How were the Caverns created?

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class="MsoNormal">Your definitte article and capital 'C' imply a

particular cave, but you don't name one. For the specific geology

and development of any individual cave you will have to read the

appropriate research papers on that region and its karst features;

but if it's a karst cave, as most are, the essentials are:

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How Caves Form in

Limestone

This is such a

common question on ‘Answers’ I wrote this single reply! The

technical terms are introduced by capital initials.

Most of the

world’s caves are Karst features, i.e. primarily in Limestone.

Karst caves need

three materials: a soluble rock like Limestone or Gypsum, water and

Carbon-dioxide (CO2). The last two combine to form a weak acid that

dissolves the limestone. For a fuller account:

The host limestone

needs to be of appropriate physical structure and raised into

hills, then subjected to reasonably consistent precipitation for

many tens or hundreds of thousands of years.

Limestone is a

sedimentary rock of which the world’s greater proportion was laid

down in warm, relatively shallow, seas. The rock was laid in

horizontal layers – Beds – separated by Bedding-planes which

generally reflect geologically-brief changes in the environment.

The suite of beds is known as a Formation, generally named after

its “type area”.

Later continental

uplift (tectonic processes) raise the formation along with its

underlying rocks, usually tilting and folding it to at least some

extent in the process. Since most rocks are brittle they cannot

take much stress, and limestone beds crack into grids of fine

fractures called Joints. The uplift and folding often also causes

Faulting – major breaks with the rock mass one side of the Fault

Plane being raised, lowered or moved horizontally past that on the

opposite side. (Note: Plane – the “Fault Line” sometimes misused as

a political metaphor is that of the fault-plane cutting the land

surface.)

Now we have the

hills, next we need rain-water that has absorbed atmospheric CO2 to

create Carbonic Acid (weak, natural soda water in fact!). It may be

augmented by acids from the soil, too. This solvent permeates

through all those joints, bedding-planes and faults; flowing very,

very slowly under considerable pressure applied by its depth, from

its sinks on the surface to its springs at the base of the

formation. In doing so, it dissolves the limestone (chemical

weathering), creating meshes of tiny micro-conduits that over many

tens of thousands of years coalesce and capture each other to form

cave passages.

Once this happens,

the rate of erosion can increase – though still to perhaps only a

few millimetres per thousand years under generally temperate

climates.

A cave, or a

series within a cave system, that still carries its formative

stream is called “Active”, and is still being developed.

Surface changes

such as the valley floor being lowered by erosion, or down-cutting

within the cave by its stream, changes the water’s route and the

original, now dried-out, stream-way is called “Fossil” or

“Abandoned”. Such passages may be filled with silt left by floods

as the main flow gradually abandons them; or may become richly

decorated with Speleothems – calcite deposits such as stalactites

and stalagmites precipitated from ground-water still oozing through

the joints in the limestone above the cave. In time such passages

may start to break down as there is no stream to dissolve away

slabs falling from the roof as permeating ground-water attacks the

rock above.

In the end,

surface lowering of the landscape as a whole, breaches and destroys

the cave. Nothing is permanent in Nature!

Caves in limestone

are also parts of Karst Landscape. i.e. a landscape developed by

the dissolution of limestone, giving surface features like Dolines,

Limestone Pavement, and in the tropics, distinctive hills such as

those represented in Chinese Willow-pattern images. ‘Karst’ is from

the Slavic Word ‘Kras’, the name for its world type-area.

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The above is

purely an introduction to a vastly more complex and subtle series

of processes, of course, and you need to refer to appropriate

text-books on geology and cave studies to learn them.

The scientific

study of caves is Speleology – embracing geology, hydrology,

Biology, Archaeology and other disciplines.

Simply visiting

caves to enjoy them for their scenery and the physical and mental

challenges they present, is called Caving, though you can’t study a

cave unless you can negotiate its obstacles. The enthusiasts are

simply Cavers throughout the English-speaking world – you see

“spelunkers” sometimes on ‘Answers’ but it's an old slang Word not

found in caving literature.

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