Karst Landscapes
5th year GeographyMs 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
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 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
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)