Transcript Volcanic eruptions - 2015-Sec3-Geog

CHAPTER 2
LIVING WITH
TECTONIC HAZARDS
Risk or Opportunity?
CHAPTER 2 LIVING WITH
TECTONIC HAZARDS
In this Chapter, you will explore three key
questions:
1.Why are some areas more prone to tectonic
hazards?
2.What landforms and associated tectonic
phenomena are found at plate boundaries?
3.How do people prepare for and respond to
earthquakes?
CHAPTER 2 LIVING WITH
TECTONIC HAZARDS
Gateway 2: What landforms and associated
tectonic phenomena are found at plate
boundaries?
The sea started to recede. I remember
learning in a geography lesson that this
happens before a tsunami. I shouted to tell
everyone a tsunami was coming and for
them to run!
Quoted from a survivor of the tsunami that took place at Mai Khao
Beach , Thailand on 26 December 2004.
Gateway 2: What landforms and associated
tectonic phenomena are found at plate
boundaries?
In December 2004, The Tsunami swamps Phuket's Chedi resort (AFP/Joanne Davis)
After the tsunami, authorities have now
installed signs along this coastline.
• What symbols and words would you expect to
see on these signs. Sketch the signs you
expect to see at the beach.
• Explain why you thought the signs are
important.
CHAPTER 2 LIVING WITH
TECTONIC HAZARDS
Gateway 2: What landforms and associated
tectonic phenomena are found at plate
boundaries?
a.Why are different landforms found at different plate
boundaries and how are they formed?
b.What phenomena are found at plate boundaries and how are
they formed?
a. Why are different landforms found at
different plate boundaries and how are they
formed?
• The movement of plates at different plate
boundaries can result in various landforms such as:
- Fold mountains
- Rift valleys and block mountains
- Volcanoes
Fold mountains
•
http://www.bbc.co.uk/science/earth/surface_and_interior/mountain_formation#p00fzsnd
• Over millions of years, the folding of rocks creates a
landform called fold mountains.
• The Himalayas, the Rocky Mountains and the Andes
are examples of fold mountains.
Fold mountains
• Fold mountains are formed along convergent
plate boundaries.
• The compressional force causes the layers of
rocks to buckle and fold.
• This process is known as folding.
Fold mountains
• The upfold is called the anticline and
• The downfold is the syncline.
• When there is increasing compressional force on one
limb of a fold, the rocks may buckle until a fracture
forms.
• The limb may then move forward to ride over the
other limb
Fold mountains
The Himalayas
Peak : Mount Everest (between
Nepal and Tibet)
Elevation : 8,848 metres
Fold mountains
• Fold mountains are located along convergent plate
boundaries
• Fold mountains are found along the western
coast of North, Central, South America and
the Aleutian islands
• The other zone starts from Japan to
Philippines and all the way to New Zealand
• The third zone stretches across the
Mediterranean region, across Turkey, Iran,
Iraq, India and South East Asia.
• Convergent plate boundaries (give eg)
Rift valleys and block mountains
• Rift valleys and block mountains are formed at
divergent plate boundaries.
Rift valleys and block mountains
• A fault is a fracture in the rocks along which
the rocks are displaced.
• The tensional forces result in parts of the
crust being fractured.
• This process is called faulting.
Rift valleys and block mountains
• A rift valley is a valley with steep sides formed along
fault lines.
• E.g. East African Rift Valley
Rift valleys and block mountains
• A block mountain is a block of land with steep sides.
It is formed when sections of the crust extend along
fault lines and rock masses surrounding a central
block sink due to tensional forces.
Rift valleys and block mountains
The East African Rift Valley
Is formed from the Nubian
section of the African Plate and
the Somalian section of the
African Plate pulling away from
one another.
Rift valleys and block mountains
• Distribution of rift valleys and block mountains
Volcanoes
• A volcano is a landform formed by magma ejected
from the mantle onto the earth’s surface.
Mount Saint Helens volcano before and after an eruption in May
1980 (what is the difference?)
Vesuvius
http://www.youtube.com/watch?v=jN5hW3OlZi
Q&feature=youtu.be
Volcanoes
• Magma is molten rock found below the earth’s
surface.
• Parts of a Volcano
- magma chamber
- vents
• Magma that is ejected onto the surface is known
as lava.
Volcanoes
Formation, structure of, and features of a volcano
Volcanoes
• Volcanoes vary in shapes and sizes due to the
characteristics of the lava.
– Viscosity refers to the stickiness of the lava
– Silica content (low silica – basic lava: high silicaacid lava)
– Amount of gases trapped
• The most common types of volcanoes are:
- Shield volcanoes; and
- Stratovolcanoes
Volcanoes
Shield volcanoes
• Shield volcanoes have gently sloping sides and a
broad summit (lava type? Type of plate boundary?)
• E.g. Mount Washington, United States of America
Volcanoes
Stratovolcanoes
• Stratovolcanoes develop from successive eruptions
of lava and ash. (lava type? Plate boundary?
• E.g. Mount Mayon, Philippines
Distribution of earth’s major active volcanoes
• Along Plate boundaries
• Pacific Ring of Fire(converging plates)
• Atlantic Ocean, East Africa (divergent plates)
Ten Most Active Volcanoes
• http://youtu.be/4aYQixhdWY4
• https://www.youtube.com/watch?v=AhSaE0o
mw9o (hot spots)
b. What phenomena are found at plate
boundaries and how are they formed?
Earthquakes
https://www.youtube.com/watch?v=OiWaqNTL2CM
An earthquake is a vibration in the earth’s crust caused
by the sudden release of stored energy in the rocks
found along fault lines.
Earthquakes
• Extent of earthquakes
- The Richter Scale is used to measure the magnitude
of an earthquake
Earthquakes
• Apart from its magnitude, the extent of damage
caused by an earthquake may vary based on other
factors:
-
Population density
time of occurrence
level of preparedness
distance from the epicentre
type of soil
Earthquakes
The distribution of the earth’s major earthquakes
Location of major earthquakes
• Along the Pacific Ring of Fire
• Along the Mid-Atlantic Ridge
• Stretching across from western Europe to
Central Asia, north India, China, Southeast
Asia
• Stretching across the north American
continent
• …………
• At all types of plate boundaries
• Most frequent at convergent plate boundaries
• But some may be a distance from plate
boundaries, eg Sichuan quake in 2008
Earthquakes
• Measuring earthquakes
- A seismograph records the seismic waves released
by an earthquake.
Earthquakes
Hazards associated with living in earthquakes zones
- Threat of tsunamis
- Disruption of services
- Fires
- Landslides
- Destruction of properties
- Destruction of infrastructure
- Loss of lives
Hazards associated with earthquakes
Threat of tsunamis
• Tsunami refers to an usually large sea wave.
• Tsunamis may be formed by:
- The movement of the sea floor during a large earthquake
at subduction zones;
- An underwater volcanic eruption;
- An underwater landslide; and
- A landslide above sea level which causes materials to
plunge into the water.
Hazards associated with earthquakes
Hazards associated with earthquakes
• In 2004, a 9.2 magnitude triggered a tsunami with
waves spreading throughout the Indian Ocean.
Aceh before and after the tsunami hit the area
Hazards associated with earthquakes
The spread of the tsunami waves caused by the tsunami
Hazards associated with earthquakes
Disruption of services
• An earthquake can disrupt services such as the
supply of electricity, gas and water.
• The earthquake in Kobe, Japan, in 1995 disrupted
electricity, gas and water supplies to about a million
of Kobe city’s 1.4 million residents.
Hazards associated with earthquakes
Fire
• Earthquakes may rupture gas pipes and this can
provide fuel to start fires.
• For example, the earthquake in Kobe, Japan, in 1995
caused extensive fires.
Hazards associated with earthquakes
Landslides
• Landslides are rapid downslope movements of soil,
rock and vegetation.
• Mudflows may also occur when there is heavy
rainfall.
Hazards associated with earthquakes
Destruction of properties
• Earthquakes can cause destruction to many homes.
• People may be without homes after the disaster.
Hazards associated with earthquakes
Destruction of infrastructure
• Earthquakes may cause cracks to form in
infrastructure such as roads and bridges.
• Transportation can be disrupted as it is unsafe to use
the damaged roads.
Hazards associated with earthquakes
Loss of lives
• Earthquakes and their associated hazards often
threaten the lives of those living in earthquake zones.
Hazards associated with earthquakes
b. What phenomena are found at plate
boundaries and how are they formed?
Volcanic eruptions
- Occurs on land occur on the sea floor.
Active, dormant or extinct
• Active volcanoes refers to volcanoes which are currently
erupting or are expected to erupt in the future.
• Dormant volcanoes are currently inactive but may erupt
in the near future.
• Extinct volcanoes refers to volcanoes without current
seismic activity
Volcanic eruptions
Risks of living near volcanic areas
Some of the risks associated with living near volcanic
areas include:
• Destruction by volcanic materials
• Landslides
• Pollution
• Effects on weather
Volcanic eruptions
Destruction by volcanic materials
• Volcanic materials can lead to widespread damage of
property.
Volcanic eruptions
Landslides
• Landslides can occur due to the structural collapse of a
volcanic cone.
• Obstruct the flow of rivers which causes floods,
• block roads, and
• bury villages and farmlands.
Volcanic eruptions
Pollution
• Ash particles may block sunlight, suffocate crops, and
cause severe respiratory problems for people and
animals.
• Release of gases may be harmful to people.
Volcanic eruptions
Volcanic eruptions
Effects on weather
• Sulphur dioxide released from volcanic eruptions
has impacts on the environment
• It may react with water vapour and other
chemicals in the atmosphere to form sulphurbased particles.
• These particles reflect the sun’s energy back into
space and temporarily cool the earth for periods
of time.
Volcanic eruptions
Benefits of living near volcanic areas
• Fertile volcanic soil
• Building materials, and precious stones and
materials
• Tourism
• Geothermal energy
Volcanic eruptions
Fertile volcanic soil
• Lava and ash from the volcanic eruptions break
down to form fertile volcanic soils.
• Favourable to agriculture
Volcanic eruptions
Precious stones and minerals, building materials
• Volcanic rocks can be rich in precious stones and
minerals.
• These resources can only be from a volcanic area
after millions of years.
• An example is diamond.
Volcanic eruptions
Tourism
• Volcanic areas offer a variety of activities for
tourists to engage in.
• The ruins of Pompeii, Italy, is one such example.
Volcanic eruptions
Pompeii was partially destroyed and buried under 4
to 6 m (13 to 20 ft) of ash and pumice in the
eruption of Mount Vesuvius in CE 79.
Volcanic eruptions
Geothermal energy
• Geothermal energy is derived from the heat in the
earth’s crust.
• The hot water or steam can be harnessed to produce
electricity.
CHAPTER 2 LIVING WITH
TECTONIC HAZARDS
Gateway 2: What landforms and associated
tectonic phenomena are found at plate
boundaries?
a. Why are different landforms found at different plate
boundaries and how are they formed?
b. What phenomena are found at plate boundaries and how are
they formed?