structer of the earth


the structure of the earth

the earht is know to about  4.6bn year old, this is know form radiomeitce dating.  This oldest rock are found in the Percambrian shields  of Canda and africa. 

layer of earth in order outside in 

oceanic crust.  

continetial  crust 

mantle(soild  with semi plastice  upper layer anthosmee) 

inner core 


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layer and dicotiunites

crust is soild 

mantle  semo liquid uper portion (250km) otherwise soild.)

inner core liquid

outcore soild. 

layer are seroarted  by bouridiase called  discontituttes. it serpate layer witin  the earth by commsion and state. 

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evidence for structer of the earht.

crust is the most accebsey layer of the earth thus makeing  it the most stuide layer of the earth.   howevery evdidne is still need for the  state, densiy and compostion  of the core and mantle can be studey by 2 methode. 

direct observaton 

  • xenolith. are old rock  encased in yougen rock. 
  • ophilites. are fregament of ocean crust  obudted on to conetila margin at subduction zoen.
  • deep  miing drliing activty. reval what at butom of the crust. deep mine up 3km deep 

indrrect obvsratio 

  • seismolgy. stae density and infer comstioi of inner part of earht.  earth quake proudce 3 type of wave.  P S L wave.  
  • meteroies.  ramims  of plants which have been desrtoyed collsion on inplosion. 
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seimloly is the study  of earthquake.  an earthquake is a varbation  in the earht crus cuased by  realse  of friction along a flaut plain (frauctienr in crust)  that have built  up betwen two plates. 

epcie center. point direclty abvoe  the focu of the earht quake. 

focuus  orign of the earthqukae with the curs (0-700KM) 

the depth of earth quake  recored are shalow (0-70km)  intermeida(70-300km)  or deep( 300-700km) 

earthquake travle in 3 wave type which are P S L 


S= secondary wave 

l=long wave 

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recording earth quake

recoder  on a insrtument know as seimonter and the trace it give is called  sesimogram. a seismgram  recorde the trace of all wave  durring an earth quake. 

what a seismometer look like  (

what a seismgram look like  (

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measring earthquake

the richter and mercial scale are the most widely used scales. 

the richter scale 

  • musaer  streght of earthquake 
  • lormtiache scale 
  • grade 1-9 


  • muasert inster of the earthquake 
  • less sifacface than ricter 
  • based on obseration 
  • damged caused varriers  depdein on disstase  comistion ,of bedrock  state of  the subsurface.  
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earthquake hazard

damge to stuster 

  • building meartials 
  • age of bulding 
  • type of building 

ground  moovment 

  • crack may open 
  • mudslides or landslide 
  • liqefaction unsoclated rock contian a lot of   weater and during and earthquake  thought make groudn act like quick sand 


  • japensn word menaing "wall of weater"
  • triged by under  sea earht quake , movemtn at ocean ternc or submaire landslide. 
  • reach speed of 700km per hour 
  • reach hight of 30 meter high.
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social and enocmice of earthquake

short term effect. 

  • copplased bulding 
  • damged infaruate 
  • broken gas pips 
  • healry care unable to cope 

long term effect 

  • cost inclduin stricter  codes
  • redlvopment of the infastrution 
  • couting interal aid

socla effec 

  • homless 
  • unemployment 
  • loss of family meber 
  • diesses 
  • shortgae of food 

econimce effect 

  • loss of revune 
  • loss of skilled ad unskiled workers 
  • cost of rebuildin 
  • cost of redevloment 
  • cost of earthquake  predtcion nd mointior equiment 
  • depdecy on froigein aid. 
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earth quake engerinerring

numebr of mehtode  incudign  buoidng regltion  can reudce the inpact of earthquake  on the built envrioment. brick is a common builidng  matetyl but is easily damged. the flowing way can make it more earht quake proff. 

  • icorp woodn frame or steal roods
  • reseting hight of the building 
  • usign storne mortar 
  • usienf light wight martilse for  the roof. 

in urban area within deloped couitre there offen high poolation density and high rise structer. in earthquake  pron area enginger. 

  • ofen reocmde buildig have interlinked  steel frame rate.  
  • favour  bulidng that beihive or pradhe shape 
  • ensure brideg and montaway ar refroied essse dodl  tried struecer thes will have ston foundatio. 
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earthquaek loaction

are confied to the palte bondaries were to plate  bounarises were 2 plate meet.  these are know as sekice area of the crust.  the interplate  area know as aseimic as they are  not prone to earthquake activty. 

map showing earthquake  (

  • larges earht quake happn at dissctitue plate boruabese
  • earhtquake shalow  couitee plate boruadry 
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earthquake predction

earth are unpredcatlae..   some couireise  vast sums of moyne  of atepimign  to predction of erh quake.   it is is inspslbr to predction  aout time loaciton and magtiue of a earht quake. 

if they are pedto worgen they   can cuasw alerm  which cause trafrice cauase, paicne buyin in shoops.  in a fasel alamre poolation many not react in the same way again when it is the real thinik 

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plate tectonics

map showign the earth plaes  (

major plates 

  • pafice plate 
  • nazca 
  • north america plate 
  • south america plate 
  • eurasism 
  • africa plate 
  • indo austrailte plate 
  • arabie plate 
  • antractic plate 
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construtive plate boundaries

at a constiuvete plate 

  • covertion current in plate  pull plate  apart
  • a gap is crust it created  gernater shalow focue earthquake 
  • hot magma rise  thought  the gap  form astheommoe to the surface 
  • new crsut is formed

feauter at contricty plate boruadry 

spreading rate  ocena ridges varys form  2cm yr  in the alacitce  to 9cm/yr  in the pafice. 

map showing tech plate boundaries  (

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contiennetal drift

is the theroy  that the earht  plates  have drifted  to their present  day potion over  million if year  anc coitue ti move. 

contrubtion to theory  of plate tectoinse. 

covecvton current

parialty  moltnen and this proivdeed the lubraction  neaceasry  for  plate  movment. this driivng  machises   world for plate movnent.  covcetion  current  criaulrte  the upper  mantle.   this then rise the  ocean ridges soeaed then coll forming desutie plate bouradyr.

contiolen fit . costline of the usa  euore and south america and  africa  with few overlaps. 

sturtcal  feauter. 


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destrucitve plate boundaries

at desirvie  plate boruiade  2 pice of the earht crust coilde.  at destiue plate  bouidares  crust desrtoyed either sudducted at ocean  trench  or crumpled to fold  moniaties.  there are 3 tye of plate bondraises. 

  • ocean ocean 
  • ocenan to contient 
  • contejnt to cointne

at ocena bonadrises. 

  • 2 picses of ocean crusr coiilldes eveuanlty  one is sudbctedued beantne the other frtion  tigger earthquake 
  • subbucted  plate metls  in the mantne  truing magma 
  • the bot boyany magma rise thogth overrideisng  plates

desitr plte boruadry  (

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hotspots, guyots and atolls

hotspot  or plumes 

are area  in the mantle  that give  the rise ot coiutiose  vociatione activty in over the ridge plate.  as  covection cureent in the nantle  drag  the vocilae isakdn away  for the hotspot. 

the formation of guyots 

the ocenan flour  has in serval area chain of voailce isaldn that srtech away.  there fromer  valioce isaldne are now  surmgred  and have flta  top  like plate  are know as seamoutn and guyots. 

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gravity and heat flow patterns at constiuve plate

evdience  for the exsiting  at the old mid ridge at a construcite plate margins come form both  gravity  and heat  flow patterns. 

ecidiene for the mid lalt9ca rideg  at conste plate mairfe come form  both gravity and heat flow patterns. 

gravity pattrns 

postive anonamly  ovee the ridge  annomaly derse the futhehr away form ridge you travle/ 

heat  flow patterns 

postivle  flow annommalu over the ridge  as this higest heat flow  is- here lava is erupted at the surface  and form new land. 

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oeean to contleisen plate bouradry and heat flow

at a ocena to contne deriute plate boruadry  eg west cost of south america. 

a slab ocean to curst colldies  with contntal crust.  

the  hevaer crust  is subdcueted  draw don to  the upper mantle.  this creates  friction along  the bouradry of the 2 plate that gertate earthquak  and fold mouitnates are formed. 

subted ocena  plates  melts  in mantle and gertaed magm and fold moitunare are formed. 

hot bouannt  magma rise thought curst abosriing  cointine crsut  lower temuer and chrgaing comstion to more acid. 

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contieint to conieite derticte plate bouradry.

at a conitient  dertiuty plate bouradry. 

2 pice of cpntoilae crust coildes 

the ocena crus between  the 2 is subbcuted. 

the seidmient ocena baise are crumpled to form fold miatioense.  thses are deep earthquake  here but no volacnese beacse the curst is thick now  that any risieng magmam coools  befre it reaches  the crust. 

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