FIGURE2 Formation of a karst landscape
Volcanic rock
Disappearing stream
Acidic rainwater
Cracks in limestone
Carbon dioxide dissolves into water
Cave
Volcanic and sedimentary rock
Spring
Limestone
SkillBuilder discussion Geographical inquiry 1. Look at FIGURE2 . Explain why the stream seems to disappear. 2. What do you think causes acidic rainfall? 3. What type of rock erodes to form the karst landscape? 4. Do you think this rock would erode if the rainwater were not acidic?
Karst topography makes up about 10 per cent of the Earth’s surface; however, a quarter of the world’s population depend on karst environments to meet their water needs. 13.9.2 How are karst landscapes formed? Water becomes slightly acidic when it interacts with carbon dioxide in the atmosphere or filters through organic matter in the soil and percolates into the ground. Acidic water can dissolve soluble bedrock such as limestone and dolomite, creating cracks and fissures that allow more water to penetrate the rocks. When water reaches a layer of non-dissolving rock, it erodes sideways, forming underground rivers or streams. Over time, water creates hollows that eventually develop into caves. Some karst landscapes contain aquifers capable of providing large amounts of water.
328 Jacaranda Humanities Alive 8 Victorian Curriculum Third Edition
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