volcanoes (not completed)

Question 1

oceanic-oceanic plate divergence

Answer 1

• two oceanic plates diverge, fractures are formed at plate boundary
• magma rises from mantle at the zone of divergence to form sea floor -> sea floor spreading, lava flows out onto sea floor, cools and solidifies
• more magma piles up and solidifies, forming a chain of mountains on sides of mid oceanic ridge
• as plates contnue movng apart, mountains move away from the mid oceanic ridge and new mountains are formed -> youngest nearest, oldest furthest
• magma buids up and solidifies to form undersea volcanoes along mid-oceanic ridge -> when they grow above sea level, they are volcanic islands
• mid-atlantic ridge was formed when north american plate and eurasian plate moved away from each other

Question 2

continental-continental plate divergence

Answer 2

• when continental plates diverge, tensional forces result in fractures at boundary -> faulting
• when sections of crust extend along fault lines, tensional forces cause central block of landto subside btwn a pair of parallel faults, forming rift valley
• volcanoes and earthquakes are found along the rift valley
• tensional forces also causes land masses surrounding a block of land to subside -> form balck moutain between parrallel faults
• nubian boundary of african plate moves away from the somalian boundary of african plate, forming east african rift valley

Question 3

rift valleys and block mountains

Answer 3

• at divergent plate boundaries
• tensional forces from plates being pulled apart causes parts of crust to be fractured -> faulting
• rift valley -> east african rift valley bc mvt of somalian boundary of african plate from nubian boundary of african plate
• block mt -> back forest ingermany caused by mvt of eurasian plate and north american plate

Question 4

earthquakes

Answer 4

• vibration in earth crust caused by the sudden release of stored energy in rocks along faukt lines
• plate mvt causes the slow build up of stress on the rocks found on either sides of fault
• when rocks cannot withstand the increasing stress, they can slip many metres
• point of sudden emergy release -> focus
• point on eart surface above focus -> epicentre
• stress from ground results in many smaller earthquakes > aftershocks

Question 5

factors affecting extent of earthquake damage

Answer 5

1. population density
   - sparsely populated areas, affect fewer ppl
   - city, more casualties and damage
2. level of preparedness
   - amount of preparation taken by authorities and citizens make a difference on impact
   - e.g. having evacuation plans, trained rescue workers
3. distance from epicentre
   - closer to epi, dmg more severe
   - christchurch, new zealand, 2011, epi a few km away from city centre, city suffered frm more damage than other cities
4. time of occurrence
   - where ppl?, what ppl doing?, how prepared ppl are? -> chances of survival
   - sleeping ppl -> trapped, more deaths
   - more than 2400 ppl did, after midnight, sun moon lake region in taiwan, 1999
5. type of soil
   - sediments loose and unconsolidated, seismic waves amplified, ground becomes unstable and saturated soil flows like liquid, structures affected by liquidefaction, greater damage
   - christchurch, 2011, new zealand, many structures abandoned bc of liquefaction

Question 6

hazards associated with earthquakes
1. tsunamis

Answer 6

• formed by 1) mvt of sea floor during large EQ at subduction zones, 2) explosive underwater volcanic eruption e.g. anak krakatoa indonesia, 3) landslide above sea level that causes materials to plunge into water
• seismic waves by offshore EQ forces out a mass of seawater -> when reaching shallower water -> greater friction slows down water -> water increases in height
• 2004, EQ magnitidue 9.2, indian ocean, tsunami, damage in coastal communities inn12 countries

Question 7

hazards associated with earthquakes
2. disruptions of services

Answer 7

• disrupt supply of electricity, gas, water, affecting large area
• vibrations on ground snaps pipes and breaks cables , outbreak of fires
• communication services like TV and telephone connections affected
• EQ in Kobe, Japan, 1995, disrupted services to abt a million of its residents

Question 8

hazards associated with earthquakes
3. landslides

Answer 8

• shakign of ground, weaken slopes of hills and mountains, soil, rock, vegetation debris move down from slope
• mudflows due to heavy rain saturating the soil, causes soil debris to move down slope
• 1970, EQ off the coast of Peru, landslide, rapid rate, flattened town Ranranhirca within seconds, killing most residents

Question 9

hjazard associated with EQ
4. destruction of property

Answer 9

• widespread destruction to many homes
• tohoku, japan, 2011, tsunmi 10km inland, strcutural dmg resulted in many ppl being displaced from homes, severe housing shortage, concerns about long term consequences on health of ppl

Question 10

hazards associated with EQ
5. destruction of infrastructure

Answer 10

• EQ cause cracks in infrastructre, roads, bridges
• transportation disrupted bc unsafe
• EQ Kobe, Japan, 1995, places of cities became inaccesible

Question 11

hazards associated with EQ
6. loss of lives

Answer 11

• due to collapsed buildings during EQ/tsunamis

Question 12

risks of living near volcanoes

Answer 12

1. massive destructions by volcanic material
   - pyroclasts and lava have high temo, burning area
   - low silica lava moves rapidly over long distances, dmg to larger area
   - inhaling hot ash, srs injury or death
   - volcanic bombs, srs dmg to property (Kilauea in hawaii, sibce 1983, destroy many homesand highways)
   - landslides due to structural collpase of volcanic cone during eruption, obstruct river flow, floods, block roads, bury village and farmlands (town of armero, lahar killed many
2. -pollution
   - ash particles ejected can disrupt human activities over long distances from volcano
   - thick plumes of ash settle on ground, block sunlight, suffocate crops, severe respiratory issuesfor ppl and animals
   = releases carbon dioxide, sulfur dioxide , carbon monoxide and hydorgen, harmfyl to ppl and envt
   - Iceland, 2012, extensive volcnic ash clouds, danger to aircraft, airspace closure over europe, delays to flights, loss of money to airline industry

Question 13

benefits of living near volcanic area

Answer 13

1. fertile soil
   - lava and ash breka down to form fertile volcanic soils, rich in kinerals
   - volcanic soils in java and indonesia support growth of tea, coffee and rice, supporting large rural population
2. tourism
   - volcanic acivities offer many tourist activities
   - hiking and camping
   - rich in history
   - pompeii, italy, ruins buried by ash frm mt vesuvius, unearthed site revealed buildings, ottery, mosaics left intact
3. precious stones and minerals
   - volcanic rocks rich in precious stones and minerals , diamonds, extracted after million of years
   - when refined, they become seful industrial tools and jewellery
4. geothermal energy
   - derived from heat of earth crust
   - when ground water comes into contact with hot rocks, it heats up and eruots as hot water, harnessed to drive turbines to produce electricty
   - most electricity in Iceland is geothermally produced

Question 14

short term responses to EQ (occur immediately, lasting for 2 wks)

Answer 14

1. search and rescue
   - locating and freeing people trapped under collapsed buildings quickly
   - +ve: some survivors trapped without food for a few weeks were found
   - -ve: rescue workers, limiyted time of 72 hrs to locate trapped survivors

+ve example: 2011 EQ tohoku, japan, sniffer dogs, heat sensors, rscued many successfully
-ve example: 2011, EQ tohoku, japan, rescue workers limited time of 3 days, finding survivors in 2 affected town areas

2. emergency, food, medical supplies
   - medical treatment for injured survivors
   - clean drinking water for survivors, prevent dehydration and spread of diseases
   +ve: provision of immediate aid, allowing survivors to carry on with lives
   -ve: insufficient medical supplies, food, water, to large numbers of affected people, social unrest

+ve: 2002 EQ in Afyon, Turkey, immediate response from Trukish Red Crescent society, delivered 20000 tents, 50000 blankets, 3000 heaters
-ve: 2010 EQ in Haiti, looting and fighting among survivors for food and medical supplies

Question 15

long term responses to EQ

Answer 15

1. rebuilding of infrastructure
   - improving of infrastructure after EQ
   - +ve: authorities develop strict buidling codes, ensure infrastructure restored at a higher safety level than before
   - -ve: reinforced building built to resist EQ maynot be protected against tsunamis, need addtional protection like breakwaters

+ve example: 1995, Kobe, Japan, spent billions developing technology, more EQ resistent buildings
-ve example: Chile 2010, EQ resistent building ssuffered from extensive dmg caused by tsunami

2. provision of healthcare
   - provision of health options, long term counselling, loss of loved obes, homes, jobs, long lasting trauma
   +ve: identify problems and address them early
   -ve: improving heathcare options like storing resilience of ppl is very challenging, many survivorsafter 2010 haiti EQ still lack access to basic neccessities

+ve: a year after 2010 christchurch EQ in new zealand, probelsm of anxiety and depression in all age groups of affected population, many heakth workers deployed to the area

Question 16

responses to EQ preparedness measures
1. land use regulation

Answer 16

• a set of rules implemented to restrict developments in certain areas
• e.g. california, usa, all new building developments are built across fault lines or areas at risk of liquiefaction.
• land use regulation restricts construction of new buildings on low lying land prone to tsunamis. developemtn is only allowed when prtective barriers like seawalls are built
• e.g. along coasts of japan where pacific ring of fire is located
• +ve: reduces dmg, fewer buildings and people at risk
• -ve: regulations are implemnted in areas that are already privately ownded or built up, private owners are reluctant to move bc they believe another hazard will not occur
• -ve: costly if authorities buy the land from private owner

Question 17

responses to EQ preparedness measures
2. infrastructure

Answer 17

• develope with advanced engineering to withstand vbrations by EQ
• effective buildings designs prevent the collapse of buildings and minimise damage
• roads and bridges and dams can be built to withstand EQ so they do not collapse easily, will be easily repaired when damaged
• homes, office, factories can be fitted with trip switches to prevent fires from breaking out
• e.g. Taipei 101, taiwan, fitted with steel and reinforced concrete, damping devices, as shock absorbers and counterweights that move in opposite direction of motion of EQ + wide and heavy bases taht decrease the chances of building collapsing and withstand the EQ better
• +ve: building design leads to fewer lives lost, faster rescue, evacuations, les money spent on recovery
• -ve: construction and maintennace of these buildings are costly

Question 18

responses to EQ preparedness measures
3. emergency drills

Answer 18

• ppl practise the steps to take when EQ occurs, creating awareness among the population and reduces the level of panic and irrational behaviour
• ppl take part in drills by moving to safe locations, listening to instructions of trained personnel and practising first aid
• they may also become members of local response teams that assist ppl
• japan conducts emergency drils on 1 Sept to commemorate Disaster Prevention Day where EQ ofhigh magnitude is stimulated. main roads are blocked to create possible road conditions in an event of an EQ. emergency vehicles hv to seek alternative routes to reach affected areas
• -ve: based on most srs EQ expereibced in past e.g. Tohoku japan occured in a scale never expereinced before in Japan, so drills were insufficient
• -ve: insufificint time for evacuation as EQ are diffiult to predict

Question 19

responses to EQ preparedness measures
4. earthquake monitoring and warning systems

Answer 19

• by studyin the histiry of when and where EQ have occured, it provides an estimation of frequency and magnitude of EQ at particular faukt lines, predcitiing the occurence of EQ
• seismic risk maps show the likelihood of locations at risk from earth movements or liquefactions
• -ve: infromation is not precise about time, location, magnitude of future EQ
• +ve: installing EQ sensors in EQ prone zones helps to monitor frequency of vibrations and detect possible developments of EQ. EQ motion data is gathered from hundreds of observation stations installed on bridges and roads in japan. the stations monitor ground motion, predict occurrence of an EQ
• -ve: EQ sensors are expensive to get, install and use. warnings o not provide sufficient time for evacuation. noise, lightning or device failure may interfere with seismograoh, false warnings. its difficult to also give accurate warnings when mutiple EQ occur close to each other

Question 20

responses to EQ preparedness measures
5. tsunamis monitoring and warning systems

Answer 20

• tsunami monitoring stations are found in various tsunami prone places in the world. generally near plate boundaries
• linked to warning systems which are activated to warn ppl about the occurrence of a tsunami
• network of pressure sensors, seismograohs, deep ocean tsunami detectors located in Hawaii, USA to monitor and forecast the path of tsunamis
• surface buoy is connected to pressure sensor acnchored to seafloor. temperature and pressure are measured and relayed to the buoy every 15 secs. information is sent via satellite to land-based tsunami warning stations for analysis
• +ve: when warnings are sent, early evacuation saves lives
• -ve: prone to giving false warnings when waves are high. little time to evacuate once tsunami approach

Question 21

continental continental plate convergence

Answer 21

• collide and push against each other
• both plates are too thick and buoyant -> no subduction
• plates break and slide along fractures in crust
• layers of rocks in the upper part of crust are compressed tgt
• compressional forces creates immense pressure -> layers of rocks to buckle and fold -> folding
• layers may fold upwards or sideways -> fold mts
• earthquake triggered by plate convergence

e.g. Nepal EQ in 2015
e.g. himalayas -> indian pate and eurasian plate converged

Question 22

oceanic oceanic plate convergence

Answer 22

• denser plate subducts under the less dense one
• sibduction zone
• a long narrow depression in sea floor -> oceanic trench formed at zone of subduction
• the subducted oceanic plate causes the mantle material above it to melt, forming magma
• magma rises throguh fractures to form volcanoes -> formig a chain of islands
• friction produced during the subduction process -> earthquakes

e.g. mariana islands -> a chain of volcanic isaldns
e.g. pacific plate and philippine plate -> mariana trench and mariana islands

Question 23

oceanic continental plate convergence

Answer 23

• denser oceanic plate subducts under lighter continental plate
• long narrow deep oceanic trench formed at pt of subduction
• at subduction zone, subducted oceanic plate causes mantle matrial above it to melt -> magma
• magma rises the ES throguh fratures -> volcanoes and volcanic eruptions
• EQ may occur on continental plate
• oceanic australian plate and continental eurasian plate -> sunda trench and fold mt barisan mt
• oceanic nazca plate and continental south american plate -> peru-chile trench and fold mt andes mt in south america

Question 24

transform plate boundaries

Answer 24

• slides slide past e/o -> transformation fault
• friction between moving plates -> stress to build up along plate boundaries -> energy stored up in crust
• rocks cannot contain the ressure -> energy released -> radiate shock waves throguh crust and ES
• large faults occur as rocs break up and move in a series of sudden jerks -> EQ
• pacific plate and NA plate -> san andreas fault
• north anatolian fault -> eurasian plate and anatolian plate