Visit Mount Gambier
About Mount Gambier - Geology
Thirty million years ago, our land was covered with a warm shallow ocean. The remains of fish bones, shells and fossils fell to the ocean floor, forming a huge wedge of limestone which now underlies the entire region - thus the name 'The Limestone Coast'
Moving slowly southwards towards the ocean through the limestone and its arterial system of caves and crevices the water is plentiful and contributes to the beauty of the city's parks and gardens and to the rural sector.
Limestone, formed millions of years ago in a totally marine environment and made up of fossils and corals, extends from the Bordertown area down to the coast at Port MacDonnell where it is more than 300 metres thick.
Rainfall soaks down through the surface into the limestone which acts like a huge sponge. Called the unconfined aquifer, the ground water gradually moves southwards underground finally discharging to the ocean at various points along the coast between Port MacDonnell and the Victorian border.This abundance of "groundwater" contibutes greatly to the beauty of the citys parks and gardens and to the rural sector.
Mount Gambier's famous Blue Lake, Little Blue Lake, Ewens Ponds and Piccininnie Ponds are just a few of the locations which provide a "window" into this underground water system.
The abundance of water in the Mount Gambier area provides a wonderful array of food, wine and natural experiences. Rural industries draw underground water from bores sunk at various depths into the limestone creating not only a richness of colour but also significant monetary value to the region.
Limestone is an important product to industry. It is a major building stone for domestic and industrial buildings and is used extensively for road construction. Other significant uses include agricultural lime, glass and fibre-glass, sculpture and calcium based products such as tablets, toothpaste and talcum powder.
Engelbrecht Cave, a huge complex of limestone caves under the city of Mount Gambier offers tours into two of the chambers where cave divers enter the water to dive under the city. View the underground water as it slowly filters through to the Blue Lake, on to sinkholes south of Mount Gambier then out to the ocean – see Unique Attractions.
Umpherston Sinkhole was originally a cave formed by the dissolution of limestone. The sinkhole was formed when the top of the cave, fell to the cave floor creating terraces and the prefect environment for its beautiful sunken garden. On dusk, the cave comes to life when possums come out to feed in the floodlit gardens.
Surrounded by a beautiful rose garden, the Cave Garden was the original water supply for early settlers in Mount Gambier. Viewing platforms suspended above the cave provide awesome views of the limestone cave which directs storm water run-off from the streets down under the city into the underground water system. Some of the history of Mount Gambier has been captured in the beautiful architecture of the city much of which has been created from the natural limestone and dolomite rock.
Masses of exposed limestone can be seen in the area near Little Blue Lake. Known as Karst, this exposed limestone is gradually being selectively dissolved to produce indentations in the surface.
The limestone is also gradually dissolving beneath the surface, sometimes forming cavities, some known by cave divers to be as large as the MCG. Others run horizontally, following fault lines which have been created over millions of years. The most complex of these explored by only the most experienced divers, is Tank Cave, which provides 7 kms of water filled caverns with only one entrance.
Little Blue Lake just 15 minutes drive south of Mount Gambier was once a cave. Now that the top has collapsed to the bottom of the cave, the crystal clear water of this sinkhole is exposed, providing a popular but cool swimming hole for the experienced swimmer. Underground water from this same system emerges from the bottom of Ewens Ponds, bubbling upwards then flowing through the three ponds, down Eight Mile Creek to the ocean, providing a popular snorkel and diving site.
Piccaninnie Ponds an 85 metre deep water-filled limestone cave can be snorkelled and dived under permit.
Mount Schank was formed when volcanic pressure exploded from deep within a limestone joint, a walk to the summit of the extinct crater of Mount Schank at 158 metres above sea level, provides wonderful views of the surrounding countryside.
The beautiful Glenelg River exposes white limestone cliffs as it meanders through the Lower Glenelg National Park. River cruises regularly depart from Nelson, most stopping up river for those wishing to discover the wonders of the natural limestone cave formations in Princess Margaret Rose Caves or the natural beauty of the walking trail leading to spectacular views of the Glenelg River Gorge.
Tantanoola Cave has been formed in the cliff face of what was an ancient coastline. Through possible volcanic influence the limestone has changed to dolomite, a unique feature of this cave which displays a spectacular array of decorations in its large single chamber.
Little more than an hour to the north of Mount Gambier is Naracoorte Caves. The 307 ha Park is World Heritage listed and contains 19 known fossil deposits. Many caves along the ridge have had openings that have acted as pitfall traps, preserving a record of animal life of the last 500,000 years.
Just 35 minutes north of Mount Gambier is Coonawarra, where the prized red terra rossa soil over the free draining limestone and the abundance of irrigation water underground in the lower levels of the limestone allows great flexibility in the management of the vines to produce the famous Coonawarra Wine. Within the 12 km strip, the 22 wineries open for cellar door sales. Most are gate after gate along the highway, offering a wide selection for the wine connoisseur.
Along the extent of coastline from Kingston to the Victorian border the scenic splendour of the rough weathered limestone cliffs contrasts with smooth white sandy beaches. Much of the coastline is accessible via the 4WD tracks of the coastal parks which offer bush camping with basic facilities.
During winters of high rainfall, surplus water seeps down through the limestone recharging the underground water system.
Making its way gradually to the ocean, the underground water has contributed to the dissolution of the limestone forming many caves beneath the City of Mount Gambier and surrounding areas. The Blue Lake was formed when the volcano erupted through the limestone allowing the underground water to fill the crater, creating the lake that we see today.
Visit Mount Gambier to appreciate the many natural attractions that are associated with this unique and mysterious landscape.
However, the natural colour of the water is blue, and for the same reason teh sky is blue. Therefore, the Blue Lake (and all lakes) should be blue. The question to answer therefore: Why does the Blue Lake become less blue in winter?
Within the lava areas are four main precincts all with varying landscapes according to the period and type of eruption, including Australias youngest volcanoes, highly accessible volcanic cave systems, off-shore volcanic islands, remains of coastal volcanoes and extensive systems of craters, lakes and wetland.
Volcanic activity occurred in the Mount Gambier area in recent geological time and has been recorded as an important part of local Aboriginal culture. The outbursts, which would have been spectacular, took place during 2 different eruptive phases, along the edge of a main zone of activity centred on southern and western Victoria.
Mount Gambier and Mount Schank, the more recent eruptions, are two of the better preserved examples of their type in Australia and are well known scenic attractions. Less well known, is the extent of volcanic activity in the Mount Burr complex which contains 15 eruptive centres dated as occurring from 10,000 to 2 million years ago. Lakes Leake and Edward are water bodies present within volcanic craters, relying on rainfall to recharge them each year.
The area is popular with naturalists, geologists, tourists and locals as the volcanic features are easily accessible via the walking trails provided. Lava bombs, some containing olivine crystals have been found in the Mount Gambier lakes area.
Engelbrecht Cave, a large complex of caves under the City of Mount Gambier provides good examples of the processes involved in cave formation. A fascinating tour of Engelbrecht Cave includes entry into two large chambers which expose the underground water table. These two chambers lead off into other water filled caves which can only be accessed by trained and experienced divers.
Once a cave has been formed in the limestone and the water level drops, leaving the cave dry, the continuing slow process of water dripping from the ceiling sometimes forms stalactites and stalagmites. Small droplets of water can hang from the ceiling for up to 10 hours, and as the carbon dioxide is given off, minute deposits of calcite are left on the cave ceiling and floor, building up over a period of time to form the elaborate decorations as seen in some of the caves in the area.
Tantanoola Cave – a beautiful single chamber dolomite cave created in an ancient stranded sea cliff.
Princess Margaret Rose Cave – a unique tunnel cave of sculptured limestone and comprehensive decoration, it was formed approx 500,000 years ago by an underground stream deep within the cliffs of the Glenelg River Gorge.
Naracoorte Caves – a complex of caves formed within the ridge of what was once a stranded dune system.
In the case of a dry cave, the topsoil which was above the cave, ends up on the floor of the cave creating the perfect environment for a sunken garden. This is the case with both Umpherston Sinkhole and the cave at Cave Garden.
There are numerous water filled caves and sinkholes in the Mount Gambier area that can be accessed for diving or snorkelling. However, most are situated on private land and are accessible only by permission of the landowner and within the regulations and training criteria as set by the Cave Diving Association of Australia (CDAA).
Due to the constant cold temperature of the water in all caves and sinkholes, warm, well insulated full length wetsuits should always be worn. Divers and snorkellers may enter Ewens Ponds. Guidelines are available from "The Lady Nelson" Visitor Centre and The Department for Environment, Heritage & Aboriginal Affairs.
To protect the unique and fragile environment of Piccaninnie Ponds and to improve the diving and snorkelling experience, a permit and time slot system is operated by The Department for Environment, Heritage & Heritage which requires the completion of an indemnity and conditions form and payment of relevant fees.
Annual Diver Permit $65.00, Single Slot Dive Permit $30.00, Single Slot Snorkel Permit $10.00, Single Slot Snorkel Concession $8.00
Mount Gambier - Heart of the Limestone Coast
The lushness of the Mount Gambier area is not only due to its annual rainfall. Its life blood, is the abundance of underground water which lies in the wedge shaped block of limestone beneath the earth's surface.Moving slowly southwards towards the ocean through the limestone and its arterial system of caves and crevices the water is plentiful and contributes to the beauty of the city's parks and gardens and to the rural sector.
Limestone, formed millions of years ago in a totally marine environment and made up of fossils and corals, extends from the Bordertown area down to the coast at Port MacDonnell where it is more than 300 metres thick.
Rainfall soaks down through the surface into the limestone which acts like a huge sponge. Called the unconfined aquifer, the ground water gradually moves southwards underground finally discharging to the ocean at various points along the coast between Port MacDonnell and the Victorian border.This abundance of "groundwater" contibutes greatly to the beauty of the citys parks and gardens and to the rural sector.
Mount Gambier's famous Blue Lake, Little Blue Lake, Ewens Ponds and Piccininnie Ponds are just a few of the locations which provide a "window" into this underground water system.
The Limestone Connection
Creeks from both Ewens Ponds and Piccininnie Ponds carry millions of litres of water an hour to the ocean. Just down the beach from Piccininnie Ponds, water can be seen bubbling up through the sandy beach.The abundance of water in the Mount Gambier area provides a wonderful array of food, wine and natural experiences. Rural industries draw underground water from bores sunk at various depths into the limestone creating not only a richness of colour but also significant monetary value to the region.
Limestone is an important product to industry. It is a major building stone for domestic and industrial buildings and is used extensively for road construction. Other significant uses include agricultural lime, glass and fibre-glass, sculpture and calcium based products such as tablets, toothpaste and talcum powder.
Engelbrecht Cave, a huge complex of limestone caves under the city of Mount Gambier offers tours into two of the chambers where cave divers enter the water to dive under the city. View the underground water as it slowly filters through to the Blue Lake, on to sinkholes south of Mount Gambier then out to the ocean – see Unique Attractions.
Umpherston Sinkhole was originally a cave formed by the dissolution of limestone. The sinkhole was formed when the top of the cave, fell to the cave floor creating terraces and the prefect environment for its beautiful sunken garden. On dusk, the cave comes to life when possums come out to feed in the floodlit gardens.
Surrounded by a beautiful rose garden, the Cave Garden was the original water supply for early settlers in Mount Gambier. Viewing platforms suspended above the cave provide awesome views of the limestone cave which directs storm water run-off from the streets down under the city into the underground water system. Some of the history of Mount Gambier has been captured in the beautiful architecture of the city much of which has been created from the natural limestone and dolomite rock.
Masses of exposed limestone can be seen in the area near Little Blue Lake. Known as Karst, this exposed limestone is gradually being selectively dissolved to produce indentations in the surface.
The limestone is also gradually dissolving beneath the surface, sometimes forming cavities, some known by cave divers to be as large as the MCG. Others run horizontally, following fault lines which have been created over millions of years. The most complex of these explored by only the most experienced divers, is Tank Cave, which provides 7 kms of water filled caverns with only one entrance.
Little Blue Lake just 15 minutes drive south of Mount Gambier was once a cave. Now that the top has collapsed to the bottom of the cave, the crystal clear water of this sinkhole is exposed, providing a popular but cool swimming hole for the experienced swimmer. Underground water from this same system emerges from the bottom of Ewens Ponds, bubbling upwards then flowing through the three ponds, down Eight Mile Creek to the ocean, providing a popular snorkel and diving site.
Piccaninnie Ponds an 85 metre deep water-filled limestone cave can be snorkelled and dived under permit.
Mount Schank was formed when volcanic pressure exploded from deep within a limestone joint, a walk to the summit of the extinct crater of Mount Schank at 158 metres above sea level, provides wonderful views of the surrounding countryside.
The beautiful Glenelg River exposes white limestone cliffs as it meanders through the Lower Glenelg National Park. River cruises regularly depart from Nelson, most stopping up river for those wishing to discover the wonders of the natural limestone cave formations in Princess Margaret Rose Caves or the natural beauty of the walking trail leading to spectacular views of the Glenelg River Gorge.
Tantanoola Cave has been formed in the cliff face of what was an ancient coastline. Through possible volcanic influence the limestone has changed to dolomite, a unique feature of this cave which displays a spectacular array of decorations in its large single chamber.
Little more than an hour to the north of Mount Gambier is Naracoorte Caves. The 307 ha Park is World Heritage listed and contains 19 known fossil deposits. Many caves along the ridge have had openings that have acted as pitfall traps, preserving a record of animal life of the last 500,000 years.
Just 35 minutes north of Mount Gambier is Coonawarra, where the prized red terra rossa soil over the free draining limestone and the abundance of irrigation water underground in the lower levels of the limestone allows great flexibility in the management of the vines to produce the famous Coonawarra Wine. Within the 12 km strip, the 22 wineries open for cellar door sales. Most are gate after gate along the highway, offering a wide selection for the wine connoisseur.
Along the extent of coastline from Kingston to the Victorian border the scenic splendour of the rough weathered limestone cliffs contrasts with smooth white sandy beaches. Much of the coastline is accessible via the 4WD tracks of the coastal parks which offer bush camping with basic facilities.
The Blue Lake
Mount Gambier's Blue Lake , situated in a volcanic crater, exposes crystal clear water that has filtered underground as it passes slowly under the city through the limestone. Each year in November the lake starts its colour change from winter sombre blue to brilliant turquoise blue, before returning to its winter hue in March.During winters of high rainfall, surplus water seeps down through the limestone recharging the underground water system.
Making its way gradually to the ocean, the underground water has contributed to the dissolution of the limestone forming many caves beneath the City of Mount Gambier and surrounding areas. The Blue Lake was formed when the volcano erupted through the limestone allowing the underground water to fill the crater, creating the lake that we see today.
Visit Mount Gambier to appreciate the many natural attractions that are associated with this unique and mysterious landscape.
Colour Change Theory
Mount Gambiers Blue Lake is unique. There are lots of blue lakes in the world, but no other lake changes colour so dramatically every year. The mystery behind the transformation from brilliant turquoise blue in summer to steel-grey in winter, has only been identified in the last ten years.Why is the Blue Lake blue?
Is it blue dye? A bunyip? A range of explanations have been proposed over the last century. It was also proposed that the blue colour was caused by flouresence of dissolved organic matter whcih builds up seasonally in the upper layers of the lake. Another theory was that the blue colour was caused by absorption of all incident visible radiation except blue by finely crystaline calcite in the surface of the lake.However, the natural colour of the water is blue, and for the same reason teh sky is blue. Therefore, the Blue Lake (and all lakes) should be blue. The question to answer therefore: Why does the Blue Lake become less blue in winter?
Winter - August
In winter the lake is green-grey. It is thoroughly stirred up with dead algae which are mixed into the top of the lake at its lowest. The lake appears less blue due to absorption of blue light by humic substances in the near- surface water. Low rates of calcite precipitation are insufficient to remove the humic substances from the water column hence the water clarity is poor.Autumn - May
As the top layer of water cools in autumn the calcite production slows dramatically but the mass flux of organic material continues. The concentrations of algae in the near surface water increases and the colour returns to aqua. New and old humic substances are mixed into the surface water from below, which is the probable casue of the colour change. The addition of humic substances to th e water increases the absorbency of light in the blue end of the spectrum.Spring - November
The lake commences stratification in spring forming a thin layer of warm water which cuts off deep circulation in the lake. Degassing of CO2 modifies the pH of the surface water promoting precipitation of calcite. An abundance of white calcite forms near the surfaceof the lake, making the water appear brighter blue. The calcite comes from the groundwater inflow from the adjacent limestone and dolomite aquifer. The high rates of calcite production removes the humic acids from the water column. The spring colour change results principally from the introduction of significant quantities of fine crystalline calcite.Summer - February
In summer, the calcite continues to form. The calcite continues to strip the humic substances (which come mostly from dead algae in the lake) from the water (through a chemical reaction) in the top of the lake, and the calcite and humic substances settle to the bottom of the lake. As more and more humic substances are removed through the summer, the lake becomes deeper and deeper blue. (The humis substances being produced by algae deeper in the lake dont get into the water near the top of the lake because the lake stratification in summer prevents mixing of the two water layers.)Is the Blue Lake blue?
Sunlight enters the lake, and a small proportion comes back out again. The proportion, and colour, of the light that comes back out is controlled by processes called scattering and absorption. In summer, the light coming out of the lake contains a range of colours, but the dominant colour is blue. In winter there is far less (and when looked at in detail it contains more green colour.Yes - the Blue Lake is blue
The amount of colour and light coming in and out if the Blue Lake in summer and winter .Scattering of light in water
Water, gases and small particles (ie less than 0.0000005m) diameter scatter light in all directions due to density fluctuation scattering. Blue light is scattered more strongly than red light, and therefore more blue light is backscattered toward the surface of the lake than red light. Particles much larger than the wavelength of light (>0.000005m) scatter light in the forward direction.Absorption of Light in Water
It is absorption that plays the major role in affecting the colour of the emergent light. All light absorption that takes place in water is attributable to 4 components. Water absorbs only weakly in the blue and green spectrum but is significant in the red end. Soluble humic substances (eg tannins) stronlgy absorb blue light. Particulate matter does not absorb light strongly . Algae absorbs blue and red.Volcanoes in the Mount Gambier Area
Located in Southern Australia on the plains of Victoria's Western district and South Australia's South East (Limestone Coast) is Australias most extensive volcanic province, recognized as being the sixth most significant and the third largest in the world, encompassing more than fifty six sites.Within the lava areas are four main precincts all with varying landscapes according to the period and type of eruption, including Australias youngest volcanoes, highly accessible volcanic cave systems, off-shore volcanic islands, remains of coastal volcanoes and extensive systems of craters, lakes and wetland.
Volcanic activity occurred in the Mount Gambier area in recent geological time and has been recorded as an important part of local Aboriginal culture. The outbursts, which would have been spectacular, took place during 2 different eruptive phases, along the edge of a main zone of activity centred on southern and western Victoria.
Mount Gambier and Mount Schank, the more recent eruptions, are two of the better preserved examples of their type in Australia and are well known scenic attractions. Less well known, is the extent of volcanic activity in the Mount Burr complex which contains 15 eruptive centres dated as occurring from 10,000 to 2 million years ago. Lakes Leake and Edward are water bodies present within volcanic craters, relying on rainfall to recharge them each year.
The area is popular with naturalists, geologists, tourists and locals as the volcanic features are easily accessible via the walking trails provided. Lava bombs, some containing olivine crystals have been found in the Mount Gambier lakes area.
Caves & Sinkholes
From Caves
As rain water passes through the atmosphere, it absorbs carbon dioxide and becomes mildly acidic. Limestone, when saturated under water, is slowly dissolved by the acidic solution causing cracks and fissures which gradually enlarge into caves. There are many fine examples of caves throughout the South East, some of which are now dry, others far reaching below the water table and are therefore water filled caves.Engelbrecht Cave, a large complex of caves under the City of Mount Gambier provides good examples of the processes involved in cave formation. A fascinating tour of Engelbrecht Cave includes entry into two large chambers which expose the underground water table. These two chambers lead off into other water filled caves which can only be accessed by trained and experienced divers.
Once a cave has been formed in the limestone and the water level drops, leaving the cave dry, the continuing slow process of water dripping from the ceiling sometimes forms stalactites and stalagmites. Small droplets of water can hang from the ceiling for up to 10 hours, and as the carbon dioxide is given off, minute deposits of calcite are left on the cave ceiling and floor, building up over a period of time to form the elaborate decorations as seen in some of the caves in the area.
Tantanoola Cave – a beautiful single chamber dolomite cave created in an ancient stranded sea cliff.
Princess Margaret Rose Cave – a unique tunnel cave of sculptured limestone and comprehensive decoration, it was formed approx 500,000 years ago by an underground stream deep within the cliffs of the Glenelg River Gorge.
Naracoorte Caves – a complex of caves formed within the ridge of what was once a stranded dune system.
To Sinkholes
Sinkholes are formed when the roof of a cave weakens and collapses in or falls to the bottom of the cave, leaving an opening at ground level and providing a natural window into the underground cave or water system.In the case of a dry cave, the topsoil which was above the cave, ends up on the floor of the cave creating the perfect environment for a sunken garden. This is the case with both Umpherston Sinkhole and the cave at Cave Garden.
Diving and Snorkelling
There are numerous water filled caves and sinkholes in the Mount Gambier area that can be accessed for diving or snorkelling. However, most are situated on private land and are accessible only by permission of the landowner and within the regulations and training criteria as set by the Cave Diving Association of Australia (CDAA).
Due to the constant cold temperature of the water in all caves and sinkholes, warm, well insulated full length wetsuits should always be worn. Divers and snorkellers may enter Ewens Ponds. Guidelines are available from "The Lady Nelson" Visitor Centre and The Department for Environment, Heritage & Aboriginal Affairs.
To protect the unique and fragile environment of Piccaninnie Ponds and to improve the diving and snorkelling experience, a permit and time slot system is operated by The Department for Environment, Heritage & Heritage which requires the completion of an indemnity and conditions form and payment of relevant fees.
Annual Diver Permit $65.00, Single Slot Dive Permit $30.00, Single Slot Snorkel Permit $10.00, Single Slot Snorkel Concession $8.00