Plate Tectonics Flashcards

Question

Inner core

Answer 1

Ni, Fe Over 5000 degrees Solid

Answer 2

Radioactive decay generates heat Lower parts of asthenosphere heat up > less dense so rise Move to top > cool, dense and sink Circular movement = convection current Creates drag on the base of the tectonic plates, causing them to move

Answer 3

Diverging Mantle is under pressure from plates above - pressure released when plates move apart Causes mantle to melt > magma > less dense than plate so rises > volcano Plats don't move uniformly, causing build up of pressure > cracks = fault lines > earthquakes Mid-ocean ridges Rift valleys

Answer 4

Oceanic-oceanic constructive margin | Under water volcanoes erupt, cool and new crust is formed which can build up to above sea level eg Iceland

Answer 5

Continental-continental constructive margin Rising magma under land causes continental crust to bulge and fracture > fault lines Crust between parallel faults drop eg East African Rift System Volcanoes also found eg Mt Kilimanjaro

Answer 6

Converging Oceanic-Continental > deep sea trench, fold mountains as well as volcanoes (oceanic crust heated by friction and contract with upper mantle > magma rises) and earthquakes (plates get stuck > build up of pressure and jerk past each other) Continental-Continental > deep sea trench, island arcs as well as earthquakes and volcanic eruptions

Answer 7

``` Destructive continental- oceanic More dense oceanic crust forced under continental = subducted Up to 10km Also at continental-continental More dense plate subducted ```

Answer 8

Clusters to volcanic islands that occur in a curved line eg Mariana Islands > very gradual > sea mounts form and break surface in a line parallel to plate boundary (50-100km away)

Answer 9

Destructive continental-continental Neither subducted = no volcanoes Pressure can build = earthquake Fold mountains can form eg Himalayas

Answer 10

Form where plates meet > made of sediments accumulated on continental crust > folded upwards along edge of continental crust

Answer 11

Plates move past each other Become locked together > pressure builds Plates jerk = fault lines = earthquake eg Pacific/N American plate San Andreas Plate

Answer 12

Volcanic activity away from plate margin Magma plume - vertical column of magma that rises up from the mantle. Volcanoes form above magma plumes. Magma plume remains stationary, but crust moves above it Volcanic activity that was above hot spot decreases as it moves away New volcanoes form in new part of the crust Chain of volcanoes forms eg Hawaii (proven by turn of islands = change in crust movement)

Answer 13

Tephra - solid material ejected into the atmosphere Pyroclastic flows - very hot, gas charged, high velocity flows made up of gases and tephra Lava flows Volcanic gases

Answer 14

Lahars - volcanic mud flows Flooding - melting of glaciers and ice caps Tsunamis Volcanic landslides Climatic change - volcanic debris can reduce global temps

Answer 15

``` Beneath earth's surface High pressure = semi-molten mantle Pressure releases = molten magma Less dense than rock so rises up Forced to surface through cracks and solidifies ```

Answer 16

If hot springs mix with surface deposits Very fine grained soil Brightly coloured - minerals

Answer 17

Destructive margin Steep sides due to high viscosity of lava - short distances and convex Composite cone = andesitic lava and layers of ash and lava

Answer 18

Constructive margin/hotspots | Gentle slope - low viscosity of lava - flows long distances

Answer 19

Constructive margin Fairly flat surface due to low viscosity Layers of lava and long linear vent Lava plateaux

Answer 20

``` Gas emissions Ground deformation Thermal monitoring Satellite images Remote sensing Mass movements and failures (landslides) Seismometers > seismographs ```

Answer 21

Catania, Sicily, Italy MEDC > GDP = $35926 per capita 3323m Constructed over an old shield volcano > stratovolcano Truncated by several small calderas eg Valle del Bove 5-10km horse-shoe shaped caldera/depression open to earth (collapsed during eruption > landslide) Persistent eruptions with minor lava emissions from one of 3 prominent summit craters Not regarded as particularly dangerous - fertile volcanic soils

Answer 22

End of 1991, lava began to pour from vents high on eastern flank in Valle del Bove and advanced on settlement of Zafferana 1. Large earth barrier 10m high and over 40m long which held back lava for several months 2. Spring 1992 lava spilt over barrier towards Zafferana. Smaller barrier built and were overwhelmed by advancing lava, destroying orchards and a few small buildings 3. Dropping concrete blocks by helicopter blocked the primary feeder channel - dropped through roof of upper lava tube 4. May 1992 engineers blasted openings in the lava tube to encourage a new direction of flow. This stopped lava advancing on Zafferana and eruption ended 10 months later in 1993

Answer 23

Low effusion rates during eruption Would lava ever have reached Zafferana? High elevation of eruptive vents - 2200-2350m - well away from inhabited areas. Would have had to flow 8km more to become a serious threat Large possibility of diverting flow into uninhabited areas - at least 7km from nearest village However it is not always possible to stop lava flows on Mount Etna eg 2002 a more serious eruption destroyed the ski station of Piano Provenzana and part of another station at Rifugio Sapienza, clouds of ash rained down on the area, particularly affecting the city of Cantania

Answer 24

Philippines > generally LEDC > GDP = $2765 per capita 1991-1993 Destructive margin - oceanic crust moves towards and is subducted by continental Eurasian plate Oceanic plate > magma > volcano Mt. Pinatubo not erupted since 1380 - not considered a hazard by locals who work on fertile soils

Answer 25

1. June 1991 first signs of eruption 2. Thousands evacuated from Angeles and 15000 from Clark American air base 3. 12 June explosion > steam and ash 30km up > 3rd largest eruption in the century 4. 50cm ash fell nearby and over 10cm within 600km 5. Followed by earthquakes and torrential rain (combined with ash > thick mud) 6. Destroyed all crops and caused buildings to collapse > 200000 including local hospitals and factories 7. Power supplies cut off for 3 weeks and water supply contaminated 8. Roads and bridges destroyed

Answer 26

Ash ruined 1991 harvest and 1992 planting was impossible Over 1 million farm animals died - lack of grass Farmers refuge in large cities > shelter and foods in shanty-town style refugee camps > disease spread rapidly 1993 typhoons - heavy rainfall and lahars (mud flows) 700 deaths - only 6 as a direct result of eruption - others from disease and suffocation in lahars Some did not return top former homes - everything planted is destroyed Others decided to return as mountains were still their home Shanty refugee camps deemed safer than returning to an area where eruptions, earthquakes and lahars still occurred until the regrowth of vegetation stabilised the slopes after many years

Answer 27

Built up tension at boundary > pressure released when plates jerk past each other, sending out seismic waves from the focus in the lithosphere/crust Shallower focus causes greatest damage as epicentre is closer to focus Human activity may cayse eg large reservoirs puts pressyre on surface rocks Also reactivation of old fault lines eg 23/09/02 Dudley UK 4.8

Answer 28

Travel through earth's interior, radiate from focus line ripples on water

Answer 29

1. Richter scale - amplitude of seismic waves, logarithmic, energy release proportional to magnitude 2. Mercalli scale - intensity of event and impact, 12 point scale, 1=2 on Richter - detected but hardly felt, 12=8.5 on Richter - total destruction

Answer 30

Ground shaking (initial), soil liquefaction - shaken soils with high water content lose mechanical strength and behave as a liquid, landslides/avalanches, collapsing buildings, destruction of road systems and service provisions eg gas, fries from ruptured gas pipes etc, flooding, disease, food shortages, disruption to local economy

Answer 31

``` Earthquake magnitude and focus depth Location and boundary Bedrock Population density Buildings and structural vulnerability Level of development Earthquake preparedness ```

Answer 32

Giant sea waves generated by shallow-focus underwater earthquakes, volcanic eruptions, underwater debris slides and large landslides into the sea Long wavelengths in open ocean with low wave heights > 700kmph On reaching shallower water bordering land, they rapidly increase in height Drawdown - wave trough infront causing a reduction in sea level Can be over 25m high (number of waves)

Answer 33

Wash structures inland and backwash takes back out Water and debris cause drowning and injury Effects felt 500-600m inland Most at convergent (subduction) boundaries, 90% within Pacific basin

Answer 34

``` Height of waves and distance travelled Length of event causing tsunami Extent to which warnings can be given Coastal physical geog - offshore and incoastal area Coastal land use and population density ```

Answer 35

12 Jan 2010 4:53pm LEDC > GDP = $820 per capita 7 Richter scale 13km depth Seismically active area > complex plate margins surrounding > 1 destructive and 2 conservative Enriquillo-Plantain Garden Fault System locked for over 250 years

Answer 36

Energy released along 65km of fault Land-movement 1.8km By Jan 24, 52 aftershocks of over 4.5 Richter scale Epicentre 25km SW capital in Leogane Killed 230000 (8.8 Chilean 1 month later killed only 800 due to clear disaster response plan) Destroyed 60% capital Port-au-Prince - 70% buildings collapsed, 86% in slums, only 50% access to latrine, 2`% leftover buildings needed demolishing 4000 amputees, 1.5m homeless, 4000 prisoners escapes, $8bn damage and losses

Answer 37

Dominican republic > water, food, heavy machinery for rescue, hospital use Iceland emergency team in 24 hours No emergency plan - lack of awareness of what to do Lack of co-ordination > 100 UN personnel, many health workers and 1/4 civil servants killed Priority initially given to security troops not aid Money was spent on aid workers' accommodation and transport Few NGOs spoke French Some projects not addressed 1500 camps in Port-as-Prince had only 1 delivery of water per week - untreated water drunk > October 2010 first case of cholera > endemic due to lack of expertise, medical staff, clean drinking water or disposal of human waste 6900 deaths and 500000 cases reported Rape and sexual attacks not uncommon in camps due to lost husbands, tents easy to break into, little privacy at washing facilities and latrines, badly lit at night and no policing Unretrived corpses decay in mass graves Little communication > roads and elec damaged Aid ships turned away from devastated port

Answer 38

2004 tropical storm Jeanne killed 3000 In a hurricane belt > 2008 hurricanes killed 800, 60% harvested destroyed and many landslides - not yet recovered > services from NGOs and UN > destroyed 700000 homes Unstable gov Poor - 2008 32% GDP from family abroad, 70% on less that $2 a day, 1% Haitians control half wealth, limited developed infrastructure and health services Poor planning, governance and shortage of health nurses and underfunded health system > 25 doctors and 11 nurses per 100000 - urban Population 9.8 million - high incidence of AIDS/HIV (2.2% aged 15-49) > highest outside sub-Saharan Africa LE 60 IM 86/1000 - malnourishment

Answer 39

World Bank cancelled half debt and gave 5 years before repayments should begin - also gave food for 200000 6-23 months, funding for 140000 schools within camps, new water supply system in 6 rural locations > encourage to stay there, work with locals to rebuild homes in a hazard resilient way Cash for work programmes allowed some Haitians to support themselves - 20% jobs lost and 85% agricultural, workers - destroyed July 2010, 98% rubble remained uncleared and 1.6million in camps Jan 11 relief appeal at over £1bn - 72% of what is required - 810000 in camps, 95% children in earthquake zone returned to school Need for a long-term strategy - many traumatised, amputees no jobs, some nurses work elsewhere for better pay

Answer 40

17 Jan 1994 4.30am, federal holiday Los Angeles, USA MEDC > GDP = $53042 per capita 6.7 on Richter scale, focus 18.4km Result of movement along a previously unknown thrust fault - ground acceleration Highest ever instrumentally recorded in a North American EQ

Answer 41

57 died - federal holiday and early morning so most in homes Over 1500 seriously injured 12500 buildings moderate - serious damage ]11 major roads seriously damaged and closed for rebuilding Other roads damaged up to 32km from epicentre More than 11000 landslides - block roads and damaged water lines Landslide damaged homes - Pacific Palisades area Over 20000 immediately homeless 11 hospitals suffered some structural damaged and unable to serve 600 recorded aftershocks - 5.6 11 hours after, weakening already damaged buildings 80km south, score board collapses onto seating at Anaheim stadium Several days after, 9000 premises without electricity, 20000 without gas, 48500 little/no water Over $30 billion damage and over 700000 applications to federal and state programmes for financial assistance

Answer 42

Demonstrated that some buildings do not perform well eg multi-storey wood-frames building and those with a weak first floor (due to parking on ground floor) New building must conform to building codes eg reinforced schools and hospitals New law: by 2005, hospitals must have earthquake-proof acute care units and emergency units

Plate Tectonics Flashcards

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