Chapter 9: Karst Landscape Karst topography Exposed limestone Dissolving of carbonate rock

Chapter 9: Karst Landscape Examples of karst regions The Burren, Co. Clare and Marble Arch, Co. Fermanagh

Chapter 9: Karst Landscape Formation Limestone is permeable Carbon dioxide (CO2) dissolves in rainwater Forms weak carbonic acid Percolates through rock – rocks dissolved by carbonation Fissures in rock become enlarged Underground drainage system develops

Chapter 9: Karst Landscape Surface landforms Limestone pavement Exposed area of limestone Rugged and bare landscape with flat areas of rock surface

Chapter 9: Karst Landscape Formation 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, limestone is dissolved Joints and cracks (i.e. bedding) are widened by the rainwater e.g. the Burren, Co Clare

Chapter 9: Karst Landscape 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

Chapter 9: Karst Landscape 2. 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 Dry valley = remains of river valley downstream from sinkhole River of resurgence = where river reappears at the surface

Chapter 9: Karst Landscape Subsurface 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

Chapter 9: Karst Landscape 2. 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 pillars hanging down from the roof of the cave Stalagmites Water droplets fall to the cave floor Over time deposition of calcite form pillars growing upward from the cave floor form directly below stalactites

Chapter 9: Karst Landscape 2. Dripstone features (continued) 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

Chapter 9: Karst Landscape 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

Chapter 9: Karst Landscape Cycle of erosion in a karst topography Three stages: Youthful Mature Old age

Chapter 9: Karst Landscape 1. Youthful stage Rivers flowing on the surface Erosion of impermeable rock Then erosion of permeable rock (limestone) Chemical weathering (carbonation) Formation of swallow holes

Chapter 9: Karst Landscape 2. Mature stage Dry valleys on the surface Sink holes

Chapter 9: Karst Landscape 3. Old age stage Weathering Removal of limestone Older more resistant rock left prominent – hums Rivers once again flow over the surface