Download 1A2 Geography 21st April, 2015

1A2 Geography
21st April, 2015
1.
2.
Objectives:
To review the terms ‘denudation,’ ‘erosion,’ and
‘weathering’ (freeze-thaw action & carbonation),
along with surface landforms found in karst
regions.
To introduce students to subterranean landforms
created by chemical weathering in a limestone
region.
Homework:
 Draw a diagram of the underground features in a karst
area and explain how these are formed.
 Revise for next Monday’s exam.
KWL
What we KNOW
What we WANT to
know
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?
What we have
LEARNED
Activity
 Working in pairs, complete the activity sheet prepared
for this morning’s lesson.
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.
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.
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.
Stalactites
Stalactite
Stalactite and Pillar
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.
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.
KWL
What we KNOW
What 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 Formation of:
take place underground?
 Caves.
 Caverns.
What
landforms
are  Stalactites.
created
by
chemical  Stalagmites.
weathering beneath the  Pillars/Columns.
surface?