Karst Landscapes 5th year Geography Ms Carr Learning Outcome



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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

SURFACE LANDFORMS

  • Karst 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

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.

  • 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 LANDFORMS

  • Karst Landscape

Caves

    • 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:

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

  • Cycle of Erosion in a Karst Topography
    • Three stages:
      • Youthful
      • Mature
      • Old age

Youthful stage

  • 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

  • Mature stage
    • Dry valleys on the surface
    • Swallow holes

Old age stage

  • 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)


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