One of the landforms formed by granite is Tors.
How are Tors formed?
A. Block Disintegration
Block disintegration usually occur in well-jointed rocks. On Cheung Chau, granite is dominant, therefore, rocks on Cheung Chau are highly susceptible to the action of block disintegration.
During daytime, rocks are expose to the baking sun, they expand due to the increase in temperature. At night, due to radiate cooling effect, the rocks are cooled rapidly and they contract. Alternate contraction and expansion of the rock cause the joints or cracks present in the rock to be widen. These lines of weakness are then exposed to erosion agent such as rain water which cause the joints to be further widen. Finally, stress builds up within the rocks and the rocks split along the joints.
B. Sheeting and unloading
Uplifting of rock also produces tors.
Rocks that far from the earth surface are under immense pressure. As denudation breaks up that rocks expose the near to the surface, the pressure from the rock above is slowly reduced. As the pressure of the sub-surface rock is reduced, the rock expand, causing joint to enlarge and cracks are produced. Further denudation exposed the rocks to the surface. This is called unloading.
As denudation continues, the rocks expand further causing large blocks of rock to break away. This process supply materials for the action of block disintegration.
(Formation of Tor model)
(The Tor theory)
(The granite landscape)
Pictures of different Tors
(cheung chau , Hongkong)
(Hawk Tor)
(Tor alteration zone)
(Cairngorm tors) with human to compare size.
INTERESTING!
Mythology has it that ...
The Tor has been associated with the name Avalon, and identified, since the alleged discovery of King Arthur and Queen Guinevere's neatly labelled coffins in 1191, with the legendary Celtic hero King Arthur. Modern archaeology has revealed a fort, dated to the 5th century.
With the 19th-century resurgence of interest in Celtic mythology, the Tor became associated with Gwyn ap Nudd, who was first Lord of the Underworld, and later King of the Fairies. The Tor came to be represented as an entrance to Annwn or Avalon, the land of the fairies.
A persistent myth of more modern origin is that of the Glastonbury Zodiac, an astrological zodiac of gargantuan proportions said to have been carved into the land along ancient hedgerows and trackways. The theory was first put forward in 1927 by Katherine Maltwood, an artist with an interest in the occult, who thought the zodiac was constructed approximately 5000 years ago. The vast majority of the land said to be covered by the zodiac was, at the proposed time of its construction, under several feet of water.
Another speculation is that the Tor was reshaped into a spiral maze for use in religious ritual, incorporating the myth that the Tor was the location of the underworld king's spiral castle.
