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
mantle(soild with semi plastice upper layer anthosmee)
layer and dicotiunites
crust is soild
mantle semo liquid uper portion (250km) otherwise soild.)
inner core liquid
layer are seroarted by bouridiase called discontituttes. it serpate layer witin the earth by commsion and state.
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.
- 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
- 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.
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
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.
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.
damge to stuster
- building meartials
- age of bulding
- type of building
- 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.
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
- loss of family meber
- shortgae of food
- 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.
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.
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.
- larges earht quake happn at dissctitue plate boruabese
- earhtquake shalow couitee plate boruadry
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
- pafice plate
- north america plate
- south america plate
- africa plate
- indo austrailte plate
- arabie plate
- antractic plate
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.
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.
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.
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
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.
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.
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.
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.
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.