history of geology the birth of new science

8/12/2019 History of Geology the Birth of New Science

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History o f Geology

The birth of modern science:17 th and 18 th centuries

Discussions about the origin and formation of

the fossils , and the origin of MountainsNicolas Steno (1638-1686) and the law ofsuperpositionBenot de M aillet (1656-1738) and the en d ofthe biblical Earth History

James HuttAbraham Werner (1749-1817): Neptunism and

Plutonism


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The Birth of Modern Science

Origin of fossilsSince t he R oman Era, thequestion of the origin offossi l i s st ill debatedSome as sert that they ar ethe remains of animals transformed into stonesOthers argue t hat theyare the result ofspontaneous generation within the rocks layers


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Origin of fossilsThe o rigin of giant bones andthe principle of theapparition and disappearan-

ce of species i s not conceivedyetGiant bones are stillattributed to ancient giantrace of humans


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Origin of fossilsThe o rigin of giant bones andthe principle of theapparition and disappearan-

ce of species i s not conceivedyetGiant bones are stillattributed to ancient giantrace of humansUnknown species are n otconsidered as ancientorganisms, but to humaninventions or spontaneous

generative force of the earth


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Origin of fossilsVarious legends aboutfossi ls p ersisted till the 17 th centuryFor example, some f ossilswould be flying rocks , orfalling f rom the m oon , orappearing miraculouslyduring thunderstorms e tc.Spiriferida, Echinoderms (sea urchins) and

glosso w ere classifiedamong the flying fossils


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Origin of fossilsBernard Palissy n oticedthe p resence o f non livingspecies an d explained thatby overfishingNotion of lost speciesHe al so noticed thepresence o f equatorialfishes in France, which hasa t emperate cl imate an dsupposed they werebrought by m an afterfishing


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Origin of fossilsNicolas Steno laid downthe basis of modernstratigraphy a ndpalaeontologyHe demonstrated theorganic origin of fossils :Absence o f deformation ofthe m atrix co ntaining thefossils, presence of brokenshells, the organisation instrata o f the rocks, etc.


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Various legend e xisted about fossils until the17 th c entury: flying stones, falling from themoon, the s tars or from the s ky d uringthunderstorm or lunar eclipse

Only t wo serious suppositions were a cceptedas sc ientific:1. Formation in-situ by spontaneous genera-

tion or influenced by s tars ( astrology)2. Formation by transformation of once-

living organism i nto rockScientists of the 16 th and 17 th cen turies showed

that the second hypothesis was the b est

Origin of fossils


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The n otion of lost species ( species that doesnot exist any more) is suggested for the firsttime by B ernard PalissyTwo hypothesis t o explain the d isappearance

of species:1. Overfishing by humans2. Spontaneous disappearance a fter the

Deluge c aused by God's angerThe s cale o f time u sed by 16 th and 17 th centuries geologists is false but someimportant ideas o f the m odern science ar e

emergent

Origin of fossils


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Origin of fossils What were the legends about fossils?


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Origin of fossils What are the two main scientific

hy othesis to e! lain fossils?


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Origin of fossils What arguments used "eonardo da

#inci$ Bernard %alissy and &icolas Stenoto demonstrate their hy othesis?


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The Birth of Modern SciencePrinciple of original

horizontalityNicolas Steno laid downthe basis of modern

stratigraphy andpalaeontologyHe p ostulated the law ofsuperposition

He i nferred the principle oforiginal horizontalityHe tried the first hypothesisfor the T uscany mountainsformation


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The Birth of Modern SciencePrinciple of original

horizontalityThis principle states thatlayers of sediments a reoriginally depositedhorizontally u nder theaction of gravityIn the h ypothesis of an

inactive e arth all layersshould be h orizontalTilted or folded layers exist and indicate that the earth

is a ctive


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The Birth of Modern ScienceLaw of superpositionSedimentary l ayers aredeposited in a t imesequence w ith the oldeston the b ottom a nd theyoungest on the t opThe Brethren of Purity (Ikhwan Al-Safa) in the

late 10th century firstsuggested this law Avicenna i n 1027 also

wrote a bout strata o frocks and superposition


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The Birth of Modern ScienceLaw of superpositionSuggested by e arlyauthor but not appliedFormally s tated by

Nicolas Steno i n hisProdromus in 1669Based on the s tudies offossils an d the layers containing themNicolas Steno was thefirst to infer the relativeage o f stratas


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Law of superpositionUsing t he law ofsuperposi an d the

princ

horizontality , NicolasSteno made a model forthe formation of theTuscany Mountains

The p late go es from thepresent time to theorigin, i.e. from thebottom to the top



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Law of superposition1.Sedimentary deposit within

the o cean during ansubmersion episode

2.Emersion and digging o f a subterranean river bycirculation of water

3.Collapse o f the t op layer4.Submersion and horizontal

sedimentary deposit5.Emersion, digging an d

collapsing



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NeptunismThe al most ubiquitouspresence of fossils in mostfield s upport thehypothesis of NeptunismThe s tudy o f the B ible an dthe belief in the creationof the e arth in a short time by G od reinforced thistheoryThe w hole ea rth crust wasbelieved to have f ormed in

a primitive o cean



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NeptunismBenot de Maillet observedsedimentation processesnear seas and oceans andwrote a theory o f the ea rth suggesting a history ofseveral millions o f years forthe earth evolutionMountains would form bysedimentation in aprimitive o cean whichlevel is getting lower andlower



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NeptunismThis theory accep ted theformation of the ear th andcontinents as supposed byThomas BurnettIt was slightly transformedto replace o necatastrophic ev ent(collapse of the primitivecontinent in the primitiveocean) by a moreprogressive ca use(decreasing o cean)



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NeptunismHowever, the wordNeptunism wascreated by AbrahamWerner ( 1749-1817) inthe late 18 th cen turyThe gen eral theory w asthat the earth wastotally r ecovered by aprimitive oceanThe o cean level lower and allowed lands to

emerge



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NeptunismMountains formed bysedimentation ar oundsubmerged primitivemountainsOld and primitivemountains are in thecentre o f mountainchains and devoid offossilsRecent mountains arerich in fossi ls i n the

periphery



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PlutonismTheir is no fossils ingranites or basaltThese r ocks are formed

of crystals an d not ofsand or mudTwo types of rocks: sedimentary a ndplutonicGranites and basaltsmay cr oss-cut thesedimentary l ayers


f


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Plutonism James Hut

remarked discordances between thesedimentary l ayersNot all of them a rehorizontal, but theywere d eposited

horizontallyThus, some p rocess ledto their deviation,levelling and covering


h h f d


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Plutonism James Hut

first great theory of rockcycle

For him the mechanismat the origin ofsedimentary l ayersdeviation is the heat

The h eat lead to themelting o f some r ock,and the uplift ofcontinents and

mountains



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Th Bi h f M d S i


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PlutonismHutton thought thatthis cy cle co uld beeternal and infer thatthe e arth had nobeginning an d won'thave an endHe s aid we s ee no

vestige of a beginning...No prospect of an endHe w as accused ofimpiety for his assertion


Th Bi th f M d S i


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PlutonismThe t heory o f theinternal fire was notnew during t he t ime o f

James HutIt also proposed byDescartes in his theoryof the f ormation of the

earth It was also described byAthanasius Kircher toexplain volcanic activity


history of geology the birth of new science

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