Plate tectonics and seafloor.pptx

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Plate Tectonics and Sea

foor SpreadingSalim Shehzad

BS Geology/ Geophysics

Bahria University, Islamabad



Otline

Plate tectonics!evelopment o" Plate Tectonic

theory

#cceptance o" Plate tectonics



Theory o" Plate Tectonics

Plate tectonics $ plate * plates of the lithosphere;tekton * to bild% is a ni"ying theory in geology&

#ccording to the theory o" plate tectonics, theotermost portion o" 'arth is composed o" thin,rigid plates that move horizontally (ith respectto one another, li)e icebergs foating on (ater&

#s a reslt, the continents are mobile and moveabot on 'arth*s sr"ace, controlled by "orcesdeep (ithin 'arth&



Plate Tectonics +&

The interaction o" these plates as they movebilds "eatres o" 'arth*s crst $sch asmontain belts, volcanoes, and ocean basins%&

or e-ample, the tallest montain range on 'arthis the .imalaya ontains that e-tend throghIndia,0epal, and Bhtan&

The .imalayan montain range contains roc)sthat (ere deposited millions o" years ago in ashallo( sea, providing testimony o" the po(erand persistence o" plate tectonic activity&



.istorical 1onte-t

1ontinental !ri"tIn 2345, rancis Bacon (rote

abot certain correspondence

bet(een shorelines on either sideo" the Soth #tlantic&

.is idea (as re6ected byscienti7c commnity at that time&



1ontinental !ri"t+&

#l"red 8egener, a German eteorologist,proposed the idea in 2924 that continentsare mobile&

8egener sggested that dring the geologicpast, the continents collided to "orm a largelandmass, (hich he named Pangaea $pan :

all, gaea : 'arth%&

Pangaea (as srronded by a hge ocean,

called Panthalassa $pan : all, thalassa : sea%



Sper 1ontinent



atching Se;ence o" <oc)s andontain 1hains

<oc)s "rom

#ppalachianontain in 0orth#merica match (iththose o" 1aledonianontain in 'rope



it o" 1ontinents

The coastlines oneither side o" #tlanticocean 7t together li)e

a 6igsa( pzzle&

# more accrate 7t o"continent (as

achieved in 2935sing continentsedges sbmerged inocean at a depth o"

4555 meter



Glacial #ges and other 1limatic 'vidence

=55 million years old glacialsediments (ere "ond inIndia, #"rica and soth#merica&

The present position o"these contries does notspport (ide glaciations&

T(o possibilities> (orld(ideice age $highly nli)elyconsidering coal deposit o"this age in 'rope and#merica%

These continents are



Organisms !istribtion



Ob6ections to 1ontinental!ri"t

8egener*s hypothesis received hostilecriticism becase o" mechanism heproposed "or continent dri"t&

8egener proposed that continentsplo(ed throgh the ocean basin to

reach their present position& The"rontal edges o" continent de"ormedinto montain de to this drag&



0e( 'vidence "or 1ontinent !ri"t

#"ter the 8orld II, moderntechnology has enabled to e-plorethe ocean&

0e( evidence comes in the "orm o"

Pattern o" earth;a)es

geomagnetismseafoor spreading

#ge o" ocean foor



Pattern o" earth;a)es

In 29=?, a @apanese scientist, Aiyoo 8adati,speclated that earth;a)es and volcanoesnear @apan might be associated (ithcontinental dri"t&

In 295, seismologist .go BenioC plottedthe locations o" deep earth;a)es at theedges o" the Paci7c&

.is charts revealed the tre e-tent o" thePaci7c <ing o" ire, a circle o" violentgeological activity srronding mch o" the

Paci7c Ocean&



8orld(ide locations o"earth;a)es



Geomagnetism

Some minerals, li)e magnetite, )eeprecords o" earth magnetic 7eld&

Stdies o" igneos roc)s on continentand ocean have sho(n great variation inthe orientation o" magnetic poles&

Symmetrical strips o" normal andreverse polarity (ere "ond along idOceanic <idges&



Geomagnetism



ineral Aeep <ecord o" 'arthagnetic ield



agnetism at Sea loor



Sea loor Spreading

In 2935, US Geologist .arry .ess proposedthe idea o" sea foor spreading&

.e sggested that ne( ocean crst (as

created at the ridges, split apart, moveda(ay "rom the ridges, and laterdisappeared bac) into the deep 'arth attrenches&

.e presented the mantle convection cellsas a mechanisms o" ocean foor movement&





.o( "ast is the sea foorspreadingD

Satellite GPS measrement

◦ It depends on locations

◦ 4E25 cm/year

Size o" ocean basin and the age o"crst

◦ The age o" old Paci7c crst is 255Fmillion years

◦ The (idth o" ocean basin is abot

25,555)m

10,000 km

100 million years=

107 m

108 years= 0.1 m/year



#ge o" ocean foor

In the late 2935s, an ambitios deepEsea drillingprogram (as initiated to test the e-istence o" seafoor spreading&

One o" the program*s primary missions (as todrill into and collect ocean foor roc)s "orradiometric age dating&

I" sea foor spreading does indeed occr, then theyongest sea foor roc)s (old be atop the midEocean ridge and the ages o" roc)s (old increaseon either side o" the ridge in a symmetric pattern&



+ +& + +&

Thosands o" radiometrically ageEdated samplessho(s the ocean foor is youngest along themid-ocean ridge, (here ne( ocean foor iscreated,

and The age o" roc)s increases (ith increasing

distance in either direction a(ay "rom the a-is o"the ridge&

The symmetric pattern o" ocean foor agescon7rms that the process o" sea foor spreadingmst indeed be occrring&



#ge o" Ocean loor



#cceptance o" Theory

The accmlation o" lines o" evidence inspport o" moving continents has convincedscientists o" the validity o" continental dri"t&

Since the late 2935s, the concepts o"continental dri"t and sea foor spreadinghave been nited into a mch moreencompassing theory )no(n as plate

tectonics, (hich describes the movement o"the otermost portion o" 'arth and thereslting creation o" continental and seafoor "eatres&



Plate Tectonics





Testing the TheoryE.otspot#reas o" intense volcanic activity

that remain in more or less thesame location over long periods

o" geologic time and arenrelated to plate bondaries arecalled hotspots.

'-ample, the contining volcanismin ello(stone 0ational Par) and

.a(aii are cased by hotspots&



Hot Spots ?



Coral Reefs



ormation o" Seamonts and Tablemonts



HestionsDD

Plate tectonics and seafloor.pptx

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