Objectives: 1. To review the terms denudation, erosion, and
weathering (freeze-thaw action & carbonation), along with
surface landforms found in karst regions. 2. To introduce students
to subterranean landforms created by chemical weathering in a
limestone region. 1A2 Geography 21 st April, 2015
Slide 2
Homework: Draw a diagram of the underground features in a karst
area and explain how these are formed. Revise for next Mondays
exam.
Slide 3
KWL What we KNOWWhat we WANT to know What we have LEARNED
Terms: Denudation. Erosion. Weathering two kinds, mechanical and
chemical. Freeze-thaw action. Carbonation. Karst landscape.
Landforms associated with chemical weathering: Limestone pavement
with clints and grikes. Swallow holes. How does carbonation take
place underground? What landforms are created by chemical
weathering beneath the surface?
Slide 4
Activity Working in pairs, complete the activity sheet prepared
for this mornings lesson.
Slide 5
How are landforms created underground? During our last lesson,
we learned that rivers dissolve limestone, too. Rivers can wear
away the joints and bedding planes of limestone rock, creating a
hole that will allow it to flow underground (swallow hole). As the
river continues to flow beneath the surface, it weathers the rock.
This weathering leads to the creation of a number of subterranean
landforms.
Slide 6
Caves & Caverns Rivers create channels as they flow beneath
the surface in limestone regions. These channels are widened by the
processes of carbonation to form caves. Some of these caves are
widened further to create large chambers called caverns. Examples
include Ailwee Caves, the Burren, Co. Clare.
Slide 7
Stalactites Water containing dissolved limestone seeps through
the rock and eventually reaches the roofs of caves and caverns.
This can evaporate, leaving behind small deposits of pure
limestone, called calcite. Over time, calcite builds up to form a
thin, hollow, icicle-like shape called a stalactite, which hangs
from the roofs of the above named landforms.
Slide 8
Stalactites StalactiteStalactite and Pillar
Slide 9
Stalagmites Droplets of water may fall onto the ground in caves
and caverns directly below the stalactites. When the water
evaporates, it leaves behind small amounts of calcite. This calcite
can build up on the ground over thousands of years to form another
icicle-like shape, called a stalagmite.
Slide 10
Pillars/Columns Over a period of several thousand years, a
stalactite and stalagmite may continue to develop until they meet,
leading to the formation of another landform known as a pillar or
column.
Slide 11
KWL What we KNOWWhat we WANT to know What we have LEARNED
Terms: Denudation. Erosion. Weathering two kinds, mechanical and
chemical. Freeze-thaw action. Carbonation. Karst landscape.
Landforms associated with chemical weathering: Limestone pavement
with clints and grikes. Swallow holes. How does carbonation take
place underground? What landforms are created by chemical
weathering beneath the surface? Formation of: Caves. Caverns.
Stalactites. Stalagmites. Pillars/Columns.