Karst Landscapes

AS Geography

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

SURFACE LANDFORMSKarst Landscapes

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 fissure 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 (sinkholes)

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.

VIDEO CLIPS Karst Landscapes

UNDERGROUND LANDFORMSKarst Landscape

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. (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)