GEOMORFOLOGIE
TUTORE CURS: Conf. univ. dr. Marian Ene
AGENI I
PROCESE GEOMORFOLOGICE
METEORIZAREA reprezint un ansamblu de procese fizice i
chimice prin care are loc distrugerea rocii. Eroziunea i
transportul nu sunt obligatorii, astfel nct n acest caz cea
mai mare parte a materialului rezultat rmne n locul n care
roca a fost distrus;
Meteorizarea creeaz produse (materiale) de meteorizare;
www.web/karin/mechanical-weathering-diagram&docid http://www.canadiangeographic.ca/atlas/glossary
acest proces se realizeaz la contactul atmosferei terestre
cu roca, determinnd transformarea acesteia prin intermediul
unor procese superficiale dintr-o stare stabil ntr-o stare
mobil uor de dislocat de agenii exogeni;
n funcie de mecanismul prin care se realizeaz i de
transformrile pe care le sufer roca, aceste procese sunt de
dou feluri: meteorizare mecanic (a) i meteorizare chimic
(b).
http://www.limestone-pavements.org.uk
http://www.limestone-pavements.org.uk/http://www.limestone-pavements.org.uk/http://www.limestone-pavements.org.uk/
meteorizarea mecanic (dezagregarea) se produce n
urma tensiunilor externe; fragmentarea rocii se produce fr
schimbarea compoziiei chimice a acesteia;
meteorizarea presupune, ns, existena unor fisuri iniiale n
masa rocii, fisuri n interiorul crora se vor produce ulterior
tensiuni laterale determinate de modificarea unor factori
atmosferici;
http://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.html
http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-
mountain-slope-in-caucasus-image12887389
http://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.htmlhttp://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.htmlhttp://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.htmlhttp://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.htmlhttp://dawnssedstrat.blogspot.com/2012/02/weathering-and-erosion.htmlhttp://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389http://www.dreamstime.com/royalty-free-stock-images-weathering-rocks-on-mountain-slope-in-caucasus-image12887389
agenii care determin procese de dezagregare sunt legai de
dinamica factorilor climatici (temperatur, umiditate) care pot s
genereze n interiorul fisurilor, porilor din roc tensiuni tangeniale
puternice, care vor duce la frmiarea rocii;
aceste procese sunt impuse de: insolaie, nghe-dezghe,
umezire-uscare, presiunea rdcinilor plantelor http://suhow.info/30256-definition-of-differential-weathering.html
http://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.html
insolaia; este fenomenul ce determin modificrile termice de la
suprafaa rocilor, provocnd dilatarea i contractarea termic a
mineralelor ce intr n compoziia acestora; eficiena ei este cu att mai
mare cu ct roca este mai puin protejat de nveliul vegetal sau de sol;
exist regiuni lipsite de vegetaie (deerturi) unde , ca urmare a insolaiei
puternice, temperaturile diurne oscileaz ntre 0C i 50 70C, uneori mai
mult; n timpul nclzirii are loc o dilatare a mineralelor din roc, iar n timpul
rcirii o contractare a acestora; aceste tensiuni produc crpturi a cror
profunzime este limitat de slaba conductibilitate termic a rocii; efectul
insolaiei este superficial i se produce pe adncimi de la civa milimetri la
civa centimetri (dezagregare prin descuamare); efectul tensiunilor termice
este mai mare cu ct componena mineralogic a rocilor este mai neomogen
(exemplu: mineralele mai nchise la culoare se nclzesc mai repede i se
rcesc mai greu); formele de relief rezultate sunt diverse, cum ar fi blocurile de
roc rotunjite devenite aproape sferice (cpnile de zahr din M. Mcinului
sau din jurul oraului brazilian Rio de Janeiro);
http://www.portervillecollege.edu/richardgoode/Death%20Valley%20Pictures.htm
http://www.portervillecollege.edu/richardgoode/Death Valley Pictures.htm
ngheul i dezgheul produce tensiuni laterale n interiorul fisurilor i
porilor rocii datorit creterii n volum (cu circa 9%) a apei n urma
ngheului acesteia; procesul de dezagregare prin nghe-dezghe este
eficient doar atunci cnd fisurile i porii rocilor sunt umplui cu ap ntr-o
proporie de peste 90%;
umezire uscare: dezagregarea se poate datora i presiunii de
cristalizare a srurilor; soluiile concentrate cu anumite sruri produc procese de
cristalizare a srurilor pe suprafee de strat, n fisuri, n porii rocilor n urma
evaporrii apei. O sare n momentul cristalizrii i mrete volumul i preseaz
asupra rocii (tensiuni de cristalizare);
http://www.papplewick.org/holgate/fieldwork/Processes/weathering&slopes.htm
http://www.papplewick.org/holgate/fieldwork/Processes/weathering&slopes.htm
presiunea rdcinilor plantelor exercitat n timpul creterii rdcinilor;
determin pstrarea dislocaiilor i chiar mrirea acestora (A), ceea ce duce la
creterea volumului i suprafeei pe care pot s acioneze agenii externi;
rdcinile plantelor superioare au un efect de dislocare n timpul balansrii lor de
ctre vnt (B).
http://suhow.info/30256-definition-of-differential-weathering.html
http://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.htmlhttp://suhow.info/30256-definition-of-differential-weathering.html
meteorizarea chimic (alterarea) reprezint ansamblul de procese prin care are loc
descompunerea substanelor i elementelor chimice din compoziia rocilor i formarea unor
noi combinaii chimice:
A + soluia A B + soluia B
Alterarea chimic este prezent n mod deosebit n rocile metamorfice i magmatice, roci
neomogene ce conin numeroase elemente chimice ce se combin uor cu cele din aer i ap, cum
ar fi O2 i H2O. Intensitatea de aciune a apei este condiionat de temperatur i pH-ul su;
condiiile de alterare sunt impuse de:
de alctuirea mineralogic (i chimic) a rocilor;
de gradul de fisurare i porozitate a rocilor, ceea ce determin creterea suprafeei de
contact cu apa i aerul (mediul atmosferic);
de clim i vegetaie.
Rezultatele
