6 Weathering Processes and Landforms CHECK YOUR LEARNING
1. How is carbonic acid formed? 2. What makes limestone permeable? 3. Explain the process of ‘carbonation’. 4. How does ‘oxidation’ occur? 5. How is shale affected by the process of hydration? 6. How is kaolin formed? 7. Name one mineral that is not affected by hydrolysis. 8. What part do animals play in biological weathering?
Distinctive Irish Landscapes Formed by Weathering
Granite landscapes Example: Three Rock Mountain (Fig. 6.9)
Granite found in the Wicklow Mountains was formed during the Caledonian mountain building period approximately 400 million years ago. During the folding process, molten magma intruded into a large space in the upfolds under the earth’s surface. Protected from the elements of weather by overlying layers of slate and quartzite, it cooled slowly to form a hard rock with large crystals of quartz, feldspar and mica. Over time, the granite became exposed as the overlying rock was worn down by weathering and removed by rivers and ice.
The removal of the overlying rock reduced the pressure exerted on the newly exposed granite allowing it to expand. This created stresses on the rock which led to the formation of joints and bedding planes. Water was then able to penetrate into the rock, leading to further weathering by freeze-thaw action and hydrolysis. The continuation of these processes over millions of years has led to the formation of rounded hills with tors at the summit.
KEYWORDS tors
karst landscape Burren
limestone pavement grikes clints
karren fluting
swallow hole disappearing stream resurgence dry valley doline turlough dripstone
ailwee caves percolation evaporation salcite
stalactite
stalagmite pillar curtain cavern
Chapter 5: Rocks
A-Z
Tor: A large block of rock that has been weathered more slowly than its surroundings.
