K
KARST PROCESSES AND ESTUARINE COASTLINES
John E. Mylroie
1
, Michael J. Lace
2
, Patricia N. Kambesis
1
and Joan R. Mylroie
1
1
Department of Geosciences, Mississippi State
University, Mississippi State, MS, USA
2
Coastal Cave Survey, West Branch, IA, USA
Synonyms
Coastal caves; Limestone dissolution
Definitions
Karst is a landscape created by dissolution of soluble rock,
made up of caves, springs, sinkholes, sinking streams, and
unusual rock sculpture.
Karren refers to the various etchings, carving, and
sculpting of soluble rock by dissolution; these features
are in the decimeter to meter scale.
Carbonates are sedimentary rocks consisting of calcium
and/or magnesium combined with CO 3
¼ .
Flank margin caves are caves developed by mixing dissolution within the margin of the freshwater lens.
Sea or littoral caves are caves produced by wave energy
and bioerosion on rocky coasts.
Syndepositional caves are caves produced within
a soluble rock as that rock is being deposited.
A hybrid cave is a cave developed by one process,
overprinted by a second process, such as a flank margin
cave overprinted by littoral processes.
Introduction
Soluble rocks are common on coastlines around the world.
These soluble rocks are primarily limestone (CaCO 3 ) and
related rocks like dolostone (CaMg[CO 3 ] 2 ) because gypsum (CaSO 4 · 2H 2 O) and halite (NaCl) are too soluble
and are quickly removed. In the tropics and subtropics,
limestones (called carbonates to refer to all the common
limestone and dolostone types) are being deposited today
and tens of thousands of kilometers of coastline at low latitudes consist of these deposits (Wilson, 2012). At higher
latitudes, older limestones are often present on the coast
for long distances, such as along the Adriatic Sea. The soluble nature of limestones means they can dissolve to form
a myriad of landforms collectively named karst: caves,
springs, sinkholes, sinking streams, and unusual rock
sculpture called karren (e.g., Ford and Williams, 2007;
Palmer, 2007). The coastal environment creates a novel
karst setting resulting from the outflow of fresh groundwater of the freshwater lens and the land mixing with salt
water invading from the sea (Figure 1a) (Scheffers et al.,
2012). The mixing of these two waters, even if both are
initially saturated with CaCO 3 , results in brackish water
that is capable of additional dissolution (Figure 1b). The
dissolution of limestone bedrock in the coastal mixing
zone is accelerated compared to that done in continental
interiors. The signature landform of the carbonate coastal
environment is the flank margin cave, so named for its
development by mixing dissolution in the discharging
margin of the freshwater lens, under the flank of the
enclosing landmass (Mylroie and Carew, 1990). Flank
margin caves are part of the Carbonate Island Karst
Model, or CIKM (Mylroie and Mylroie, 2007), developed
to explain the various karst processes and phenomena that
occur in carbonate coasts. Carbonate coasts develop
a unique type of karren influenced by the youthfulness
of the rock, boring and grazing by organisms, wave action,
and mixing of sea and fresh waters; see Taboroši and
Kázmér (2013) for a full and complete review of coastal
karren.
Flank margin caves range in size from voids only a few
meters across to extensive systems with 20 km of linear
survey (Figure 2). They form very rapidly, and on many
carbonate coasts fossil caves above modern sea level, with
M.J. Kennish (ed.), Encyclopedia of Estuaries, DOI 10.1007/978-94-017-8801-4,
© Springer Science+Business Media Dordrecht 2016
KARST PROCESSES AND ESTUARINE COASTLINES
John E. Mylroie
1
, Michael J. Lace
2
, Patricia N. Kambesis
1
and Joan R. Mylroie
1
1
Department of Geosciences, Mississippi State
University, Mississippi State, MS, USA
2
Coastal Cave Survey, West Branch, IA, USA
Synonyms
Coastal caves; Limestone dissolution
Definitions
Karst is a landscape created by dissolution of soluble rock,
made up of caves, springs, sinkholes, sinking streams, and
unusual rock sculpture.
Karren refers to the various etchings, carving, and
sculpting of soluble rock by dissolution; these features
are in the decimeter to meter scale.
Carbonates are sedimentary rocks consisting of calcium
and/or magnesium combined with CO 3
¼ .
Flank margin caves are caves developed by mixing dissolution within the margin of the freshwater lens.
Sea or littoral caves are caves produced by wave energy
and bioerosion on rocky coasts.
Syndepositional caves are caves produced within
a soluble rock as that rock is being deposited.
A hybrid cave is a cave developed by one process,
overprinted by a second process, such as a flank margin
cave overprinted by littoral processes.
Introduction
Soluble rocks are common on coastlines around the world.
These soluble rocks are primarily limestone (CaCO 3 ) and
related rocks like dolostone (CaMg[CO 3 ] 2 ) because gypsum (CaSO 4 · 2H 2 O) and halite (NaCl) are too soluble
and are quickly removed. In the tropics and subtropics,
limestones (called carbonates to refer to all the common
limestone and dolostone types) are being deposited today
and tens of thousands of kilometers of coastline at low latitudes consist of these deposits (Wilson, 2012). At higher
latitudes, older limestones are often present on the coast
for long distances, such as along the Adriatic Sea. The soluble nature of limestones means they can dissolve to form
a myriad of landforms collectively named karst: caves,
springs, sinkholes, sinking streams, and unusual rock
sculpture called karren (e.g., Ford and Williams, 2007;
Palmer, 2007). The coastal environment creates a novel
karst setting resulting from the outflow of fresh groundwater of the freshwater lens and the land mixing with salt
water invading from the sea (Figure 1a) (Scheffers et al.,
2012). The mixing of these two waters, even if both are
initially saturated with CaCO 3 , results in brackish water
that is capable of additional dissolution (Figure 1b). The
dissolution of limestone bedrock in the coastal mixing
zone is accelerated compared to that done in continental
interiors. The signature landform of the carbonate coastal
environment is the flank margin cave, so named for its
development by mixing dissolution in the discharging
margin of the freshwater lens, under the flank of the
enclosing landmass (Mylroie and Carew, 1990). Flank
margin caves are part of the Carbonate Island Karst
Model, or CIKM (Mylroie and Mylroie, 2007), developed
to explain the various karst processes and phenomena that
occur in carbonate coasts. Carbonate coasts develop
a unique type of karren influenced by the youthfulness
of the rock, boring and grazing by organisms, wave action,
and mixing of sea and fresh waters; see Taboroši and
Kázmér (2013) for a full and complete review of coastal
karren.
Flank margin caves range in size from voids only a few
meters across to extensive systems with 20 km of linear
survey (Figure 2). They form very rapidly, and on many
carbonate coasts fossil caves above modern sea level, with
M.J. Kennish (ed.), Encyclopedia of Estuaries, DOI 10.1007/978-94-017-8801-4,
© Springer Science+Business Media Dordrecht 2016