Geography Restless Earth

• The Earth formed approximately 4.5 billion years ago
• The Earth is made up of four concentric layers:
  • Inner Core – This is in the centre of the earth = hottest. It is solid = Iron and Nickel with temperatures of up to 5,500oc.
  • Outer Core – This is a liquid layer= Iron and Nickel and is extremely hot with temperatures like the inner core.
  • Mantle – This is the widest section of the Earth = 2,900km + semi-molten rock called magma. Towards the top of the mantle the rock is hard, but lower down nearer to the centre of the earth the rock is soft and beginning to melt.
  • Crust – This is the thin outer layer of the earth = 0-60km + solid. 2 Types:
    • Continental - Carries Land
    • Oceanic - Carries Water

• Tectonics vary in size
  • Major plates include the Pacific, Eurasian, African, Antarctic, North American and South America, and the Indo-Australian.Plates = different materials + 2 types:
• Continental crust = thicker, older and lighter. 35 km thick on average + less dense than oceanic crust. More complex than oceanic crust in its structure + origin and is formed primarily at subduction zones at destructive plate margins
• Oceanic crust is younger and heavier + it is mainly formed at constructive margins or spreading mid ocean ridge

Destructive:

• Where two plates collide and one plate flows beneath the other – subduction.

  • Earthquakes + volcanoes occur,

  • e.g. Nazca Plate and South American Plate

• An oceanic plate (denser) is pushed towards a continental plate (less dense) by convection currents. The oceanic plate is subducted the continental plate (subduction zone), = deep ocean trench. It is the Oceanic crust which sinks down into the mantle (heavier). As it descends friction, increasing pressure + heat from the mantle melt the plate. Some of this molten material can work its way up through the continental crust through fissures +cracks in the crust to collect in magma chambers + causing volcanoes. The movement of the plates grinding past one another can create earthquakes, when one plate eventually slips past the other releasing seismic energy. As the plates push together, continental crust is squashed together + forced upwards (called folding).

Collision:

• Two continental plates collide and the two plates buckle

  • Many earthquakes occur here

  • E.g.: Indo-Australian and Eurasian plates

• At these margins 2 plates of similar density are forced toward each other. Neither plate descends into the mantle bcos similar density. 2 plates crumple into one another + fold upwards into fold mountains. At these margins we get fold mountains and earthquake activity, + a fantastic example of this is the Himalayan mountains.  

Conservative:

• Two plates slide past each other

• Earthquakes occur 

• E.g.: San Andreas Fault, California = Pacific plate is moving NW at a faster rate than the North American plate.

• At conservative margins mountains 2 plates either slide past each other in opposite directions, or 2 plates slide past each other at different speeds = stress energy builds as the plates snag and grind on one another sending sends shock waves through the earth’s crust = Earthquakes

Constructive:

• Constructive - Rising convection currents pull crust apart forming volcanic ridge - Mid-Atlantic Ridge

  • E.g.: Eurasian and North American Plates

  • Both earthquakes and volcanoes (movement of magma)

• At these type of plate margins two plates are moving apart leaving cracks and fissures, lines of weakness, that allows magma from the mantle to escapes from the highly pressurised interior of the planet.

• This magma fills the gap and eventually erupts onto the surface and cools as new land.  this can create huge ridges of undersea mountains and volcanoes

• Sea islands are created.

Ocean Trenches 

• Deep water areas that run along a coastline which has a destructive plate margin.
• Created by subduction + mark the point where the Oceanic crust is being pushed under the Oceanic crust.
• Often quite a large section of continental crust between this margin + the ocean's edge, + sometimes a volcanic island arc an be found in between the trench and the continental shelf.
• Not to be confused with mid ocean ridges, (long ridges of mountains created by 2 plates moving apart at a constructive plate margin). Where these mountains rise above the level of the sea Islands such as Iceland are formed.

Fold Mountains:

• Large mountain ranges where the layers of rock within them have been crumpled as they have been forced together.  
• They can be formed at destructive or collisional plate boundaries, where tectonic plates are moving together forcing layers of rock to be crumpled upwards.  
• The layers of rock can  form 2 basic features:
  • Up = Anticline
  • Down = Syncline
  • Over the top of themselves = Overfold

Where: Europe, France/Italy border

Formation: 30 million years ago by a collision between African and Eurasian plate

Farming:

• On the sunnier, warmer side of slopes.and therefore uses transhumance (seasonal movement of animals). In Summer- cattle taken to high Alps to graze allowing crops to grow on valley floor. In the winter- return to valley floor in cattle sheds.

• Change over years:

  • Cable cars used to transport milk to dairy's

  • Farmers buy additional food so can remain on valley floor all year

Tourism:

• 100 million tourists visit each year

• In the winter tourists visit for skiing, snowboarding and ice climbing.

• In the summer tourists visit for walking, mountain biking, climbing.

• New villages have been built to cater for tourists.

• Worry is that winters are warming up so there is less snow:

  • more people skiing on worn slopes

  • damages vegetation and the surface below

  • increases number of bare slopes and risk of soil erosion

Hydro-Electric Power (HEP):

• Steep slopes, high precipitation and summer melting of glaciers makes fast flowing rivers which are ideal for generating HEP.

• Valleys are narrow

  • Easier to dam and there are lots of lakes to store water

• Some cheap HEP is used by industries which require high input of electricity.

Mining- salt, iron ore, gold, silver and coper are mined

Problems:

Relief: high and steep

• mountain valleys=narrow and gorge like.

• little flat land for forming settlements.

Climate: increasing height becomes colder, windier, wetter and more snow

• short growing season.

• oftenimpossible to grow cropsat such high levels.

soils- stoney, thin and infertile 

Accessibility: roads and railways= expensive and difficult to build

A volcano is a cone shaped mountain formed by surface eruptions from a magma chamber inside the earth and is found at destructive and constructive plate margins

A volcano produces-

• Lava

• Ash

• Cinders

• Pumice

• Gas

• Steam

• Pyroclastic flower (super-heated ash and steam)

How Volcanoes Are Formed:

• Magma escapes through a crack in the earths crust (called a vent)

• Lava and other products are thrown out from the circular hole at the top called the crater.

• Each time an eruption takes place, a new layer of lava is added to the surface of the volcano.

• Laval accumulates at the top of the crater to form the cone shape.

Terms:

• Crater = bowl shaped depression formed at the summit of a volcano when gases are ejected

• Vent = pipes/openings in volcano through which magma passes

• Subsidiary cone (aka secondary or parasitic) = a new cone can be formed on a side of a volcano when the main vent is blocked

• Pyroclastic flows = dense,destructive mass of very hot ash and lava fragments along with gases ejected explosively from a volcano and normally flows at a high speed

Types of Lava:

• Acid Lava -

  • has a high silica content

  • because it’s so vicious (thick) it only travels short distances before cooling

  • gases do not escape easily

• Basic Lava -

  • low silica content

  • runny so will flow long distances before cooling

  • gases do escape easily

  • It’s other name is basalt

Composite volcanoes-

• Lava is usually thick and flows slowly however is hardens quickly, forming a steep sided volcano

• Tall cone with narrow base and made up of ash and lava in alternate layers

• Irregular with violent explosions

• Subsidiary cones and vents form

Shield Volcano-

• Lava is runny and flows quickly and spreads over a wide area forming a low, flat volcano, made only of lava

• Frequent non violent eruptions

Primary effects:

• The immediate impact of the volcano eruption e..g loss of life,homes,animals and crops

Secondary effects:

• Effects triggered by the eruption e.g. earthquakes can cause:

  • local damage. tsunamis, lahars (mud flows). alterations in river courses, effects on climate, nutrients added to the soil as lava and ash breaks down, loss of trade. need to rebuild and stress for people

Advantages:

• Fertile soil when the lava weathers

• Tourist attraction, e..g trips to the rim of a crater, hotel accommodation

• Minerals, e.g. sulphur, borax, pumice

• Lava flows build new land eg. Hawaii and Iceland

• Hot springs for bathing and heating

• Heat used to generate electricity

Disadvantages:

• Explosions and eruptions leading to:

  • Dangerous gases

  • Loss of lives, homes, animals and crops

  • Diseases and fires

  • Avalanches, mudflows and floods

  • Loss of wildlife

Monitoring and Predictions of Volcanic Eruptions:

• Heat and gas emission - detects changes in the magma beneath a volcano as it rises before an eruption

• Laser reflectors - tilt meters record actual movement in the Earth’s crust

• Global positioning satellites (GPS) - be used to sense minute changes in the position of land near a fault line of volcano

• Seismometers - measure how and when the ground shakes. These patterns can help predict earthquakes may indicate that a volcano eruption is likely

Iceland:

Iceland lives on the Mid Atlantic Ridge, a constructive plate margin separating the Eurasian plate from the North American Plate. As the plates move apart magma rises to the surface to form several active volcanoes located in a belt running roughly South West - North East through the centre of Iceland.

• Hot spring water is carried by pipe to Reykjavik (capital), giving people cheap and reliable energy which does not damage the environment. Most of the water used is from Borehole 45km (over 300 degrees celsius in heat)

• Electricity is generated from geothermal resources of hot water (underground in many parts of iceland). This steam is used to power turbines for houses/factories

• Tourism - The Blue lagoon is a geothermal heated lake used for bathing and skin cleansing (the minerals in the water). It is popular with tourists. The Strokkur Geyser is also viewed with tourists as a fantastic sight to see.

Primary Effects:

• March 2010 - magma broke through the crust, start of 2 months of dramatic/powerful eruptions that would affect people all around the globe. Eruptions mainly lava.

• April 2010 - Over a period of several days in mid April violent eruptions belched huge quantities of ash. This is because the lava came out underneath a glacier and was super-cooled immediately, fractures turned into grains (ash) when it solidified.

• When the ash fell, it coated many agricultural lands with thick layers of ash, halting some products from being made

Secondary Effects:

• Flooding - As the eruption occurred underneath the glacier a huge amount of melt water was produced. Vast torrents of water flowed out from underneath the ice

• The closure of European Air Spaces affected many people including business people and tourists. Industrial production was affected as the raw material could not be flown in and products could not be exported out. People as far away as Kenya were affected, having products not being exported meant people were fired/had their salaries cut.

• Local water supplies were contaminated with fluoride.

• Homes, roads and services were damaged and disrupted.

Posotive:

• Tourists which were stuck on holiday had to stay at their accommodation because it would be unsafe to fly home

• Lava and ash in nutrients making the soils in volcanic areas very fertile and good for agricultural use

• The rocks from the eruption can be used for building

• The valuable source of geothermal energy just below the surface is now easy to access. This can be used to produce electricity and provide hot water for industrial process, heating swimming pools and even melting snow on pavements

• Small quantities of gold, copper, silver, lead and zinc are often found in volcanic regions. Deposits of sulphur can be mined from volcanic regions.craters and used to bleach sugars, make matches and fertilisers.

Negative:

• Volcanoes producing ash can go up in the air and damage airplane parts. Therefore during eruptions, airports will be forced to close.

• Flooding caused by the volcanoes can damage roads forcing cars to not use roads as transport until fixed

• The ash can be stop production of agricultural goods, this is because ash will coat fields very thickly and kill plants/animals

• Industry can be shut down because they cannot transport their goods out to sell and they can't import raw resources

• The cost for repair can be millions/billions - this depends on the build and location

Immediate Responses:

• Ash falling close to the ground forces people to be evacuated from their farms and villages

Key Information:

• On the Mid-Atlantic Ridge which formed a Stratovolcano with a caldera

• Relatively small

• Is a fissure + explosive eruptions

• Mixing on lava types (rhyolitic and basaltic)

• Ash clouds were transported by jet streams

• Flooding caused by melting glaciers

A supervolcano is a volcano that is much bigger than a normal volcano. They do not form a cone shape, they form a large depression called a caldera. Emits atleast 1000km3 of magma.

How:

• Magma rises through cracks in the crust forming a large magma chamber below the surface.

• The pressure of the magma causes a circular bulge on the surface.

• The bulge cracks, creating vents for lava to escape through.

• Lava erupts out of vents causing earthquakes and sending up ash and rock.

• As the magma basin empties, the bulge is no longer supported so collapses

• When the eruption finishes there is a big crater (caldera) left where the bulge collapsed.

Comparing Volcanoes and Supervolcanoes

• Cone Shaped | Caldera
• Eruptions = Frequent | Not frequent
• Locational Scale | Global Scale
• Small in Area | Massive Area of actual volume 80 km in width
• Ejected 10km cubed | 100 km cubed

About:

• Scale of the caldera in Yellowstone is 85 km by 45 km wide

• The Yellowstone Supervolcano is next due to erupt every 600,000 years, however this one has not erupted yet and we are 640,000 years at the moment and therefore overdue

Short Term:

• Before eruption large earthquakes + ground swell up + earthquake would unleash pressure
• 50 km in atomosphrye magma
• Killed by :flowing ash, lava flows + sheer explosives (Within minutes tens of thousand would be dead) whilst coating Iowa + Gulf of Mexico + would cover USA with 5 inches of ash
• Loudest thing since last one

Long Term:

• Block out sun with ash = nuclear winter -> Extinction world level event
• Plant life would nearly be destroyed

What are they?

Vibrations in the earths crust which shake the ground surface.

Why do they happen?

Friction. When plates try to move they are held still by friction. This can be with another plate or with the mantle. The forces pushing the plate keep pushing until there is so much force that it overcomes friction and the plate suddenly jerks forwards.

Focus = Where the plate moves underground, where the earthquake originates.
Epicentre = The point on the surface straight above the focus.
Shockwaves = Radiate out in all directions which get less powerful the further away from the epicentre.

Measuring Earthquakes:

• Seismology - the study of the Earth’s movements

• Seismometers - pieces of equipment, buried in the Earth’s surface to find movement

• Seismographs - the results from the seismometers, recorded on paper with a moving needle

Earthquake Waves:

• 1st waves in an earthquake will shake the ground UP then Down in a longitudinal movement. = P / PRIMARY waves  They travel fastest, and can also cause back and forth movement.

  • Relatively weak and cause the surface to move in a back and forth motion.  

• Next waves to arrive are S / Secondary waves, which travel slower through the crust.  

  • These waves cause the crust to move from side to side at right angles to the outward motion of the main wave.  

  • They are also called TRANSVERSE waves and are known to cause the most damage.

The Richter Scale:

• Measures magnitude (energy released) of an earthquake.

• Measured using a seismograph.

• It's logarithmic- means that an earthquake with magnitude of 5 is 10 times more powerful than one with a magnitude of 4.

• Most people don't feel earthquakes of magnitude 1-2.

• Major earthquakes are above 5.

 The Mercalli Scale

• Used to indicate intensity/effects of an earthquake

• Effects are measured by asking eye witnesses of what happened, and takes into account effects on Earth's surface, people and buildings.

• Given a number between 1-12, sometimes Roman numerals:
  • I (1)- Rarely felt by humans.
  • II-IV (2-4)- Moderate effects- felt by people indoors.
  • V-VII (5-7)- Strong effects, causing panic felt by everyone, structural damage.
  • VIII (8)- Destructive to poorly built structures, only slight damage to those well designed.
  • IX-XII (9-12)- Disastrous, total destruction.

Earthquake Effects: 

Earthquakes can destroy settlements and kill many people. Aftershocks can cause even more damage to an area. It is possible to classify the impacts of an earthquake, by taking the following factors into account:

Social Impacts:

• Short Term - People killed / injured, homes destroyed, communcation and transportation disrupted, water pipes burst
• Long Term - Diseases may spread, rehoused (sometimes in refugee camps)

Economic impacts:

• Short term - Shops and business may be destroyed. Looting may take place. The damage to transport and communication links can make trade difficult.
• The cost of rebuilding a settlement is high. Investment in the area may be focused only on repairing the damage caused by the earthquake. Income could be lost.

Environmental Impacts:

• Short Term - The built landscape may be destroyed. Fires can spread due to gas pipe explosions. Fires can damage areasof woodland. Landslides may occur. Tsunamis may cause flooding in coastal areas.
• Long Term - Important natural and human landmarks may be lost.

Prediction:

• Long Term - General predictions can be made by looking at the earthquake history of an area to work out the probability of an earthquake and therefore to plot a hazard shaking map
• Short Term - The Japanese and Americans have invested heavily in computer technology to constantly monitor seismic activity. The world wide network of seismometers helps with this and also picks up foreshocks. In Japan their seismometers pick up P Waves before damaging S Waves, sending notifications to people's phones

• Dilatancy Theory - When a rock is stressed due to plate movement it can dilate which means the rock expands. This is caused by micro-cracks + fractures in the rock opening up and becoming larger. This only seems to start when a rock is roughly halfway towards its breaking point

  • We can check this by checking the rocks electrical resistance changes and also the uplift of water

• Animal behavior - Animals change their behavior patterns before an earthquake. For example snakes come out their hibernation in Winter and freezing to death, two months later a major earthquake hits the area. This is because animals are sensitive to sound, temp, touch, light intensity and magnetic fields.

• Problems - Unlikely that general predictions will ever be more accurate than within a year or two, perhaps ten, this would lead to high amounts of stress and the development of an area plummeting down before an earthquake.

Preparing

• Evacuation plans + Medical and emergency plans + Education - “Drop, cover, hold”

Protection

• Training people may involve holding earthquake drills and educating people via TV or radio.

• Emergency kits and store them in their homes.

• Earthquake-proof buildings have been constructed in many major cities e.g. a building which is safe from a 8.0 magnitude earthquake is in Istanbul's International Airport where the whole building lifts of the ground which helps dampen and slow down the movement of the building.

• Automatic shutters on windows +counterbalances +cross bracing the corners of buildings +build buildings out of strong concrete and steel frameworks

LEDC - India:

• use shake tables to test building materials

• use rubble from the 2001 quake used to build foundations

• the reinforced steel and concrete pillars in foundation

• walls made out of hollow concrete bricks

• reinforced roofs - less likely to collapse

• bridges designed to withstand earthquakes

Causes:

6.3 magnitude earthquake struck New Zealand at 12:51 on 22 February 2011.  The epicentre 6 miles Southeast of Christchurch + the focus was very shallow at 3.1 miles.  The earthquake was on a conservative plate margin where the Pacific Plate slid past the Australian Plate in the opposite direction.  Technically an aftershock from a larger earthquake in 2010 but the impacts were more severe.

 Primary (caused directly by the earthquake)

• 181 people were killed and around 2,000 people were injured
• Hundreds of kilometres of water and sewage pipes were damaged
• 50% + of Central City buildings severely damaged including the city’s cathedral which lost its spire
• Liquefaction caused lots of damage to roads and buildings
• Part (size of 20 football fields) of the country’s longest glacier was broken off creating a large iceberg
• 80% of the city was without electricity

Secondary (result from primary effects)

• Business were put out of action for long periods causing losses of income and jobs
• Schools had to share classrooms because of the damage to other school buildings
• Damage to roads through liquefaction made it difficult for people and emergency services to move around
• People were affected mentally by the earthquakes and needed support
• Christchurch could no longer host Rugby World Cup matches so lost the benefits, e.g. tourism and income, they would bring

Development:

• GDP per capita (average income) = $27,700 per person each year
• People living in poverty = N/A
• Life expectancy = 81 years old
• People per doctor = 2.4 doctors per 1,000 people
• Adult literacy rate = 99% over 15 years old can read/write
• Access to clean water = 100% of people have access to clean water

Short Term

• Cared for the most vulnerable people and ensured people were safe from dangerous buildings
• Chemical toilets were provided for 30,000 residents
• Areas were zoned (green, orange, white, red) to classify damage/cost of repairs
• International aid was provided in the form of money (around $6-7 million) and aid workers
• Strict building code limiting disaster
• Full emergency management structure in place within 2 hours. 
• Fire services coordinated search and rescue 
• New Zealand Defence Force, providing logistics, equipment, transport, air-bridges, evacuations, supply and equipment shipments
• Temporary banks

Long Term:

• Paid $898 million in building claims
• Provided temporary housing and ensured all damaged housing was kept water tight
• Water and sewerage was restored for all residents by August
• Roads and houses were cleared of silt from liquefaction by August and 80% of roads/50% of footpaths were repaired
• Rebuilding completed in 2016
• Pushing ‘Drop, Cover, Hold’
• Rezoned city - no rebuilding on land affected by liquefaction 

About:

Caused by the North American Plate sliding past the Caribbean Plate at a conservative plate margin.  Both plates move in the same direction, but one moves faster than the other.  The pressure that was built up because of the friction between the 2 plates was eventually released causing a magnitude 7 earthquake on the Richter Scale with an epicentre 16 miles West of Port-au-Prince + a shallow focus of 5 miles.  The earthquake struck at 16:53 on Tuesday 12 January 2010.

Primary (caused directly by the earthquake):

• 316,000 people were killed and 1 million people were made homeless. 3 million people were affected by the earthquake
• 250,000 homes and 30,000 other buildings, including the President’s Palace and 60% of government buildings, were either destroyed or badly damaged
• Transport and communication links were also badly damaged by the earthquake
• Hospitals (50+) and schools (1,300+) were badly damaged, as was the airport’s control tower + the main prison was destroyed and 4,000 inmates escaped

Secondary (result from primary effects):

• 1 in 5 people lost their jobs because so many buildings were destroyed.  Haiti’s largest industry, clothing was one of the worst affected
• The large number of deaths meant that hospitals and morgues became full and bodies then had to be piled up on the streets
• The large number of bodies meant that diseases, especially cholera, became a serious problem
• It was difficult getting aid into the area because of issues at the airport and generally poor management of the situation
• People were squashed into shanty towns or onto the streets because their homes had been destroyed leading to poor sanitation and health, and looting became a real problem

Short Term:

• $100 million in aid given by the USA and $330 million by the European Union
• 810,000 people placed in aid camps
• 115,000 tents and 1,000,000+ tarpaulin shelters provided
• Healthcare supplies provided to limit disease
• Lack of immediate aid through poor planning, management and access meant that people had to try and rescue each other
• 4.3 million people provided with food rations in the weeks following the earthquake

Long Term:

• 98% of the rubble on the roads hadn’t been cleared restricting aid access
• 1 million people still without houses after 1 year so still have to live in aid camps
• Support for people without jobs, which equates to nearly 70% of the population, through cash/food-for-work projects
• Temporary schools created and new teachers trainee
• Water and sanitation eventually supplied for 1.7 million people

Compare

• Both on conservative margin with a similar magnitude and epicentre near major city
• Christchurch - 6.3 + Haiti - 7
• Lots of aftershocks
• Liquefaction
• Major public buildings destroyed e..g Cathedrals in both
• Similar times of year (Jan/Feb)

Contrast

• Christchurch - 185 deaths, Haiti - 230k deaths
• Extent of damage/numbers of buildings destroyed over 250k in Haiti
• 300k injured in Haiti
• Speeds of recovery:
  • Christchurch; 1-2 years  + Haiti - 20-30 years
• Haiti relied on foreign aid
• Christchurch relied on money from government. 

A tsunami is a special type of wave where the entire depth of the ocean is set in motion by an event - often an earthquake - which displaces the water above it and creates a huge wave.

Where: Indonesian island of Sumatra in Asia.

When: 2004

Earthquake richter scale: 8.9

How: Pressure from the indo-australian plate pushing under the eurasian plate.

Short term effects:

• Buildings destroyed + Flash floods. + High waves. + Initial earthquake.

Long term effects:

• Homeless. + Dead/missing people. + 5,000 houses destroyed.

Short term responses:

• Blankets and aid flown in.

• Water provided.

• Tents.

• Bulldozers cleared dead bodies to prevent disease.

Long term responses:

• Rebuilding.

• International tsunami warning put in place.

• £100 million donation.