Rock of ages

VIDAL ROMANI, J.R. (1) YEPES TEMIÑO, J (1) FERNANDEZ MOSQUERA, D. (1) DE UÑA, E. (2) & TWIDALE, C.R. (3) (1) Ins i u o Uni e si a io de Xeolóxia "Isid o Pa ga Pondal", Uni e si y o A Co uña, 15071-A Co uña, Spain (2) Depa men o Geog aphy, Uni e si y o Vigo, 32004-Ou ense, Spain (3) Depa men o Geology and Geophysics, Uni e si y o Adelaide, Adelaide-5005, Sou h Aus alia, Aus alia ROCK OF AGES Abs ac G ani e is emplaced deep in he Ea h's c us . I cools and c ys allises and is subjec ed o he mal and magma ic e en s, and o ecu en s esses. I de elops ex u es o ab ics as well as s ain pa e ns which, as e osion b ings he ock mass nea he su ace, ind exp ession in a ious ac u e se s and sys ems. F ac u es a e a enues o weakness exploi ed by mois u e when he ock mass in e cep s he g oundwa e zone (pa icula ly in he zone 700-800 m below he land su ace). The pa e ns o hese ac u es a e imposed on he shape o he land su ace a a ious scales. Subsu ace wea he ing pa e ns a e de e mined by ac u e densi y and a he mesoscale ind exp ession, o example, in bo nha d s and a he mic o in cle s o slo s. Once exposed o epigene wea he ing and e osion bo nha d s may, depending on clima e and deg ee o exposu e, be ans o med in o nubbins o kopjes. Ancien s ains and ab ics a e exploi ed o p oduce gu e s, basins, and linea ions. Tec onism con inues so ha new sca ps and pop-ups de elop. Clima ic changes lea e behind elic ea u es alien o hei new en i onmen . Thus g ani e o ms can be assigned di e en ages: a gene ic age whe e mo phology is ela ed o pas ec onic, he mal o magma ic e en s; a p e-exposu e age whe e de eloped by subsu ace wea he ing; an epigene age whe e shaped a he land su ace; an inhe i ed age whe e shaped by p ocesses ela ed o p e ious clima ic egimes. Thus many land o ms a e mul is age. The e en s o which hey owe hei mo phology can in some ins ances be aced back a in o Ea h ch onology. (250 wo ds). Conclusions The i s p oblem in o de o unde s and he elie de eloped on g ani ic ocks is o de e mine whe he he o ms a e based on exogenous o endogenous o igin ea u es o ally o pa ially. I is also impo an o know he a e a which a ious exogenous e osi e agen s esponsible o he o ms (wa e , ai , ice) ac . The age o he o ms gi es he age o he su ace o e which hey de elop, as he e will be ound olde o ms, ob iously, o e he oldes su aces, hough all he o ms may disappea i he deg ading o he su ace bea ing hem is in ense enough and long in ime. So, i is unde s ood ha he e exis s a g ea unce ain y in geologically de ining alue, age, o igin and meaning o a su ace i we backed on he o ms de eloped o e i . Anyway, he oldes age o a o m should be logically in e ed om he pe og aphical-s uc u al his o y o he ock. The o he ages, which may be gi en, co espond o he di e en phases la e o he exposu e o he ock in su ace. Re e ences A zi, A.A., 1978. C i ical phenomena in he heology o pa ially mel ed ocks. 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