1) Global hazards Flashcards
What are the four components of the earth?
Crust
Mantle
Outer Core
Inner Core
Characteristics of crust 3
Divided into tectonic plates
Around 20c
Between 8-65 km
What are the two types of tectonic plates?
Oceanic
Continental
Characteristics of oceanic plates
Thinner and denser
Characteristics of continental plates?
Thicker and less dense
Characteristics of mantle 2
Semi-molten rock
1200c
Characteristics of outer core 2
3700c
It is liquid
Characteristics of inner core 2
5500c
A solid ball of iron and nickel
What is a convection current?
When hot materials (molten rock) rise because they are less dense and cooler rock sinks because it is denser
How do convection currents move tectonic plates?
Magma near the outer core is heated
As it warms, it expands and becomes less dense
As it nears the crust, it begins to cool
The cooling magma becomes more dense and begins to sink
This motion creates circular convection currents in the mantle
These currents create friction with the crust above and cause it to move
What is a destructive plate boundary?
Two plates move towards each other
Where an oceanic plate and a continental plate meet, the denser oceanic plate is forced into the mantle and destroyed
This creates volcanoes and deep ocean trenches
Example of a destructive boundary
The pacific plate is being subducted under the Eurasian plate
What is a collision plate boundary?
Both plates are made from continental crust
They move towards each other
Both plates are forced upwards
This creates fold mountains
Example of collision plate boundary
The Eurasian and Indian plates are colliding to form the Himalayas
What is a constructive plate boundary?
Two plates move away from each other
Magma rises to fills the gap and cools to create new crust
Example of constructive plate boundary
The Eurasian and North American plates are moving apart at the Mid-Atlantic Ridge
What is a conservative plate boundary?
Two plates move sideways past each other or move in the same direction at different speeds
Crust isn’t created or destroyed
Example of conservative plate boundary
The Pacific and North American plate are moving past each other at the San Andreas fault
What is continental drift?
When convection currents move plates away from each other
What are hot spots?
Areas of intense volcanic activity that are away from plate boundaries
How was the chain of Hawaiin Islands made?
There is a hotspot in the crust
The hotspot remains stationary but the unusual heat causes the plats above it to move
How is a hotpot formed?
When a plume of hot magma form the mantle moves towards the surface, causing a flow of heat from the mantle to the crust
What is the volcanic cloud?
Gas steam and ash escaping from the volcano
What do the secondary vent and cone do?
Allow magma to escape from the sides of the volcano
Why do earthquakes occur at destructive boundaries?
Tension builds as one plate gets stuck as it subducts
Why do earthquakes occur at collision boundaries?
Tension builds as the plates are forced together
Why do earthquakes occur at constructive boundaries?
Tension builds along cracks within the plates as the plates move away from each other
Why do earthquakes occur at conservative boundaries?
Tension builds up when plates moving past eachother get stuck
How do earthquakes form?
Tension builds between plates
Convection currents build up, increasing potential energy
When potential energy is greater than friction, the plates eventually jerk past eachother, releasing the tension as shock waves
These seismic waves spread out from the focus
What is the focus of an earthquake?
The point in the earth where the quake starts
What is the epicentre?
The point on the earth’s surface above the focus
What are shallow focus earthquakes and where do they occur?
Caused by tectonic plates moving at or near the surface
They have a focus of between 0 and 70 km below the earth’s surface
What are deep focus earthquakes and where do they occur?
Caused by crust that has previously subducted into the mantle and are moving towards the core
Focus of 70 - 700 km below earth’s surface
Why are deep-focus earthquakes less damaging?
The shock waves have to travel through more rock to reach the surface so they lose much of their power
Another name for a transform plate boundary
Conservative
Another name for a convergent plate boundary
Destructive
Another name for a divergent plate boundary
Constructive
How do volcanoes form at destructive plate margins?
The oceanic plate is subducted
A pool of magma forms
It rises through vents in the crust
The magma erupts onto the surface
How do volcanoes form at constructive plate margins?
The magma rises up into the gap, forming a volcano
What are the two types of volcano?
Composite and shield
Characteristics of composite volcanoes
Tall and narrow
Violent explosions and lava bombs
Thick, sticky lava
Where do composite volcanoes occur?
Destructive plate boundaries
Example of composite volcano
Mount St Helens
Characteristics of shield volcanoes
Small and wide
Gentle eruptions, no lava bombs
Thin, runny lava
Where do shield volcanoes occur?
Hotspots or constructive plate boundaries
Example of shield volcano
Mauna Loa in Hawaii
What is bi-lateral aid?
Government to government
What is multilateral aid?
Co-ordinated response of many governments
What are NGOs?
Organisations such as Oxfam
3 ways of reducing the impact of tectonic hazards?
Building designs
Predicting and monitoring volcanoes
Early warning system for earthquakes
How can building designs reduce the impact of a tectonic hazard? 3
Buildings can be built from reinforced concrete or by using materials that absorb an earthquake’s energy
Existing buildings can be strengthened (e.g. cross bracing)
Pipelines can be designed to flex and not break
How can early warning systems help reduce the impact of a tectonic hazard? 3
People can start to prepare
Utilities can be shut off
People doing delicate jobs can stop, e.g. surgeons
How can predicting and monitoring volcanoes during eruptions reduce the impact of a tectonic hazard? 3
It gives people time to evacuate
Flights can be diverted from ash covered zones
Gas masks can be distributed early on
What is mitigation?
Reducing the impact of an earthquake
What is retrofitting?
The addition of new technology to older buildings
Examples of ways that buildings can be earthquake-proofed 3
Cross bracing
Automatic sprinkler system and gas shut off
Shock absorbers
How do tiltmeters work?
They measure the shape of volcanoes to detect bulges
How can measuring the soil/water pH help us predict earthquakes/eruptions?
May become more acidic before an eruption
What causes water and soil to become more acidic before an eruption?
An increase in sulfur levels
How can satellite imaging help us predict earthquakes/eruptions?
thermal imaging shows whether magma is rising
How can gas emissions help us predict eruptions?
Sulfur dioxide and carbon dioxide levels rise as magma rises
4 ways in which technology can be used to predict earthquakes
Tiltmeters
Measuring soil/water pH
Satellite imaging
Gas emisions
Which earthquake did we study?
The Nepal 2015 Earthquake - SEE CARDS
In which direction do winds move?
From areas of high pressure to areas of low pressure
What does hot, rising air do?
Create a belt of low pressure
What does cool, sinking air do?
Create a belt of high pressure
Why is the equator hot and wet?
The hot air causes a belt of low pressure, which creates rainfall
How do the three belts work?
The sun heats the earth at the equator, creating low pressure belt
The air cools and moves to 30 north and south of equator
Here, the cool air sinks, creating a high pressure belt with low rainfall
The cool air moves as surface winds either towards the poles or equator
At 60 north and south of the equator, the warmer surface winds meet cold air from the poles. The warm air rises, creating low pressure
Some air move towards the equator and the rest to the poles
At the poles, cool air sinks, creating high pressure.
This air is drawn back to the equator as surface winds
What are surface winds blowing towards the equator called?
Trade winds
Which direction do trade winds blow in the northern hemisphere?
From NE
Which direction do trade winds blow in the southern hemisphere?
From SE
Why do trade winds form clouds?
The two meet at the equator and are heated by the sun, making them rise and form clouds
What are surface winds blowing to the poles called?
Westerlies
Which direction do westerlies blow from in the southern hemisphere?
NW
Which direction do westerlies blow from in the northern hemisphere?
SW
What are the four types of climate?
Polar, dry, temperate, tropical
Characteristics of polar climate
Cold all year round
Characteristics of temperate climate
Moderate summers and winters
Characteristics of tropical climate
Hot and wet
Found near the equator - rising air from two cells meeting causes low pressure and lots of rainfall
Characteristics of dry climate
Low rainfall
Sinking air from two cells causes high pressure and low rainfall
What are winds like in pressure belts?
Weak
What are winds like between pressure belts?
Strong
How is extreme wind formed?
Wind moves from areas of high to low pressure
Winds are weak in high and low belts
Winds are strong between belts
When the difference between high and low pressure belts is large, winds can be very strong
How is extreme rain formed?
Precipitation is formed when warm air rises and cools, causing water vapour to condense
Air rises in low pressure belts. Rain is frequent and intense here
In high pressure belts, rainfall is low
The exact location of the pressure belts changes over time, so places like the UK can experience extreme rainfall
How is extreme temperature formed?
The equator receives most of the suns energy
The poles receive the least
Heat drives atmospheric circulation as warm air moves from the equator to the poles
Near the equator, the high pressure means there are few clouds to block the suns energy so it is often very hot
Hottest place on earth
Description of conditions
Explanation for conditions
Congo jungle
Over 30c the whole year
Sun rays strongest at equator/little cloud cover
Coldest place on earth
Description of conditions
Explanation for conditions
Antarctica
-50c in some areas
Albedo affect reflects heat/sun rays hit at angle
Windiest place on earth
Description of conditions
Explanation for conditions
Commonwealth Bay, Antarctica
Average speed of 80km/hr
Katabatic winds carry wind down from high ground
Place on earth that experiences most tornadoes
Description of conditions
Explanation for conditions
Tornado Alley
Over 500 tornadoes/year
Warm moist air from Mexico and dry cool air from Canada meet
Change in wind direction and increased speed creates spinning effect
Wettest place on earth
Description of conditions
Explanation for conditions
Cherrapunji, India
9300mm of rain in July 1861
Clouds forced to rise rapidly when meet Khasi Hills = relief rainfall
Driest place on earth
Description of conditions
Explanation for conditions
Atacama, Chile
15mm of rain on average
Rain shadow of Andes + cold ocean current = no moist air to form clouds
What are tropical storms?
Rapidly revolving storms characterised by low pressure
Names for tropical storms 3
Hurricanes, typhoons, cyclones
What is the Coriolis force and how does it work?
It causes the rotation of hurricanes
In the northern hemisphere, it deflects movement to the right
In the southern hemisphere, it deflects movement to the left
This means it sucks air in and creates an eye
What causes extreme winds in tropical storms?
An area of low pressure at the centre of the storm creates a big pressure difference to the surrounding area
What causes extreme rainfall in tropical storms?
Large amounts of warm, moist air are sucked in
The air rises and condenses, causing rain
Where do the majority of tropical storms take place?
Between 5 and 30 degrees north and south of equator
Mostly in northern hemisphere
How is a hurricane formed?
Sea temperatures reach 27c
The heat from the warm ocean is passed into the air by conduction.
This causes the warm air to rise, creating an area of low pressure
Wind moves from high to low pressure so is sucked in
The cloud gets hotter. The more moisture, the more heat
When winds reach 75 mph, it is a hurricane
As pressure drops and storm grow, it is affected by Coriolis force so it revolves and sucks in air from around it
An eye develops
When it reaches land, there is nothing to give it any energy so it slows down
At what wind speed will it be classed as a hurricane?
75 mph
Which typhoon do we study?
Typhoon Haiyan - SEE CARDS
What is it called when water and air currents weaken or reverse?
El Nino
What is it called when water and air currents get stronger?
La Nina
How often does La Nina occur?
Every 2-7 years
What are air currents normally like?
There is low pressure over the western Pacific where air rises. This is blown east
There is high pressure over the East around south america where air sinks, causing clear skies and dry weather
Trade winds blow to West , moving air back to the western side (Australia)
What does La Nina do?
It makes conditions more extreme
Trade winds are stronger and more cold water rises in the east
Characteristics of La Nina weather
Heavy rainfall and floods in the west - Australia
Droughts and less rainfall in the east - S. America
What does El Nino do?
Conditions are reversed
High pressure in west and low pressure in the east
Trade winds blow east
Winds high in atmosphere blow west
Characteristics of El Nino weather
Lower rainfall/ droughts in the west - Australia
Flooding to the east - S. America
What is a drought?
A period of time where rainfall is below average
Causes of drought 2
Changes in atmospheric circulation (Nina and Nino)
High pressure systems block the weather systems that cause rain
Distribution of Droughts
The areas most at risk include South Africa, Australia
Where to compare for extreme weather?
UK and Australia
Average summer temperature in Australia
33c
Average temperature in UK in summer
23c
Highest extreme temperature in Australia
51c
Highest extreme temperature in UK
38.5c
Lowest extreme temperature in Australia
-23c
Lowest extreme temperature in Uk
-27.2c
Worlds driest inhabited continent
Australia
Average rainfall in Australia
465 mm
Average rainfall in UK
1150 mm
Where has stronger extreme winds
Australia
Strongest wind recorded in Australia
400 km/h
Strongest wind recorded in UK
220 km/h
