Karst Landscapes 5 th year Geography Ms Carr

Karst Landscapes 5 th 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 (CO 2) dissolves in rainwater (H 2 O) § Forms weak carbonic acid (H 2 CO 3) § The carbonic acid reacts with the calcium carbonate (Ca. CO 3) in the limestone § This forms calcium bicarbonate (Ca(HCO 3)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 g. Colm in the Burren, Co. Clare

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

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

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

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

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

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

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. (30 m) • Examine with reference to an example you have studied, the formation of one rock type and how it produces a distinctive landscape. (30 m) • 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. (40 m- OL)