Karst Landscapes

1. Karst Landscapes 5th year Geography Ms Carr

2. Learning Outcome • Understand the processes involved in the formation of Karst Landscapes. • List examples of Karst regions. • Describe the surface and underground landforms in a Karst region. • Explain the life cycle of a Karst landscape.

3. Karst topography • Exposed limestone • Landscape created by water • Dissolving of carbonate rock

4. Examples of Karst Regions The Burren, Co Clare Marble Arch, Co Fermanagh Kras, South-West Slovenia Guilin, Guangxi Region, China

5. Limestone & Carbonation • Limestone is permeable • Rain takes in carbon dioxide as it passes through the atmosphere • Carbon dioxide (CO2) dissolves in rainwater (H2O) • Forms weak carbonic acid (H2CO3) • The carbonic acid reacts with the calcium carbonate (CaCO3) in the limestone • This forms calcium bicarbonate (Ca(HCO3)2), which is soluble in water • This solution percolates through rock • It removes the calcium carbonate • Fissures in rock become enlarged • Underground drainage system develops

6. Karst Landscapes Surface Landforms

7. Limestone pavement • Exposed area of limestone • Rugged and bare landscape with flat areas of rock surface

8. Formation of a Limestone Pavement • Carbonation (chemical weathering) • Rainwater mixes with carbon dioxide in the air • Forms a weak carbonic acid • More carbon dioxide is absorbed when the water percolates through the soil • Solution; water containing the carbonic acid dissolves the permeable limestone • Joints and cracks (i.e. bedding) are widened by this process • e.g. the Burren, Co Clare

9. Features of limestone pavements • Clint: section of a limestone pavement separated from adjacent sections by grikes • Grike: vertical crack that develops along a joint in limestone • Karren: small hollow that forms on the surface of a limestone clint

11. Swallow Holes • A river disappears underground in a limestone region

12. Formation of Swallow Holes • River reaches an area of permeable rock • Disappears down through grikes • Grikes made bigger by solution (carbonation) • Forms swallow hole (sluggas/sinkholes) • e.g. Poll nagColmin the Burren, Co. Clare

13. 2. Dry valley = remains of river valley downstream from sinkhole River of resurgence = where river reappears at the surface

14. Pairwork Quick Questions • Explain the process of carbonation. • Explain the term ‘permeable’. • Name two surface landforms in a limestone region. • Which part of the limestone pavement would you walk on? • Give two other words used to describe a swallow hole.

15. Learning Outcome • Lesson 2 • Recap on Karst landscapes & examples • Recall the surface landforms in a Karst region • Complete & Label diagram showing all Karst features • Watch video clips explaining the formation of Karst landforms • Homework; Page 84 Q 1, 2 & 3.

16. Karst Landscapes Video Clips

17. Karst Landscape Underground Landforms

18. Caves • Swallow holes – river disappears underground • Carbonation – passages form large caverns • River erodes the rock of the cave by abrasion and hydraulic action • Carbonation and solution dissolve permeable rock (limestone) • Cave develops at or below zone of saturation • e.g. Ailwee Cave, the Burren, Co. Clare; Dunmore caves,Kilkenny

19. Dripstone Features Stalactites • Drops of water containing dissolved limestone seep down through cracks/fissures in the cave roof • Drops of water lose carbon dioxide and deposit calcite • Over time deposition of calcite forms the stalactites hanging down from the roof of the cave • Stalactites are hollow mineral tubes, like drinking straws • They are very thin and fragile Stalagmites • Water droplets fall to the cave floor • Drops of water lose carbon dioxide and deposit calcite • Over time deposition of calcite form the stalagmites growing upward from the cave floor form directly below stalactites • Stalagmites are thicker than the stalactites

21. Pillars • Stalactites and stalagmites grow towards each other • Eventually join to form a pillar or column Curtains • Rainwater drips from a long crack in a cave roof forms a continuous strip of calcite

22. The Burren, Co. Clare • Covers approximately 250 square km of north-west Clare • Formed during the carboniferous period, 355 to 290 million years ago • Formed of limestone rock Features include: • Limestone pavements • Subsurface and dripstone features • e.g. Ailwee Cave

23. Pairwork; OS Map Task • OS Map of the Burren Area, page 82 • Give a grid reference for the Ailwee area • Identify the height of the limestone terrace shown on the map • Locate and identify two swallow holes found on this OS map extract

24. Cycle of Erosion in a Karst Topography • Three stages: • Youthful • Mature • Old age

25. Youthful stage • Rivers flowing on the surface • Erosion of impermeable rock • Then erosion of permeable rock (limestone) • Chemical weathering (carbonation) • Formation of swallow holes

26. Mature stage • Dry valleys on the surface • Swallow holes

27. Old age stage • Weathering • Removal of limestone • Older more resistant rock left prominent – hums • Rivers once again flow over the surface

28. Quick Revision Questions • Name the main weathering process effective on limestone • List the three parts of a limestone pavement • Name another surface landform found in a limestone region • Name four underground landforms in a limestone region • Describe a stalactite

29. Exam Questions • With reference to the Irish landscape, examine how the process of weathering has influenced the development of any one limestone feature. (30m) • Examine with reference to an example you have studied, the formation of one rock type and how it produces a distinctive landscape. (30m) • Explain with the aid of diagrams, how any two underground landforms, found in a Karst region are formed. Give a named example of each in your answer. (40m- OL)