Karst topography

Wiki Write-Off Entry
Student Chapter	Universitas Diponegoro
Competition	June 2015

Karst environment

Karst is terrain in which soluble rocks are altered above and below ground by the dissolving action of water and that bears distinctive characteristics of relief and drainage. Karst has unique hydrology condition, this condition is caused of karst composed of soluble lithology and the lithology has good condition in secondary porosity.

Karst has a unique characteristic, usually in the area which as karst landform comprising a lot of cavity in surface, and the famous characteristic is the type of river, that is multibasinal river, and in karst usually has cave in subsurface.

Karst not only occurs in areas comprising dominant carbonate rock, but it can also occur in areas comprising not dominant carbonate rock but soluble rock.

Karst classification

Karst topography has found in many places in the world with a lot of type, and all types of karst are classified into three classification :

• Cvijic: based on development
• Gevozdeckij: based on morphology
• Sweeting: based on climate

Cvijic classification

Cvijic divides karst topography into three groups:

• Holokarst: Complete karst develops in areas included entirely of soluble carbonate rock. It is characterized by the vast, bare, and rocky land, without arable land and with or without the presence of veregetation.
• Merokarst: Incomplete karst with many properties of nonkarst regions. The karst phenomena in these regions are in frequent and karstifiction occurs in lower depths. Carbonate sediments are covered with arable soil and with vegetation. Merokarst usually too called as covered karst.
• Transitional: The degree of karstification is between holokarst and merokarst. The transitional type is usually formed in limestone isolated by impermeable and less soluble sediments.

Gevozdeckij classification

Gevozdeckij classification divides karst into bare karst, covered karst, soddy karst, buried karst, tropical karst, and permafrost karst.

Bare karst is similar to holokarst.

Covered karst occurs if carbonate rocks are covered by alluvium deposit.

Soddy karst or soil covered karst is karst that develops in limestone covered by soil or terra that produced by limestone dissolution.

Buried karst is karst covered by other rocks so the morphology is unidentified and only can identified by drill data.

Tropical karst or cone karst only occurs in tropical areas, while permafrost karst only occurs in snowy climates.

Sweeting classification

Sweeting classified karst as true karst, fluviokarst, glaciokarst, tropical, arid and semiarid karst; this classification is based on climate. True karst is perfect karst and called as holokarst, true karst should as doline karst that caused of vertical dissolution. All karst that is not doline is classed as deviant; one example of true karst is dinaric karst.

Fluviokarst is formed by combination between fluvial process and dissolution process, fluviokarst usually occur in areas that consist of limestone passed by allogenic rivers.

Glaciokarst is formed when karstification is affected by glacial processes, and usually occurs in areas with limestone.

Nival karst is formed by the karstification in glacial and periglacial environments.

Tropical karst occurs in warm climates, this type caused by great precipitation and evaporation.

Kegelkarst is characterized by accumulation of continue domes, space between one dome to another dome make basin and the basin is look like star and mentioned as cockpit.

Karst topography

Karst topography is divided into macro topography and micro topography. Von Engeln defined the conditions supporting formation of topography karst:

• Soluble and near surface
• Massif, thick, and buried
• Medium to high accumulation rainfall
• Surrounded by valley

Micro topography

Lapies is an uneven shape in limestone surface caused by dissolution or other processes.

Karst split is dissolution space formed in surface, karst split actually developed from karst runnel; if there are a large number of karst runnels and intersections, they will form a karst split.

Speleothem is an ornament found in karst cave; they are commonly stalactite hanging in the roof of the cave and stalagmites at the bottom of the cave.

Fitokarst is an undulating surface, with interconnected vent holes.

Macro topography

Dolina is the result of condensation of depression covered with diameters ranging from a few meters to several kilometers, its depth reaches hundreds of meters to several kilometers, its depth reaches hundreds of meters and a round or oval shape.

Uvala is a topography that is formed when an adjacent Surupan Surupan develop so interconnected and form a large depression in the ground floor is bumpy.

Polje according cvijic 1985 is a karst landform elements that have a basin wide, flat base, drainage krastik, elongated shape parallel to local structures, basic Polje have tertiary rock layers.

Karst window according Twidale 1976 was a hole in the roof of the cave that connects the chamber with the air outside the cave formed by the roof of the cave collapsed. karst valleys are large valleys or grooves contained in karst land. This valley is formed by the flow of surface water that eroded the rocks in its path.

Cave is underground rooms that can be reached from the surface and large enough when entered by a human

Tunnels and bridges nature according to Von Engeln 1942 an underground passageway formed by leaching and erosion by the flow of groundwater or underground Form the rest of dissolution

Cone karst is cone-shaped karst hills, steep slopes and surrounded by a depression which is usually referred to as a star. Cone karst often referred to as kegel karst.

Tower karst according to Ritter in 1978 the tower karst is the rest of dissolution and erosion of the hill-shaped tower with a steep slope, upright or hanging, separated from one another and surrounded by alluvial plains.

Mogote is a steep hill which is the residual leaching and erosion, generally surrounded by alluvial plains were nearly flat (flat).

Karstification

Kartsification or formation process of karst morphology dominated by dissolves process. Limestone dissolve process begins with CO₂ that dissolved in water and form H₂CO₃. Dissolve H₂CO₃ is unstable and dissolve become H^- and HCO₃^2-. These H- ions furthermore dissolve CaCO₃ become Ca²⁺ and HCO₃^2-

${\text{CaCO}}_{3}+{\text{H}}_{2}{\text{O}}+{\text{CO}}_{2}\to {\text{Ca}}^{2+}+{\text{HCO}}_{3}^{2-}$

Karstification Factors

Karstification is influenced by two main factors: control and simulation. Control factors determine whether karstification can develop or not and simulation factors determine velocity and completeness of the karstification proces.s

Figure 1 Limestone dissolution

Control factors

1. Dissolvable rock, compact, thick, and have many fissures
2. Enough rainfall (>250 mm/year)
3. Exposed rock on elevated that possible develop water circulation or vertical drainage

Simulation Factor

1. Temperature
2. Closing forest

Rock that is composed of high CaCO3 is dissolvable. At higher than CaCO3 composition, karst morphology will develop. The compaction of rock determines the stability of karst morphology after dissolution. If rock is soft, then every visible karst will vanish quickly because of the dissolution processor erosion and mass flow, therefore karst visibility can't develop. Thickness determines the form of vertical water circulation more, without thick layer, vertical water circulation that is requirements of karstification can ongoing. Without vertical circulation, process that ongoing is lateral flow like on surface rivers and close basins can’t form. Rock fissures are way to enter water formed vertical drainage and developing Sub-surface River and concentrate dissolution

Rainfall is the main cause of dissolution of karstification. Higher rainfall, higher dissolution, until the level of dissolution that occurs in limestone becomes higher. Elevation of limestone in exposed in surfaces determines vertical circulation and drainage.

Although limestone has a thick layer exposed several meters from sea level, karstification will never occur. Vertical drainage will occur when the distance between surface of limestone and water surface or basement of limestone is bigger. The higher the exposed limestone surface, the greater the distance between surface of limestone with water surface and better vertical water circulation, and also more intense karstification process.

Figure 2 Connection between CO2 concentrations with dissolution capacity toward limestone

Temperature drives karstification process is the primary connection with organism activity. Place with warm temperature such as in tropical area is an ideal place for organism that produce CO2 in ground. Temperature determines evaporation, higher temperatures will impact higher evaporation and as a result there will be recrystallization of carbonate solution in surface and near surface. This recrystallization will make amplification surface (case hardening) with the result that karst morphology that form can hold out for denudation process (erosion and mass flow).

The velocity of reaction so true as bigger in low temperature, because concentration of CO2 is higher than in low temperature. But dissolution level in tropical area is high because availability fall of rain that more abundant and higher organism activity. Closing forest is also simulator factor in developing because dense forest will have abundant CO2 in the ground as a result by reorganizing organic residues by microorganism. Higher CO2 concentrate in water will impact higher dissolution water level toward limestone. CO2 in atmosphere isn’t significantly having variation, as a result variation process of karstification depends on CO2 from organism activity.

Connection between CO2 concentrations with dissolution capacity toward limestone show in Figure 2 and Diagram 1.

Diagram 1 Karstification factors and influence in dissolution process

Karst Aquifers

Figure 3 Conduit flow system and Diffuse flow system

Karst aquifers can describe as a geological formation that could store and flow ground water in moderate count in certain gradient. So it means that karst formation could call as aquifers. Karst aquifers are characterized by a network of conduits and caves the conduits and caves drain the pore space between the limestone grains (intergranular or primary porosity) and the fractures (secondary porosity) formed by joints, bedding planes, and faults.

To study about karst aquifers system there are some method that should do such as geologic method, speleology, hydrologic methods, hydraulic methods, isotopics methods, tracer test, geophysical test, and modeling.

Hydrology system of karst aquifers

Figure 4 Diffuse, mixed and conduit karst groundwater

In karst topography, there are three component of water recharge area that is from karst formation itself, non-karst area and entrance water from above karst formation. Karst formation have three groundwater systems and between them have connection. At the beginning water enter from the fissure and in this phase diffuse system is dominated and then when solution process developed it will make a result a conduit system and impact increasing count of flow. In this phase call mixed groundwater system. And the system will be developed until conduit system is dominated and it is occur on mature phase of karst.

White derived karst aquifers into three conceptual models:

• Diffuse-flow karst aquifers are dominated by diffuse system and low dissolution activity, usually occurring in unsolvable limestone such as dolomite.
• Free flow karst aquifers occur on a mixed flow system; in this model groundwater controlled by distribution and direction from each path,
• Confined-flow karst aquifers usually occur beneath rocks that have low permeability and very controlled by layer above the aquifers.

Other sources

• Hugget, R. J., 2007, Fundamentals of geomorphology, 2nd ed.: New York, Routledge.
• Haryono, E., and N. A. Tjahyono, 2012, Geomorfologi dan Hidrologi Karst: Jakarta, UGM Press.
• Karamouz,M., A. Ahmadi, and M. Akhbari, 2012, Groundwater hydrology: Engineering, planning, and management: Jakarta, UGM Press.
• Geomorphology Lab Assistant Team, 2014: Buku Panduan Praktikum Geomorfologi dan Geologi Foto: Semarang, Universitas Diponegoro.