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Tectonic hazards and causes
- Plate boundaries
- Convergent
- Oceanic crust is denser than
the continental plate and so
when they converge the
oceanic plate is subducted.
Melting occurs 1000km below
the surface
- Earthquakes are common at the
Benioff zone where plates get
locked due to the pressure and
break after release.
- Philippines
- Samar Island
- Mount Mayon
- Bohol Island
- Samar Island
- Oceanic crust is denser than
the continental plate and so
when they converge the
oceanic plate is subducted.
Melting occurs 1000km below
the surface
- Divergent
- Pressure from rising magma leads to a doming
of the surface and the formation of a ridge.
- Close proximity of the surface and so the
pressure is easily released.
- Eyjafllajoekull
volcano,
Iceland
- Pressure from rising magma leads to a doming
of the surface and the formation of a ridge.
- Transform
- Haiti
- No magma is released or
destroyed and no new
crust is formed. Two
crusts move in the similar
direction.
- Haiti
- Collision
- Two continental plates
collide and can form
new mountains.
- Balochistan, Pakistan
- Two continental plates
collide and can form
new mountains.
- Hot spot
- Magma rises from the
asthenosphere even they may not
be necessarily close to a plate
boundary. If the crust is thin or
weak, the magma may escape.
- Magma rises from the
asthenosphere even they may not
be necessarily close to a plate
boundary. If the crust is thin or
weak, the magma may escape.
- Convergent
- What else causes tectonic hazards?
- Fracking
- Way of extracting methane from shale rock. A
mixture of water, sand and chemicals are
injected under high pressure. This process
triggers small earthquakes and explosions.
- Blackpool, UK
- Way of extracting methane from shale rock. A
mixture of water, sand and chemicals are
injected under high pressure. This process
triggers small earthquakes and explosions.
- Isostatic rebound theory
- Lithosphere can change shape and tend as a result of a heavy
mass (ice sheets). There is a point reached where the lithosphere
is supported. As a result of climate change (ice sheet melted), the
lithosphere can rebound as a result and produce small
earthquakes.
- Lithosphere can change shape and tend as a result of a heavy
mass (ice sheets). There is a point reached where the lithosphere
is supported. As a result of climate change (ice sheet melted), the
lithosphere can rebound as a result and produce small
earthquakes.
- Fracking
- What is the evidence for tectonic hazards?
- Continental drift
- Alfred Wegner (1912) -this 300 million years ago
was a single continent known as Pangea.
- Alfred Wegner (1912) -this 300 million years ago
was a single continent known as Pangea.
- Magnetic magma
- Molten lava is magnetic, when it is liquid, it
wants to align with poles, some rocks are aligned
opposite as the magnetic field has changed.
There are patterns (1000km) away symmetrically
suggests they were once together.
- Molten lava is magnetic, when it is liquid, it
wants to align with poles, some rocks are aligned
opposite as the magnetic field has changed.
There are patterns (1000km) away symmetrically
suggests they were once together.
- Continental drift
- What will happen in the future for tectonic
hazards?
- There is evidence that the Mediterranean is closing.
- Africa is colliding with Italy. This is
shown in Mt Stromboli as water
vapour is in the trapped gases.
- Africa is colliding with Italy. This is
shown in Mt Stromboli as water
vapour is in the trapped gases.
- Pangea Ultima
- There is evidence that the Mediterranean is closing.
- What is the deadliest tectonic hazard?
- January 1556 in Shaaxi, China.
There was a 8.0 magnitude
earthquake and 1 million deaths.
- The volume of deaths is because many people who
live in Shaaxi live in caves. As an earthquake
occurs, the caves are very soft and so the
shockwaves caused the caves to collapse.
- It may occur again as forty
million people live there now.
- January 1556 in Shaaxi, China.
There was a 8.0 magnitude
earthquake and 1 million deaths.
- What is the costliest tectonic hazard?
- Sendai, Japan 2011
- Direct loss of $210 million.
- Reconstruction of $244 billion.
- Sendai, Japan 2011
- Hazard profiles
- Frequency
- Volume of tectonic
hazards that occur in
an area.
- Volume of tectonic
hazards that occur in
an area.
- Magnitude
- The higher volume of
tectonic hazards, the lower
the magnitude because
there hasn't been a high
level of pressure build up.
- Intensity of the hazard.
- The higher volume of
tectonic hazards, the lower
the magnitude because
there hasn't been a high
level of pressure build up.
- Areal extent
- What is the widespread
extent effect of a tectonic
hazard?
- Volcanoes have a wider
areal extent because of
the lava expelled.
- Volcanoes have a wider
areal extent because of
the lava expelled.
- What is the widespread
extent effect of a tectonic
hazard?
- Areal reliability
- Duration
- Time taken for
the tectonic event
to take effect.
- Time taken for
the tectonic event
to take effect.
- Speed of onset
- Time taken for the tectonic event
to take effect.
- Time taken for the tectonic event
to take effect.
- Frequency
- What is the
difference between a
tectonic event,
tectonic hazard and
tectonic disaster?
- A tectonic event is a physical
occurrence that occurs as a
result of the movement of the
Earth.
- A tectonic hazard is a
tectonic event that has the
potential to cause a loss of
life or damage to property.
- According to UNISDR: 10+ people are
killed/ 100+ people are affected/state of
emergency is declared/international aid is
received.
- A tectonic event is a physical
occurrence that occurs as a
result of the movement of the
Earth.
- What are the threats from tectonic hazards?
- Earthquakes
- Ground outbursts
- Movement of the Earth's
crust has an impact on
buildings and infrastructure.
- Movement of the Earth's
crust has an impact on
buildings and infrastructure.
- Tsunamis
- Ocean waves with extremely long wave lengths
caused by earthquake tremors.
- Ocean waves with extremely long wave lengths
caused by earthquake tremors.
- Landslides
- Movement of masses of rock and debris
down a slope. Slope failure can occur as a
result of an earthquake or heavy rain.
- Movement of masses of rock and debris
down a slope. Slope failure can occur as a
result of an earthquake or heavy rain.
- Ground outbursts
- Volcanoes
- Lava flows
- This is the lava
expelled from a volcano.
- Lahars
- They are known as mud flows where
meltwater mixes with loose soil and ash.
- They are known as mud flows where
meltwater mixes with loose soil and ash.
- This is the lava
expelled from a volcano.
- Tephra
- Explosive blasts.
- Explosive blasts.
- Glacial outbursts
- Masses of water/ice is released from a
glacier and can be turned into a
mudflow.
- Masses of water/ice is released from a
glacier and can be turned into a
mudflow.
- Ash flows
- Ash flows also known as
pyroclastic flows.
- Ash flows also known as
pyroclastic flows.
- Ash falls
- Very disruptive.
- Very disruptive.
- Lava flows
- Earthquakes
- How are tectonic events measured?
- Mercalli scale
- This measures the intensity; it
quantifies the effects of earthquakes.
- This measures the intensity; it
quantifies the effects of earthquakes.
- Richter scale
- It is calculated from the amplitude of the largest seismic wave
during the event. It is a 10 logarithmic scale.
- It is calculated from the amplitude of the largest seismic wave
during the event. It is a 10 logarithmic scale.
- VEI
- Volcanic explosivity index
- Volcanic explosivity index
- Mercalli scale
- What are the causes of tectonic hazards?
- Asthenosphere is heated by radioactive
decay (of elements such as Uranium). As the
radioactive source is heating the
asthenosphere, the fluid magma circulates
because of the convection currents leading to
plate tectonics.
- Asthenosphere is heated by radioactive
decay (of elements such as Uranium). As the
radioactive source is heating the
asthenosphere, the fluid magma circulates
because of the convection currents leading to
plate tectonics.
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