Tor
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
A tor is a rounded pile or stack of boulders that stands out on a hilltop. It forms in granite and similar rocks that have joints (natural cracks). Weathering works its way down these joints, mainly through thermal expansion (rock swelling when heated by day and shrinking when cooled at night). The blocks between the joints get rounded. Later the loose weathered debris is washed or blown away, and the hard, rounded boulders are left standing. Tors show how joints control the way a rock breaks down.
Example
The boulder-strewn hills around Hampi in Karnataka, on the Tungabhadra river, are a well-known Indian tor landscape. Rounded granite boulders sit in heaps and balance on top of one another.
Don't confuse with
- Exfoliation dome: a single large, smooth granite dome. It forms mainly by unloading (buried rock expanding upwards once the rock above is removed). A tor is a pile of separate boulders that forms mainly by thermal expansion along joints.