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ON THE DEFORMATION OF ROCKSSteven Wojtal (Oberlin College, US) disc sses rock deformation !

T"e deformation o# rock generates individ al $acrosco%icstr ct res s c" as #ract res, #a lts, and #olds, as &ell as$a%%able %atterns o# str ct res t"at indicate t"e relative $otion

o# 'tectonic %lates! Deformation also %rod ces distinctive#eat res t"at %ervade roc s at $esosco%ic and $icrosco%ic scales! T"ese '#abrics are de ned b* distorted 'sedi$entar* or 'igneo s#eat res or b* %re#erred orientations o# $ineral grains orres"a%ed rock #rag$ents! Over t"e %ast + *ears, geologists "avedevelo%ed increasingl* %recise -.di$ensional c"aracteri/ations o#rock str ct res and #abrics in di0erent geologic settings!1 ring t"e sa$e interval, geologists "ave sed a gro&ing bod* o#e2%eri$ental data, better $at"e$atical descri%tions o#dis%lace$ent and velocit* elds associated &it" rock str ct res,and t"eoretical anal*ses o# t"e $ec"anics o# de#or$able $aterials

to inter%ret str ct res and #abrics and, in so$e cases, todeter$ine t"e d*na$ics o# rock deformation ! 3$ong t"e $an*tec"ni4 es in $odern str ct ral geolog*, t"e $at"e$aticala%%roac" o# contin $ $ec"anics is t"e t"read t"at &eavestoget"er st dies o# %rocesses at di0erent s%atial and te$%oralscales5 #ro$ individ al $ineral grains to regional deformation totectonic %lates, and #ro$ instantaneo s dis%lace$ents li eeart"4 a e sli% to $ove$ents ta ing $illions o# *ears!...........SC6 7 8 79-58+9:...........

Notes5!!! !!! 'tectonic %lates5 T"e ter$ ;lit"os%"ere; re#ers to t"eo ter la*er o# t"e Eart", co$%rising t"e cr st and %%er $antle,and e2tending to a de%t" o# + to : ilo$eters! T"e traditionalvie& o# tectonics (c"anges in t"e str ct re o# t"e Eart"

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...........SC6ENCE.WEEK 7 Nov 7 8 "tt%5>>science&ee !co$ --sir freddieWar is an ugly thing, but not the ugliest of things; the decayedand degraded state of moral and patriotic feeling which thinksnothing worth a war, is worse. A man who has nothing whichhe cares more about than he does about his personal safety isa miserable creature who has no chance at being free, unlessmade and kept so by the exertions of better men than himself.--John Stuart ill

A balanced diet is a cookie in each hand.

Penyelidikan Deformasi

!enyelidikan deformasi dimaksudkan untuk mengetahui perubahan bentuk yang ter"adi

akibat adanya dorongan magma dari dalam dapur magma #pembubungan$ sehingga

ter"adi penggembungan tubuh gunungapi pada saat gunungapi akan meletus. Setelah

ter"adi letusan biasanya tubuh gunungapi tersebut akan mengempis kembali, bahkan

sering lebih kecil atau di bawah kondisi semula. !erubahan bentuk tersebut ber%ariasi

antara &' cm ( )m bahkan *. St. +elens mencapai m hari selama hampir minggu

sebelum meletus pada bulan ei )/0'. 1engan pengukuran yang teliti dan

berkelan"utan menggunakan tiltmeter yang peka maka perubahan tersebut dapat

diukur.

!engukuran deformasi "arak hori2ontal di 3angkubanparahu dilakukan dengan caramobile dan permanen dengan menggunakan 4ange aster 555 dan 1istomat #15 '$.

6intasan ter"auh pengukuran "arak hori2ontal adalah antara 7awah 8aru -- *unung

alang dan 43-) ( *unung alang. 9ntuk mengetahui kemampuan peralatan distomat

telah digunakan pengukuran terhadap "arak lintasan 43 ) ( *. alang dengan "arak

:.:0&./ < mm dan Wates 743 55 se"auh .

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