Weathering in granite landscapes

Granite mineralogy

• Large irregular crystals – which is which?– Quartz– Feldspar– Biotite

• When and how was Dartmoor’s granite formed?

Granite structure

• Describe the structure of granite – how were the joints formed?

• Is granite permeable?

Granite and weathering• Granite is susceptible to many types of

weathering. Describe how the following processes denude the granite– Hydrolysis– Chelation– Freeze-thaw– Organic action

Tors

• The most characteristic landform of a granite landscape is the tor.

• What is a tor?

• Name two areas of the British Isles where granite tors are found.

Theories of tor formation

• The explanation for the formation of tors and been subject to some controversy

• There are two main theories:– Linton– Palmer and Neilson

• Draw detailed, labelled diagrams explaining the two theories.

Joint control in granite landscapes

This model shows a granite landscape inSW England viewed from above. Thereare two vertical joint sets at right angles to each other. Areas of granite with widely-spaced joints (massive zones) give ridgesand tors; areas with closely spaced joints are more easily weathered and give basins.The streams follow joints and tend to haveright-angle bends – a rectilinear drainagepattern.