Plate Tectonics lesson notes

I wrote these at AS, I don't know whether more detail is required at A2. Presumably not.

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  • Created on: 16-12-16 16:34
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Carmen Gaywood SJF
Global Distribution of Tectonic Hazards
Tectonic Hazards
Earthquakes and volcanoes can be hazardous if they are affecting people or economy. This often happens in
developed countries with high population.
Primary Hazard Earthquake Volcano
Secondary Hazard Tsunami Volcanic bombs
Ground displacement Ash
Ground movement (waves) Lava
Soil liquefaction Pyroclastic flows
Some tectonics are more hazardous than others, due to:
- Frequency
- Capacity to cope (HIC/LIC)
- Economy level
- Population level
- Magnitude
- Aerial extent (how big the area affected is)
- Weather hazards
Intra-plate earthquakes. These occur in the middle or interior of tectonic plates and are much rarer than boundary
earthquakes. They happen due to old faults shifting ­ rocks are still settling in from billions of years ago (old tectonic
Hotspot Volcanos are fed by underlying mantle plumes that are unusually hot compared with the surrounding
mantle. They are found in the middle of tectonic plates. A volcanic hot spot is an area in the mantle from which heat
rises from deep in the earth.
Densely packed earthquakes on map subduction of plates
Thin linear movement of plates
High energy volcanoes occur at convergent plate boundaries eg near the pacific plate.
Low energy is divergent
Oceanic Fracture Zone (OCF)
Belt of tectonic activity under the ocean.
Continental Fracture Zone
Belts of tectonic activity on mountain ranges. From Spain via the Alps to the Middle East to the Himalayas.
Tsunami Hazards
There's escalation in terms of damage and loss of life as tsunamis are a series of waves caused by seabed
People lose their lives as they return home inbetween waves, thinking it was over. They can rarely be over
an hour apart.

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Carmen Gaywood SJF
Not a hazard out to sea because they're low in height (300mm ish)
Factors Influencing the strength of a Tsunami
1. Duration
2. Wave amplitude, water column displacement and distance travelled
3. Physical geography of the coast ­ water depth and gradient at the shoreline
4. Degree of coastal ecosystem buffer eg protection by mangroves and coral reefs
5. Timing of the event and therefore quality of early warning systems
6. Degree of coastal development and its proximity from the coast.…read more

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Rocks are magnetised so they face north ­ this can be used to tell how old they are.
Paleomagnetism: The zone of magma `locking in' or `striking' the earths magnetic polarity when it cools. Molten rock
aligns itself to the magnetic north. Scientists can use this tool to determine historic periods of large
scale tectonic activity through the moving of plates. It creates a geo timeline.
Benioff zone
Area of seismicity corresponding with the slab being thrust downwards in a subduction zone.…read more

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Carmen Gaywood SJF
Range of Impacts from Volcanoes
Local Regional International
Domes Lahars/floods Tsunami
Lateral Blast Health effects of gases Pyroclastic fall
Earthquakes/ Ground Inflation Pyroclastic flows Volcanic Gases
Structural Collapse/ debris avalanche
Pyroclastic Flows
A mixture of gas and hot rock. Contains glass shards, pumice, crystals and ash. Can be up to 1000C. Most hazardous
when it comes out sideways.
Volcanic Gases
Poisonous. Normally includes water vapour, sulphur dioxide, hydrogen and carbon monoxide. It can accumulate in
valleys and kill people. Colourless and odourless.…read more

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- Waves stretch areas apart so water falls ­ buildings above fall into spaces that were occupied by water before.
Long term damages Cost of repair
Short term damages Delivery of aid (roads broken etc)
Disaster Risk Equation (used for all disasters)
Things affecting the Risk Equation
Unpredictability. People may be caught out by either the timing or magnitude of an event.
Lack of alternatives. Economic reasons (can't move elsewhere)
Lack of knowledge skills
They work there (can't move elsewhere)
Dynamic hazards.…read more

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Resilience after = Cleanup. Speed to get it back to how it was before.
Disaster Risk and Age Index
1. Increasing world risk of hazards.
2. Ageing population.
The young and old can't respond to natural disasters because they don't have economic power.
PAR Model (Pressure and Release)
1) Explain why earthquakes and volcanoes have predictable, similar and yet different distributions.
An earthquake is the release of pressure after two plates have slid against eachother.…read more

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More duration of pressure building = more magnitude
An earthquake where pressure is released in one go is 1 jolt ­ less damaging.
More jolts (duration) = more damaging
Aerial extent
The larger the area affected, the greater the impact.…read more

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The Impact of Low Development Levels
1. Economic components
- Low Incomes
- Low spending power
- Poor quality of life
- Lack of savings to fall back on
- Lack of insurance
2. Social components
- Poor health
- Poor nutrition
- Low levels of education
- Low life expectancy
- Poor housing ­ low sanitation
- No kind of generational inheritance, whether it is
wealth, knowledge or education.…read more

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Economic costs associated with both hazards and disasters of all types have increased significantly since
1940. people claim on insurance more rather than fixing something themselves like in the past.
As we become more globalized we are more affected by things eg disaster in China means there could be no exports.
Number of events hasn't changed but we are more exposed.
Climate: The average weather conditions over 40 years.…read more

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Volcanoes happen along convergent and divergent plate boundaries.
How a volcanologist knows a volcano is going to erupt
Shallow, earth tremors caused by the surface of the crust when magma comes out.
Bulging on the volcano (magma is rising)
Gases will come out of the volcano ­ white smoke and a sulfur smell.
Water vapour heated from rising magma so steam rises.…read more


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