir Motel
shut down in
Cougar.
Up to 70mm of ash falls across Washington and
East Montana…7000 students have an early
Summer vacation due to problems on the roads

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

23. • Buildings, roads and pipelines can break due
to the intense ground shaking.

24. • Strong aftershocks can cause more damage
and restrict rescue efforts.

25. • Marshy soil can lose its strength and become
very soft ( like wet concrete) when violently
shaken. This causes the foundations of
buildings to collapse.

26. • A tidal wave that is created when an
earthquake occurs.

27. • In built up area this is major threat straight after an
earthquake. Broken gas pipes can ignite and fires
can be quickly spread.

28. • Soil, rock and mud can move quickly downhill,
blocking road and rail links.

29. • The Richter Scale is the best known scale for measuring the
magnitude of earthquakes. It is logarithmic. A recording of 7,
for example, indicates a disturbance with ground motion 10
times as large as a recording of 6.
• A Seismograph which is used to measure the size of an
earthquake. The needle moves as the ground shakes and the
ink moves across the page to record the size = bigger shake –
bigger line!!

30. Sometimes snakes and animals behave oddly before
volcanic eruptions. There have been observations of this
in places like Asia.
The ground often changes shape. For example, at Monserrat
the lava dome swelled in size in the weeks leading up to 28th
July 2008 ( use tilt meters)
This is a sure sign that volcanic activity going to happen. As
the magma moves up the volcano pressure is put upon the
volcano, causing cracks and small earthquakes to occur. May
lead to rockfalls
If there is a steady increase of sulphur dioxide, this shows
there is likely to be an eruption. This shows magma is rising
to the surface.

31. 1) Development of Observatories, eg Montserrat Volcano
Observatory (MVO), collect data on a particular volcano
2) Monitoring Stations placed around volcano, powered by solar
panels
3) Seismographs measure even the smallest tremor in the earth’s
surface, which trigger warnings for towns and cities
4) Global Positioning Systems (GPS) satellites are used to record
even the slightest change in the shape of the volcano
5) Tilt meters are used to measure larger changes in the surface
of the ground
6) Radar and Aerial Photographs can be used to record changes
in shape
7) Remote sensing satellites can be used to detect changes in
heat / temperature of rock surfaces indicating magma rising to
the surface.

32. THINK
Short Term or Long Term

33. Responses to the Earthquake
The Chinese government responded
quickly and provided 50,000 troops to help
the relief effort.
In the first few days rescuers had to sift
through rubble with their hands.
Large heavy earth-moving equipment had
to be brought in from over seas.
Expertise from Japan was needed.
Temporary camps were set up.
http://news.bbc.co.uk/1/hi/world/7397838.stm
All Short Term

34. Many residents and rescuers first used
their bare hands to clear the debris from
collapsed buildings.
Local emergency services were quickly on
the scene. The army helped to rescue
victims.
In L'Aquila, 95km (60 miles) north-east of
Rome, over 3000 buildings in the medieval
city were damaged.
A university dormitory, churches and a
bell tower are believed to be among the
buildings that had collapsed.
Local medical facilities were used and a
field hospital were set up. http://news.bbc.co.uk/1/hi/world/europe/7984867.
All Short Term

35. http://news.bbc.co.uk/1/hi/world/7397838.stm
Spraying lava with water to cool it
and solidify it.
Earth barriers have been used to
channel the direction of lava flow.
Dropping concrete blocks via
helicopter to divert the flow.
Aerial bombing lava tubes with
dynamite to widen them and
reduce the flow.
All Short Term

36. Now Think Long Term !!
This is section is about the
Three Ps – Plan, Predict and Prepare
1) Planning - a) using strict planning laws to control where
areas of new development so that less buildings are in
dangerous areas, b) design and create buildings to with stand
the effects of earthquakes and minimise damage, c)
|Emergency services with specialist teams trained to react to
an event;
2) Predict – use technology to predict when hazard may
occur ( see slide above) but think Early Warning Systems,
Tsunami ocean buoys use to monitor size of waves and
predict when wave hits land;
3) Prepare people to react to the effects of an earthquake /
volcano – education in schools (earthquake drills) and TV /
Radio on what to do – think Tsunami warnings in Japan;