Karst Processes and Topography
Karst and Karst Topography
•The word ‘karst’ is German form of the Yugoslavian
term ‘Kras’ means “bare stony ground”
• Named after a region in Slovenia, partially extending
into Italy, where the first scientific research of a karst
topography was made
• In modern Geomorphology the term refers to any
landscape formed by dissolution of the underlying
bedrock
•This is characterized by distinctive landforms which
don’t typically occur in any other circumstance
Major Karst Regions of the
World
 Karst topography is characterized by
subterranean limestone caverns, carved by
groundwater
 The Serbian geographer Jovan Cvijić's
publication Das Karstphänomen (1893), based
on his studies in the Dinaric Kras region,
 established that rock dissolution was the key
process and that it created most types of
dolines, "the diagnostic karst landforms."
 The Dinaric Kras thus became the type area
for dissolutional landforms and aquifers
 the regional name kras, Germanicized as
"karst," is now applied to modern and paleodissolutional phenomena worldwide
 Cvijić related the complex behavior of karst
aquifers to development of solutional
conduit networks and linked it to a cycle of
landform evolution
 Cvijić defined two main types of karst
area, holokarst, wholly developed, as in the
Dinaric region along the eastern Adriatic
and deeper inland in the Balkan Peninsula
 and merokarst, imperfectly developed with
some karst forms, as in eastern Serbia.
 Karst landforms are generally the result of
mildly acidic water acting on soluble bedrock such
as limestone or dolostone
 The carbonic acid that causes these features is
formed as rain passes through the atmosphere
picking up CO2,which dissolves in the water
 Once the rain reaches the ground, it may pass
through soil that may provide further CO2 to form
a weak carbonic acid solution: H2O + CO2 →
H2CO3.
 Recent studies of sulfates in karst waters
suggests sulfuric and hydrosulfuric acids may also
play an important role in karst formation.
 This mildly acidic water begins to dissolve the
surface and any fractures or bedding planes in the
limestone bedrock.
 Over time these fractures enlarge as the bedrock
continues to dissolve
 Openings in the rock increase in size, and an
underground drainage system begins to develop,
allowing more water to pass through and
accelerating the formation of underground karst
features
 Somewhat less common than this limestone karst
is gypsum karst, where the solubility of the mineral
gypsum provides many similar structures to the
dissolution and redeposition of calcium carbonate
Factors affecting Karst Regions
Solubility of Limestone
- percent calcite
Climate
- Temperature and Moisture
Structure of Limestone
- joints, fractures, porosity,
Mineralogy/lithological content
- % solubility of the rock
Vegetation/Non-carbonate Geology
- acidity (pH) of groundwater
Atmospheric CO2
- affects solubility of Carbonates
Karst Landforms
 The karst landscape may have a variety
of large or small scale features both on
the surface and beneath
 On exposed surfaces, small features may
include flutes, runnels, clints and grikes,
collectively called karren or lapiez
 Medium-sized surface features may
include sinkholes or dolines (closed
basins), vertical shafts, disappearing
streams, and reappearing springs
Sinkholes
 Large-scale features may include limestone
pavements, poljes and blind valleys
 Mature karst landscapes, where more
bedrock has been removed than remains,
may result in karst towers or
haystack/eggbox landscapes
 Beneath the surface, complex underground
drainage systems (such as karst aquifers)
and extensive caves and cavern systems
may form
Limestone Pavements
 How limestone pavements form
 Limestone is a hard sedimentary rock consisting of
calcium carbonate, formed by the deposition of
plant and animal remains on the sea floor
 It is thus known as a calcareous rock
 Limestones often contain the visible remains
(fossils) of shells and corals.
 As limestone is a sedimentary rock, it is laid down
in layers or ‘beds’ separated by ‘bedding planes’
which are caused by changes in deposition rates or
content of material deposited.
Limestone Pavement
Pavement shattered
by long exposure
Clints And Grikes
 Due to the solubility of limestone, limestone
pavements are associated with some very curious and
unusual landforms.
 The most characteristic surface feature of limestone
pavements is their division into blocks, called clints,
bounded by deep vertical fissures known as grikes.
 Clints and grikes form under relatively deep cover of
soil where water, carrying carbonic acid which is
formed from dissolved carbon dioxide as well as
organic acids from decaying vegetation, picks out
vertical lines of weakness (joints) in the rock.
 These fissures widen over the years as the acidic
water preferentially attacks the lines of weakness.
Grikes take many thousands of years to form under
the soil as the rate of solution is slow.
Runnels, Pits and Pans
 As well as clints and grikes, limestone pavements also
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have a number of characteristic surface formations
These are known as runnels, pits and pans and take
different forms depending on the structure of the
pavement on which they form.
Runnels are gutter-like channels eroded out of the
surface of the limestone which drain into grikes
The formation of runnels takes place under a shallow
layer of soil.
Runnels formed on steeply sloping limestone are
usually close together and parallel, whereas runnels
forming on gentle slopes take dendritic or branched
forms which can be looked at as a miniature river
system.
Rills, Pits
and Pans
 Pits and pans are small scale solution features (i.e.
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formed by water and acids dissolving the limestone)
found on the tops of clints
Pits are deep and free draining into the
subterranean limestone drainage system
Pans are shallow, have an impervious base and hold
water
Both of these features also form under shallow soil
cover
Some research indicates that the deeper features
can be formed by humic acid from the roots of
trees resting against the limestone and dissolving it
into the characteristic round bottomed features of
pits and pans
What are ‘Karrens’?
 The limestone features described above have specific
scientific names and are known as ‘Karren’.
 Karren is a general term used to describe the total
complex of superficial micro-solutional features of
soluble rocks such as limestone and gypsum.
 Karren are particularly common on limestone
pavements.
 Karren forms include sharp-ridged grooves
(rillenkarren) and their larger, elongated cousins
(rinnenkarren), as well as rounded runnels formed
beneath a soil cover (rundkarren). Other forms
include the ubiquitous solutional hollows (kamenitzas),
grikes (kluftkarren), clints (flachkarren), and
horseshoe shaped stepped structures (trittkarren).
• Pseudokarst is the term for karst-like
development in non-carbonate lithology
that exhibits characteristics similar to
karst landscapes, but which lack dissolution
as a primary means of landscape formation
• Pseudokarst refers to landscape features
similar in form or appearance to karst
features, but are created by different
mechanisms.
• Examples include lava caves
and granite tors and paleocollapse features
Karst Collapse Landforms
•
Sinkhole or Doline comes in a variety of shapes
most often funnel shaped forms
• as material above a cavity becomes too thin to
support the weight
• they are sometimes filled with colluvium from
edges of feature and can also form circular lake
• often entrances to caves are found in sinkholes
• Compound sinks form Uvalas: several sinkholes
coalesce to form a larger structure (sometimes a
kilometer)
• Occasionally, uvalas are floored with alluvium
derived from subterranean streams
Formation of a Doline
Dolines or Sinkholes
 Dolines, or sinkholes are enclosed depressions
 solution doline: Funnel-shaped doline formed by the
progressive subsidences as solution progresses along a
joint or joint intersection. Regolith drapes the floor
of the doline.
 Subsidence doline: Similar to solution doline but
overlying soil has washed into a subsuface cave
system.
 collapsed doline: Steep-sided sink formed by
collapse into a subterranean cavity. An underground
cavern forms. Eventually the overlying rock is longer
collapses.
Subsidence
Doline
Collapsed
Doline
Sinkholes
A Sinkhole (cockpit) in Central America
The Surface Collapses to Form a Doline
Karst
features
in
Florida
Karst
terrain in
Australia
- a karren
plain with
blind valleys
and numerous
sinkholes
A doline (sinkhole)in Winterpark, FL
Karst Landforms- stream features
• chaotic or deranged drainage patterns
• few, if any, through flowing streams in karst regions
often exhibit what are called blind valleys
e.g., Lost river, tributaries and other surface streams in
the Mitchell plain,
• streams disappear into a swallow hole called a ponor, a
swallet, or a sink
•often reappear as a karst spring or a groundwater rise
-Orangeville rise;
-Wesley Chapel Gulf rise
Drainage in a
Karst region in
Europe
-flooded and
backed up into
the overflow
channels
- polje
A rise of a subterranean stream
Solution pan on a karren in the southwestern USA
Karst landforms- denudation
often large tracts of limestone karst terranes are
devoid of unconsolidated material
these areas are called Karrens
Often have solution enhanced vertical fracture and
joints sets
they can be filled with debris from dissolution
or devoid of residuum
known as grikes, kluftkarren or solution grooves
Grikes or Kluftkarren - solution
enhanced vertical fractures
the grikes divide the surface into
distinct pieces referred to as Clints
Closeup of a Karren with grikes
Soils developed in karst regions
These regionscommonly develop a thick red cap
called terra rosa
Their origins are debated and may be site
specific
They are composed of clay and are rich in iron
Commonly thought of as leftovers after intense
leaching of surface rock
May also have contribution by loess and other wind
transported sediments
Less commonly develop another type of soil that is
thin, very permeable and porous called rendzinas
allow extreme infiltration, are loamy with pieces of
residual limestone
Karren with
Grikes in Ireland
Grikes or cutters, filled with terra rosa,
shown in cross-section in a roadcut
Karst terraines in high humidity regions
forms a variety of spectacular landforms
Towers, Mounds and Cockpits
-erosional remnants of thick sequences of
limestone that have been greatly degraded
Cockpit karst region in Jamaica
Tower karst
in S.E. China
Tower Karst in S.E. China
Mitchell Plain and Chester Escarpment
Sinking stream in karst area of Kentucky
Sinkhole plain in the Kentucky equivalent of the Mitchell Plain
Limestone Caves
 A limestone cave or cavern is a natural cavity
that is formed underneath the Earth’s surface
that can range from a few metres to many
kilometres in length and depth.
 Most of the world’s caves, including those at
the Cradle of Humankind, are formed in porous
limestone.
 Over millions of years, acidic groundwater or
underground rivers dissolve away the limestone,
leaving cavities which grow over time.
Limestone Cave
Formation of
Limestone
Caves
 Early life forms appeared in the oceans about 3.8-
billion years ago.
 These were single-celled, blue-green algae, called
cyanobacteria, which made their own food
through photosynthesis, releasing oxygen into the
atmosphere in the process.
 Dolomitic limestone, a sedimentary rock, was
formed over millions of years through chemical
reactions generated by these early organisms.
 With movements within the Earth’s crust, the
sedimentary dolomitic limestone eventually
became exposed on dry land.
 As time passed the limestone, which is permeable and
soluble, was eroded by water.
 Weak carbonic acid in rainwater, reacting with the
chemicals in the rock, dissolved and eroded away the
limestone as the water filtered into the underlying
depths of sediments.
 Large hollow solution cavities were formed in the
limestone in this way.
 Many cavities occur at various depths in a cave
system due to the continual seepage and flow of the
mildly acidic water through the deposits, while
underground rivers may eventually carve their way
through a mountainside, creating openings and
entrances to the outside.
Underground River
 Many beautiful structures – including stalagmites
and stalactites – form inside caves as carbonic
acid, carrying limestone, drips through cave roofs
and onto their floors.
 Structures inside a cave may require millions of
years to develop.
 Some of the geological structures that may
develop inside a cave include:
 Speleothem
 “Speleothem” is a general geological term for a
deposit of calcium carbonate in a cave, including
formations such as stalactites, stalagmites and
flowstones.
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 Flowstone
 Flowstones are speleothems (deposits of calcium
carbonate) on the walls or floor of a cave formed
from a gradual flow of water over a relatively
broad area.
 Stalactite
 The term stalactite comes from the Greek
work stalaktos, which means “dripping”, because
these other-worldly formations “drip” from the
roofs of limestone caves.
 Essentially, water reacts with carbon-dioxide to
form carbonic acid. It then seeps slowly through
the roof of the cave, depositing calcium
carbonate, which hardens and builds up over time
to form a stalactite.
 Stalagmite
 Stalagmites are corresponding formations on the
floor of caves to stalactites. Stalagmites rise
from the floor in a build-up of calcium carbonate
over time, from mineral-bearing water dropped
from the roof of the cave. The term stalagmite
comes from the Greek word, stalagma, to “drop”.
 Column
 Sometimes, stalactites and stalagmites meet,
forming a pillar or column of rock-hard calcium
carbonate.
 Helictite
 A formation of calcium carbonate in a cave that
grows in a twisted, curled fashion, like a helix
(hence the name), seemingly defying the laws of
gravity.
Limestone
Columns