1. No category

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
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. (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)