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Sinkhole – Eastern Pyrenees

Limestone, its Landscape

and Caves What is limestone?

• Pure limestone is calcium carbonate (CaCO3).

• Many limestones contain visible remains of living animals – whole fossils or fragments e.g. bivalve shells or fragments, corals, algae etc.

• Bivalves, corals and many other animals remove calcium carbonate from solution and secrete it as shells, etc as protective armour etc.

• Other animals that produce calcium

carbonate hard parts include: foraminifera

(very small but numerous), crinoids,

brachiopods, cephalopods.

• Calcium carbonate can also be deposited

chemically from sea water and fresh water.

• This can be as coarse crystals (e.g. like

stalagmite) or as fine particles. This often

cements the shells etc together.

• So: Limestone is a sedimentary rock formed

by primarily by organic or chemical extraction

of calcium carbonate from water.

• The main mineral in limestone is calcite – which is relatively soft. It can be scratched with a penny.

• There may be varied impurities e.g. sand, clay, organic matter, sometimes oil.

• Calcium carbonate is highly reactive with weak acid – it fizzes releasing carbon dioxide.

• Limestone is soluble in water – especially if the water contains dissolved carbon dioxide.

• It is the solubility of limestone which causes it to produce distinctive landforms including sinkholes, caves, gorges etc

Unconformity at Horton in

Ribblesdale

(Foredale Quarry 2 km South

of Horton).

The basement rocks here are

Horton Formation (Ludlow

Series, Silurian), a fine

grained turbidite sandstone.

The overlying rocks are

Carboniferous Limestone

(Great Scar Limestone).

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East Mendip unconformity. Erosion surface cut across

Carboniferous Limestone. Jurassic Limestone on top.

Hapsford Quarry

Worm tubes bored in Carboniferous Limestone infilled with

Inferior Oolite oolitic sediment. East Mendip Unconformity.

Tedbury Camp Quarry, near Great Elm.

British Geological Survey – Free Geology Information. Just type BGS or British Geological Survey into Google or other search

engine. Look at Map Viewers – Geology of Britain.

OR OpenGeoscience.

Also get Free App for iPhone – 1:50,000 geology map of anywhere in UK.

BGS Free maps. Superficial deposits near Dalton

Yellow – Alluvium. Red = Glacio-fluvial (sands & gravels)

Blue = Till (Directly deposited by glacier ice) =old “Boulder Clay”

Brownish = no superficial deposits recorded-probably bare rock.

British Geological Survey. Free Geological maps – Dalton.

(can have as bedrock & superficial – shows what is at surface)

Alum Pot area – limestone pavement above Wilson’s Cave

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Solution forms, Eastern Pyrenees

Chert in limestone. Ordesa National Park, Spain

Solution holes in

limestone.

Road section,

Puerto Rico

• Landscapes where solubility plays an

important role are termed KARST

landscapes.

• Most commonly on limestones, but also

found on gypsum (more soluble, so

gypsum only survives at the surface in a

few areas).

• Remember Chalk is a soft limestone.

Because it is a weak rock some karst

features such as caves are limited, but do

occur.

• What are the special features that are

found:

• Underground drainage

• Dry valleys

• Sinkholes

• Caves

• Gorges

Dry karst landscape – no surface streams - all underground. Co Clare, Ireland

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Coolagh River Cave,

Co Clare.

This is where the

water is!

Surface depressions

Large SINKHOLE Braithwaite Wife Hole, Ingleborough

Different types of doline (alternate name for “Sinkhole”) (from

Farrant & Cooper, B.G.S. Geoscientist 2014)

Sinkhole – Gaping Ghyll Pothole

Rising in Clapdale - water from Gaping Ghyll

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Cares Gorge

Picos de

Europa

northern Spain

‘Normal’ rocks – limited permeability –

water runs off over the surface as

streams etc. Surface erosion of the

slopes as the same time as the valley

bottom is lowering.

Limestone landscape with

underground drainage. Water flows

through the rock so the surface

slopes can remain very steep. If a

river entrenches deep then a gorge

is formed.

Water

Table

Unsaturated zone

Saturated zone

Cavers and hydrologists use the term “Vadose” for the unsaturated zone

and “Phreatic” for the saturated zone.

Cullaun 2 Cave,

County Clare,

western Ireland.

A typical vadose

passage – vigorous

stream like a

surface stream.

Cullaun 2.

Meandering canyon

passage. Typical

vadose passage

form.

Formation of a

canyon passage –

a typical vadose

passage form.

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Typical canyon

passage with

bedding plane

enlargement at

roof level

Poulnagollum Cave - main

streamway (lower part). Co Clare

Scallops (vadose). Northern Spain.

Simple water flow and cave formation with nearly horizontal rocks.

Streams collect on impermeable rocks, and disappear

underground when they flow onto limestone.

e.g. Dales, Yorkshire (including Ingleborough)

and County Clare, Ireland.

Underground stream developed on a bedding plane,

exposed by quarrying. Ribblehead Quarry.

The pattern of water flow in water filled caves (below the water table = phreatic)

This affects the shape of the passages & chambers that are formed.

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Typical large

phreatic passage.

Las Grutas de San

Sebastian de las

Grutas, Oaxaca State,

Mexico.

From D.Gillieson,

1996

Very large phreatic tube.

17.5cm

Smaller phreatic tube. Can get a lot smaller!

Cavern

enlargement by

roof breakdown.

Stalagmite columns. Northern Spain.

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Very Large Gour pools. Cueva los Angeles Puerto Rico

Cave of San Sebastian

of the Caves

Fined for surveying “Sin permiso” – without permission.

Mexican karst.

Sacred cenote, Chichen Itza, Mexico Cenote used as a swimming pool, Yucatan, Mexico

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Bar toilet outflow next to 2 drinking

water intake pipes! Same pool.

Cenote Cave, Yucatan

Mexico

Cockpit karst, Puerto Rico (new road being cut straight across).

A landscape of hills and depressions (dolines). “Eggbox terrain.”

Camuy River Cave,

Puerto Rico

A major river,

underground for much

of its course across the

island.

Concrete catchment surface to provide water supply.

Same in Gibralter!

Cockpit country,

Jamaica.

Dyeing spores for

underground water

route tracing.

Jamaica.

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Putting in dyed spores – large rising so lots needed.

Net to catch

spores where the

water comes up –

sometimes a

rising may be in

the river bed.

Sampling a net – the spores accumulate in the rubber tube.

Stream flow near Maroon Town, Jamaica. Water flow in limestone areas often does the unexpected!

Surface

flow only. With the

underground

flow!

Sink

Rising

It would be expected

that the Malham Tarn

water flows to Malham

Cove. In fact most

goes to the Aire Head

springs, a little Malham

Tarn flood flow goes to

Malham Cove.

Most of the Malham

Cove water is from the

Smelt Mill streamsink.

Rising in flood – near Ingleton

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Same place – next day!

Pothole cave

entrance – Poll

Elva, Co Clare,

Eire.

Just dived a sump!

Meandering canyon

passage.

Cullaun 2 cave, Co.

Clare, Eire.

Cueva del

Tinganon.

Asturias, Spain.

Bivouac at the sandstone/limestone boundary, Vega de Llames, Asturias, Spain.

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Thank

you for

your

patient

attention!

Swildons Hole,

Mendip