5th year Geography Ms Carr Karst Landscapes 5th year Geography Ms Carr

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.

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

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

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

Karst Landscapes Surface Landforms

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

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

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

Swallow Holes A river disappears underground in a limestone region

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 na gColm in the Burren, Co. Clare

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

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.

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.

Karst Landscapes Video Clips

Underground Landforms Karst Landscape Underground Landforms

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 Zone of Saturation is the soil or rock below the water table, all spaces there are permanently filled with water

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 Over time deposition of calcite form the stalagmites growing upward from the cave floor form directly below stalactites Stalagmites are thicker than the stalactites

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

Subsurface and dripstone features e.g. Ailwee Cave 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

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

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

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

Mature stage Dry valleys on the surface Swallow holes

Older more resistant rock left prominent – hums Old age stage Weathering Removal of limestone Older more resistant rock left prominent – hums Rivers once again flow over the surface Hums- Rocks that stand out on the landscape

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

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)