The formation of 'tors' on small rocky hills is associated with which among the following?
- A.Granite
- B.Limestone
- C.Alluvial
- D.Dolomite
Correct answer
Explanation
The correct answer is A, Granite. Tors are piles of rounded, weathered blocks standing on hilltops, and they form typically in granite.
Granite cools deep underground and develops a network of joints, or cracks. While the rock is still buried, water seeps along these joints and rots the granite chemically, while the solid cores between the joints stay hard. When the overlying material is removed by erosion, the loose, rotted rock is washed away and the sound blocks are left stacked on top of one another as a tor. Dartmoor in south-west England is the classic example, and similar boulder hills are common on the granite of the Deccan around Hyderabad and Bengaluru.
B is wrong because limestone dissolves in rainwater and forms karst features such as caves, sinkholes, stalactites and stalagmites. C is wrong because alluvium is loose river sediment and cannot stand as rock outcrops. D is wrong because dolomite, a carbonate rock like limestone, also weathers mainly by solution into karst forms.
Exam tip: tors, granite; karst, caves and sinkholes, limestone; inselbergs, residual hills of hard rock in deserts.
Practice Questions
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