FACT SHEET Karst Systems Geology What is a Karst System? A Karst system is a landscape whose features are affected by soluble rocks under the ground. Soluble rocks can be dissolved or broken apart by water. Rocks like limestone are soluble. Over time, holes created in the rock enlarge to eventually form an underground drainage system. Karst science – how the rock dissolves. Carbon dioxide (in the air) plus water forms carbonic acid. Carbonic acid can dissolve limestone (calcium carbonate).
They are formed when the calcium carbonate dissolved in water comes back out. It takes thousands of years to make a large calcium carbonate formation, drip by drip. The average growth rate of a stalactite or stalagmite is 0.13mm per year with the fastest rate being only 3mm per year. Farming risks Farming in a Karst area has some risks. Sinkholes can appear quickly and ‘swallow’ machinery, animals or even farm houses. Water can disappear underground rather than flowing through rivers. Wells dug in Karst areas can become polluted.
Sinkholes can appear in farming areas Photo source: Martin Finzel
Pollution Karst areas can be polluted easily. This is because the holes in the ground (like vertical shafts or sinkholes) allow water to run quickly underground. The natural filtration system is missing. A Karst system cave Photo source: Raelee Turner
On the surface and below Karst land can have a number of signs from the rock dissolving. This includes ‘flutes’ and ‘runners’ which are small features on the land surface. Larger features include vertical shafts or sinkholes that travel from the surface to underground. The largest feature of a Karst system is a cave. Limestone Caves The most well known features of a Karst System are limestone caves. These caves are characterised by caverns, ‘stalactites and stalagmites’. Caverns can be small holes, or large enough to drive through. Large caverns are sometimes opened for tourists because of their amazing and interesting features. Stalactites and stalagmites are incredible.
If there is pollution like cow manure on the surface, it can travel underground still full of manure. Wells dug for people or animals can contain this pollution. Pollution can also travel rapidly from one area to another through underground streams. These streams can then reappear on the surface in wetlands or streams. This is a very quick way to spread pollution.
FACT SHEET Karst Systems Geology Potential study options include: • Hydrology (water) • Biology (plants and animals) • Geology (rock formation and shaping) • Tourism (how to attract tourists sustainably) • Natural Resource Management Further information Department of Primary Industries, Parks, Water and Environment www.dpiw.tas.gov.au Follow the links - Managing Our Natural Resources > Geoconservation > Karst Managing Our Natural Resources > Geoconservation > Groundwater Dependent Ecosystems
Limestone caves can form under Karst landscapes Photo source: Raelee Turner
State of the Environment Tasmania http://soer.justice.tas.gov.au/2003/copy/55/index. php
Biology There are a number of plants that live in Karst systems. Some trees, including tea-trees sink their roots into the ground and suck up Karst System water. Wetland and river plants and animals may receive water from Karst Systems.
Wikipedia www.en.wikipedia.org (search: Karst, Stalactite, Stalagmite)
There are many unique and interesting animals living in caves. These include roundworms, flatworms, nemertine worms, segmented worms, water mites, molluscs, insects (caddisflies, mayflies stoneflies) and crustaceans (copepods, ostracods, syncarids, isopods, amphipods and decapods.)
Cradle Coast NRM www.cradlecoastnrm.com
North West Tasmania Karst Systems Geology North West Tasmania has a number of high geoconservation significance features in Karst Systems. This includes: • Large sea caves • The Mole Creek Caves • Spring mounds with ‘giant marsupial’ fossils • Desert dune systems • Coastal fossils and high sea cliffs Threats to Karst Systems include: • Pollution • Development • Farming Are you interested in the future of Karst Systems? Karst Systems are still not well understood. There are opportunities for careers in research about Karst Systems. Karst systems also generate tourism which you could be involved in.
Mole Creek Caving Club www.mole.org.au