Outcroppings of granite can weather to characteristic "Tors", large free-standing rocky outcrops that rise abruptly from the surrounding smooth and gentle slopes. Tors occur where joints in the granite matrix are widely spaced. After weathering core blocks survive and remain above the background surface. Tors can be monolithic, but are more usually subdivided into stacks. Each stack can comprise several tiers or pillows, which may become separated. Rocking pillows are called logan stones.
The slopes above the township of Palmer are well known for huge tors covering an extensive area. The granites are of various types including a fine grained variety and a coarse prophyritic type, both are pinkish. The area of granite tors is approximately 5 square kilometres. The granite has been dated at 490Ma by rubidium/strontium isotopic methods. The local landform is comparable to the landscape feature in the Northern Territory know as "The Devil's Marbles".
At GZ you will see a group of tors on a hill. You are welcome to log a "Found it" log when you message or email the answers for the following questions. any "Found it" logs without the answers being sent will be deleted.
1. There is massive pillow balancing on the top of the pile. How many points of contact does the balancing rock have? Why?
2. The tors are preferentially coated with lichen on one side. Which side? Why?