Goh Cheng Leong Chapter 8: Limestone and Chalk Landform YouTube Lecture Handouts

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  • Sedimentary rocks of organic origin from coral accumulation

  • Pure state – calcite or – soluble in rain water ( from air forms weak acid)

  • Along with magnesium called as dolomite

  • Also called karst topography – Karst district in Yugoslavia

  • Broken by precipitous slopes

  • Absence of surface drainage (most surface water is underground)

  • Streams on other rocks flow for short distance and then go underground & surface is dry

  • Water penetrates base of limestone and meets non-porous rocks it remerges on surface as spring or resurgence

Features

  • Limestone are well jointed

  • Rainwater finds the way through these cracks

  • Grikes (joints widened by chemical weathering)

  • Cracks enlarge into trenches as limestone pavements

  • Enlarged joints as grikes

  • Rectangular blocks as clints

Image of limestone topography

Image of Limestone Topography

Image of limestone topography

  • Small depression on surface by rainwater – swallow holes

  • Where rainwater sinks into limestone at point of weakness – sink holes (example, Gaping Ghyll in Yorkshire) – these grow by solvent action

  • When water sunks into limestone it etches out caverns. When roof collapses limestone gorge as Cheddar Gorge is formed

  • Swallow holes coalesce to form large hole – Doline

  • Dolines merge to form – uvala (miles along with clayey soil)

  • Yugoslavia – large depressions of hundred square miles as polje due to faulting (during rainy season floor near water table become temporary lakes while drier areas are fertile & support large villages)

Image of Topographic Watershed Divide

Image of Topographic Watershed Divide

Image of Topographic Watershed Divide

  • Streams descend through swallow holes into underground passage – with caves

  • Stalactites – from top or roofs and are downward pinnacles. Calcium carbonate is carried in solution, when water evaporates calcium carbonate solidifies

  • Stalagmites – from base – shorter, fatter and rounded

  • Stalactite and Stalagmite join to form pillars

Image of Stalactite

Image of Stalactite

Image of Stalactite

Caves – Batu Caves (Kuala Lumpur); Mammoth Caves; Kentucky & Carlsbad Cave (New Mexico, USA); Postojna Caves (Yugoslavia)

Limestone Regions

  • Causses (S. France)

  • Pennines (Britain) – Yorkshire & Derbyshire

  • Kentucky (USA)

  • Yucatan Peninsula (Mexico)

  • Cockpit Country (Jamaica)

Human Activity in Karst Regions

  • Mainly barren

  • Thin soil

  • High porosity

  • Surface drainage is absent

  • Vegetative growth is difficult

  • Poor grass and short turf

  • In tropical areas – luxuriant growth with heavy rain throughout year)

  • Scattered settlement

  • Sparse population

  • Lead occurs along with limestone

  • Used in building material for cement industry

  • West Malaysia – limestone outcrop of Kledang range & Main range is quarried for Pan-Malaysian and Tasek Cement Works

Chalk

  • Landform of chalk are different from limestone

  • Little or no surface drainage

  • Valleys once contained are now dry and called coombes

  • Low rounded hills in S & SE England

  • Called Downs in N. France

  • Covered with short turfs & woodland

  • Friable rocks – so swallow holes don’t develop