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

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 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?

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 StalactiteStalactite 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 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.