Granite Tors start to form when magma that has intruded into the
crust cools to form a batholith. The softer rock above the batholith
erodes away over time leaving the batholith exposed to the elements.
While the rock is cooling it starts to contract causing cracks- these
also occur when the batholith is exposed and pressure is released.
The cracks in the Granite rock are made worse by the process of
freeze-thaw weathering, this is the process where water gets into
the cracks in the rocks and freezes when the temperature drops,
expanding by 9%, this repeated process causes the cracks in the
rock to widen. This process affects the Tor more where the joints
are closer together.
As this freeze-thaw weathering continues bits of Rock start to
break off, the name for these pieces of rock is scree.
This type of weathering leaves the Tor with certain characteristics:
1. The joints also become visible in the Tor,
2. The Tors edges are smooth and round.
Horizontal Bedding Planes
Smooth Round Edges
Case study: Dartmoor
Dartmoor has many Tors and is a popular popular place with
Most of the
Dartmoor Tors are
located in the
park, this makes it
an ideal place to
visit for tourists.
Examples of Dartmoor Tors: