LESSON 13.9 What are underground landscapes?
LEARNING INTENTION By the end of this lesson you should be able to describe some of the different types of landforms within different types of landscapes, such as karst (cave) landforms.
Tune in Did you know that the rocks that make up the karst landscape are composed of limestone and dolomite? Both are carbonate rocks (a subclass of sedimentary rocks). They are highly susceptible to a form of chemical weathering known as oxidation (a chemical reaction that causes rocks to break down due to the presence of water, oxygen or acid). 1. How do you think sedimentary rocks were formed? 2. You can see oxidation at work when you cut an apple and it turns brown. What do you think is causing oxidation? 3. Brainstorm how you think the structures shown in FIGURE 1 were formed.
FIGURE1 Lake Cave, Margaret River, Western Australia
13.9.1 What is karst? Apart from surface rivers and streams, there are vast networks of underground rivers. The result is a network of caves and channels that carve a vastly different landscape known as karst. Karst landscapes form over hundreds of thousands of years as water dissolves bedrock ( FIGURE1 ). On the Earth’s surface, sinkholes (holes), vertical shafts (tunnels) and fissures (cracks) will be evident. Rivers and streams seem to disappear, as they make their way into intricate drainage networks underground, complete with stalactites and stalagmites ( FIGURE2 ).
TOPIC13 Landforms and landscapes – diversity, significance and management 327
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