The document discusses plate tectonics and associated hazards. It describes the structure of the Earth's interior with an inner core, outer core, mantle and crust. The crust is divided into plates that move via convection currents in the asthenosphere. Plates interact at boundaries that are either constructive, destructive, or conservative. Destructive boundaries result in volcanoes, earthquakes and fold mountains through processes like subduction. Plate movement is evidenced by magnetic striping in ocean crust. Hazards vary depending on the type of boundary and are managed differently in LEDCs and MEDCs.

1. HAZARDS
Combination of natural and human
processes. A hazard is an event with the
potential to damage human activity.

2. Structure of the Earth
• Inner Core
solid, iron and nickel
• Outer Core
molten, 5000 degrees
• Mantle
semi-solid, asthenosphere is upper mantle- 20km
thick
• Crust
divided into plates, combined with asthenosphere is
lithosphere, 80-90 km thick

3. Plates
• Plates are 7 large pieces of the lithosphere
• They float on asthenosphere and move through
convection currents
• Continental
30-70 km thick, light in colour (mainly
granite), composed of SIAL (silicon, aluminium), lighter
than oceanic, over 1500 million years old
• Oceanic
6-10 km thick, dark (mainly basalt), SIMA (silicon
magnesium), heavier than continental, younger than
continental (200 million years old)

4. Plate Tectonic Theory
• Alfred Wegener, German
• 1915
• Coastlines of South America and Africa- suggested continents were joined
together
• Originally one continent, Pangaea
• Split into 3 super continents which were later fragmented
• He could not prove why this happened, so theory was dismissed
• Sea floor spreading in Mid Atlantic Ridge brought his theory back to light
• Glacial deposits of similar ages in Brazil and West Africa
• Geologically corresponding mountains in US (Appalachian) and NW Europe
(incl. Scotland)
• Fossil remains of the Mesosauraus (270 million years extinct) found in South
Africa and Brazil
• Fossilised plants in India and Antarctica
• Palaeomagnetism shows periodically reversing magnetic fields (shown by sea
floor spreading)
• Earthquakes and Volcanic activity

5. Magnetic Striping
• Iron particles in solidified lava align with Earth’s
magnetic field
• Polarity
• Reversed regularly
• You can tell how old lava is by looking at its
polarity
• Palaeomagnetism
• Creates striped pattern
• Ocean crust spreading away from plate boundary

6. Destructive Boundaries
• Andean-type subduction
Oceanic beneath continental
Deep sea trench
Fold mountains
Deep focus Earthquakes
Steep-sided volcanoes
Nazca under South American plate – Andes Mountains, Peru-Chile trench, Nevado del Ruiz volcano
• Island Arcs
Oceanic and oceanic crusts
Steep-sided volcanoes formed
Shallow sea trench
Deep-focus earthquakes
South American under Caribbean plate formed Caribbean Islands, Soufriere Hills, Marianas Islands
• Continental collision boundaries
Two continental crusts colliding
Sediments between plates rise up to form fold mountains
Deep focus earthquakes
e.g. The Himalayas- Indo-Australian and Eurasian plates

7. Constructive Boundaries
• Ocean ridges
Sea floor spreading zones
Two areas of oceanic crust pulled apart
New ocean floor formed as lava fills gap
Shield volcanoes
Shallow focus earthquakes
e.g. Mid-Atlantic Ridge, Eurasian and North American plates
• Continental rifts
Rift valleys
Two areas of continental crust pulled apart
e.g. East African rift valley
Volcanoes are rare
Shallow focus earthquakes

8. Conservative Boundaries
• Plates sliding parallel to each other
• Friction and tension build
• Shallow focus earthquakes
• E.g. San Andreas Fault, California
• Pacific vs. North American plates
• Moving in same direction at different speeds
• Pacific is faster (5-9cm/year)
• Can cause transform faults

9. Hot Spots
• E.g. Hawaiian Islands
• Hot Spot within pacific plate
• Radioactive elements within mantle
• Magma rises to surface in plumes, forming small
shield volcanoes
• Hot spots are rooted, but the movement of the
pacific plate has caused Island Chains
• Only the volcano above the hot spot is active-
Mauna Loa
• Pacific plate is moving in a NW direction

10. Intrusive Volcanicity
• It’s what happens when the magma cools
before it reaches the surface
• Often exposed years later after erosion
• Batholiths are an example of a bubble of
solidified magma, often hundreds of
kilometres in diameter
• E.g. Dartmoor
• Dykes radiate from batholiths

11. Extrusive Volcanicity
• When magma reaches the surface
• Formation depends on type of lava
• Lava plateaux formed from fissure eruptions-
flat landscapes due to basic lava
• E.g. Antrim Plateau, NI
• Volcanic forms e.g. Volcanoes, Geysers and
Mud volcanoes

12. Volcanic shapes
• Shield- basic lava, short and wide
e.g. Mauna Loa, Hawaii
• Dome- viscous lava, tall and steep
e.g. Puy district, France
• Cinder cone
e.g. Paricutin, Mexico
• Composite cone- pyramid shape, layers of ash and lava
e.g. Mt Etna, Sicily
• Calderas- gas build up explodes and removes summit
Krakatoa, Indonesia

13. Volcanic Eruptions
• Icelandic
gently flowing basalt lava from a fissure
• Hawaiian
basalt lava flowing from a central vent
• Vesuvian
violent explosion after long inactivity
• Kratatoan
violent eruption destroying entire cone base leaving crater
• Pelean
violent eruption with pyroclastic flows
• Plinean
violent eruption where lava and pyroclastic materials ejected e.g. Lava bombs

14. Distribution of Volcanoes
• Mainly found along mid-ocean ridges
e.g. Mid-Atlantic ridge- Iceland
• Near subduction zones
e.g. ‘Ring of Fire’- Nazca plate under South American plate
• Along rift valleys
e.g. African rift valley- Mt Kenya and Mt Kilamanjaro
• Over hot spots
e.g. Pacific ocean- Hawaiian islands

16. Effects of Volcanic Activity
Primary
• Lava flow – threat to farmland and infrastructure
• Tephra – solid material of varying size ejected into the atmosphere
• Pyroclastic flows – hot, gas-charged, high velocity flows of gas and tephra, respiratory problems
• Volcanic gases – mainly carbon dioxide, killed 1700 people in 1986 at Lake Nyos, Cameroon
Secondary
• Lahars – volcanic mud flows, e.g. Nevado del Ruiz in 1985
• Flooding – melting of ice caps and glaciers e.g. Grimsvotn, Iceland 1996
• Tsunamis – giant sea waves e.g. Krakatoa, 1883 killing 30,000 in Sumatra
• Volcanic landslides
• Climatic change – volcanic debris in the atmosphere reduces global temperatures

17. Hazard Management- Prediction
• Swelling ground (rising magma)
• Seismic activity (splitting rock)
• Groundwater (gets hotter)
• Emission of gases (from crater)
• Magnetic fields (change)
• Animal behaviour

18. Hazard Management - Protection
• Monitoring the volcano (leaves time for evacuation)
• Risk assessments (identifying those at greatest risk)
• Land use planning (avoid building in high-risk areas)
• Controlling lava flows (trenches, walls, dynamite, pouring water on slow moving lava to set)
• Technical and financial aid (for LEDW)

19. LEDC Eruption -Montserrat
• Soufriere Hills, Montserrat, Caribbean
• Dormant for 400 years
• July 1995, started steaming and small ash explosions
• 1996, pyroclastic flows, southern population in danger,
most had fled
• 1997, residents move back to south as volcano went
through a quiet phase
• June 1997- exploded, large pyroclastic flows destroyed
settlements (Plymouth, capital city) and killed 19

20. Montserrat Aftermath
• British dependency, UK government had to provide:
• Evacuation of 7000 inhabitants to Antigua/UK
• Resettlement of population from south to north of the
island
• Constructing temporary shelters in north
• Re-establish air and sea links to Montserrat
• Building permanent housing
• Providing farming areas in north
• Moving the capital from Plymouth to Salem
• It cost the government £100million+ to minimise
effects and introduce a 3-yeaer development plan

21. MEDC Eruption- Mt Etna
• Northern Sicily
• 3310m tall and 460 miles long
• Lies on destructive Eurasian and African plate boundary
• Theories to its existence include hot spot over European plate and
fractures in lithospheric slab
• Densely populated lower slopes due to banana, fig and pistachio
farming
• Skiing, cafe and cable car bring tourism
• Erupted in may 2008
• Lava travelled 6km
• 200 earthquakes
• Flank eruption (lava exposed on eastern side as opposed to crater)
• Artificial channels dug and water cooling used to divert lava from
villages

22. Etna Aftermath
• Activity continued for 6 months
• No deaths
• Sulphur dioxide found 3000 miles away
• Temporary closure of airport
• Dip in tourism
• Dip in economy (farmland ruined)

23. Benefits of Volcanoes
• Geothermal power - Iceland use this to heat greenhouses and
this enables it to be self-sufficient in most food stuffs
• Volcanic soils – lava weathers to produce fertile soils rich in
minerals. Farmers work at the low lopes of volcanoes such as Mt Etna,
Sicily
• Volcanic rocks – they make good building materials also pumice
• Tourism – tourists are able to climb to the crater of mount Vesuvius

24. Earthquakes
• An earthquake is oscillation of the earth’s crust
• Measured on a Richter scale (logarithmic)
• May also be measured on the Mercalli scale
• Triggered mostly by plate boundaries moving but also
by movement in fault lines, volcanic activity and
human activity (e.g. Drilling)
• Epicentre happens underground
• Focus is where it impacts on the surface
• Surface waves- Raleigh and Love
• Body waves- primary and secondary
• Easier to say ‘where’ than ‘when’

25. MEDC Earthquake
• Northridge, LA, 1994
• 6.7 on the Richter scale
• San Andreas fault line
• Focus was 18.4km deep
• 0430 am
• 57 deaths
• 1500+ injuries
• 11 main road closures
• 11,000 landslides triggered
• 20,000 homeless
• Many homes without gas, electricity and water
• 6,000 aftershocks
• $30billion worth of damage

26. LEDC Earthquake
• Gujarat, NW India, Jan 2001
• Epicentre was Bhuj
• Collision boundary- Indian and Asian plates
• Intraplate earthquake (didn’t happen on boundary)
• Focus was 17km deep
• 7.9 in Richter scale
• 30,000 deaths
• 160,000 injuries
• 1 million homeless (90% homes destroyed)
• 800,000 buildings damaged
• All 4 hospitals were destroyed
• Heritage was destroyed e.g. Forts, palaces, temples
• Communications disrupted (power lines down)
• Looting
• 80% water and food supplies damaged
• Widespread diarrhoea and gastroenteritis
• $5.5 billion in damages

27. Tsunami
• A tsunami is a large ocean wave which is
caused by sudden motion on the ocean floor
• This is usually caused by an earthquake
• Pacific ocean accounts for 80% tsunamis
• Oceanic under continental plate

28. Boxing Day Tsunami
• 26th December 2004
• 9.0+ on Richter scale
• Sumatra, Indonesia
• India plate under Burma plate
• 275,000 deaths
• Affected 10 countries
• Aceh was worst-affected
• Aid was slow to reach the region
• Minimal secondary deaths
• School uniforms for children
• 60% of fishermen back to work 1 year on, catching 70% of previous years’ capacity
• The war-torn region now sees less violence from the opposing sides since the
tsunami
• 100,000 houses pledged, one year on and only 20,000 are finished
• Restoration of livelihood and water/sanitation were the focus of spending
• Indonesia was granted one third of the total aid contribution

29. Multi hazard urban environment
MANY HAZARDS HAVE INTERRELATIONSHIPS
• Los Angeles
Earthquakes- lies on fault line
River flooding- increased interception as well as heavy winter storms
Coastal flooding- heavy winter storms cause waves to pound coast
Drought- high evapotranspiration and little rainfall
Wildfires- hot summers dry vegetation, and wind spreads fires more easily
Landslides/mudslides- fires remove vegetation, loosening ground
Smog- due to intense car use
Crime- highest in USA
• Mexico City
Earthquakes- Cocos plate subducted under North American plate (last earthquake in 1985, 8.1 on Richter)
Smog- worst air quality in the world, old cars running in a small area
Sinking ground- sediments in old lake bed on which the city lies are contracting
Crime- increased by 80% in the 90’s, few crimes are solved
Reasons for Mexico City linked to unconstrained growth, meaning many poorly-built structures are erected,
only to easily fall down in an earthquake/landslide. 40% of people live in informal settlements there.

30. Additional Clarification
• 31: Oceanic Ridges
• 32: Sea floor spreading
• 33: Destructive boundaries (OC)
• 34: Destructive boundaries (OO)
• 35: Destructive boundaries (CC)
• 36: Fold mountains

31. Oceanic Ridges
• E.g. Mid Atlantic Ridge
• 1000km wide
• Result of sea-floor spreading
• 10-15mm/year
• Shallow-focus earthquakes due to transform
faults which cause sideways slipping
• Volcanic activity occurs
• Forms submarine volcanoes (sometimes rise
above sea-level, shield shape)

32. Sea Floor Spreading
• Constructive plate margins
• Space between diverging plates
• Filled with basaltic lava
• New crust continually being formed
• Youngest part of Earth
• Form mid oceanic ridges and rift valleys
• E.g. Jordan- East Africa 5500km

33. Destructive plate margins
oceanic-continental
• Oceanic plate goes under continental (heavier)
• Subduction
• Ocean trench
• Fold mountains
• Oceanic plate melts in Benioff zone
• Magma oozes up through plate and forms volcanoes
(andesitic lava)
• Island arc may occur here
• Triggers earthquakes
• e.g. Nazca vs. South American plates
• Andes, Peru-Chile trench, Cotopaxi volcano and Ecuador
earthquake of 1906 were formed this way

34. Destructive plate margins
oceanic-oceanic
• Ocean trenches
• Subduction
• Submarine volcanoes
• Island arc
• Earthquakes
• E.g. Pacific vs. Philippine plate
• Marianas trench, Island of Guam formed

35. Destructive plate margins
continental-continental
• Little subduction due to low density
• Fold mountains as two masses push upwards
• Shallow focus earthquakes may be triggered
• E.g. Indo-Australian vs. Eurasian plate
• Sediments from the Sea of Tethys rose to form
Himalayas
• India at risk of earthquakes, e.g. Gujarat, 2001

36. Fold Mountains
• Formed by Destructive plate margins (but not
ocean-ocean)
• Have anticline and synclines (folded rocks)
• Volcanic areas (e.g. Andes)
• Huge areas of overfolds
• Uplifted central areas e.g. Altiplano, Andes
• Earthquakes
• Highly weathered and eroded features e.g.
valleys, gorges, glaciers