Mount Schank State Heritage Area

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Location

The volcanic cinder cone of Mount Schank is a striking landscape feature 12.5 kilometres south of Mount Gambier, along the Port MacDonnell Road. This characteristically shaped cone has been little modified by erosion and rises approximately 100 metres above the flat coastal plain.

The Mount Schank State Heritage Area, of approximately 150 ha, encompasses three separated areas of land around, and adjacent to, the volcano. The largest area includes Mount Schank, which slightly overlaps a smaller, earlier cone on its southern side. An extension of the original volcanic fissure (with a small line of scoria cones) is protected to the north, while land within a 50-metre radius of a blowhole on the eastern side is also included as part of the State Heritage Area.

View Public Notice (250Kb PDF).

Significance

The Mount Schank State Heritage Area, declared on 11 June 1992, recognises the significance of this cone-shaped landform, which is a rare and relatively undisturbed South Australian example of volcanic activity in recent geological time.

Distant view of Mount Schank from Centenary Tower

Together with nearby Mount Gambier, Mount Schank represents the most recent volcanic eruptions in south-eastern Australia. Scientific assessments indicate that Mount Schank is slightly older.

Unlike Mount Gambier however, Mount Schank has not been obscured by urban development. Farming and some quarrying have taken place in the area and on its flanks, but the unmistakable cone shape has not been impaired. Similarly, important geological features have remained intact and largely unaffected, which makes this area an important site for teaching about, and continuing scientific research into, volcanic activity in Australia.

Mount Schank is a designated South Australian Geological Monument.

Geology

The features seen at Mount Schank today are the result of two phases of volcanic activity. The first stage developed a significant scoria cone with an ash ring (maar) to the south and a basaltic lava flow to the west. The later phase created the main cone, which buried the original scoria cone and overlapped the maar. Work by the University of Adelaide Physics Department has dated the original Mount Schank eruption to 4,500 years ago.

View into the crater

The Gambier limestone that forms the base layer for both Mount Schank and Mount Gambier contains abundant groundwater, which has played a role in determining the type of volcanic eruptions produced in each area. The craters at Mount Schank are at, or above, the level of the surrounding plain, and thus well above the groundwater table. This means that they have remained dry, unlike the Mount Gambier craters, which filled to become spectacular lakes.

The initial eruptions at Mount Schank occurred along a 1,200m long, north-west trending fissure in the underlying Gambier limestone and involved the venting of ash, followed by a lava flow. This fissure is now marked by a line of small scoria cones to the north-west of the mountain. Basalt lava flowed to the west and spread southwards over the flat terrain. Today, this lava is extensively quarried for road metal and these workings have been useful in studying the sequence of volcanic events. This first activity phase also produced a sizeable scoria cone and an ash ring, known as a maar.

Scoria cones north of Mount Schank

The second activity phase produced a new vent between the scoria cone and the ash ring (maar), forming a crater with a cone 100m in height (Mount Schank). The maar to the south was overlapped, but not completely buried, while the larger scoria cone was engulfed, but is still evident today as an inner rim at the northern end of the main crater.

Towards the end of the second phase a small explosion crater developed on the south-western flank of the main cone. Another small blowhole/ash ring was formed about 300 metres to the south east.

Additional information about Mount Schank is available in the Earth Resources Information Sheet M14, Volcanoes of the Mount Gambier Area (Office of Minerals and Energy Resources South Australia, July 2001).

History

The oral history of the Boandik people of south-eastern South Australia includes a story that suggests their ancestors witnessed volcanic activity in the Mount Gambier area. The Craitbul story tells of a giant ancestor, who made an oven to cook for his wife and family, at what is now Mount Muirhead. The groaning voice of a bird spirit warned them of evil spirits and so they fled to another site (Mount Schank) where they built another oven. Once more they were frightened off by the threat of the evil spirit and moved on to another place (Mount Gambier), where they again built their oven. One day water rose and the fire went out (the Blue Lake). They dug other ovens, but each time water rose, putting out the fires. This occurred four times, so Craitbul and his family finally settled in a cave on the side of the peak.

Mount Schank was named in December 1800 by Lieutenant (later Captain) James Grant, to honour Captain (later Admiral) John Schank of the Royal Navy. During his exploratory voyage along Australia's south-east coast Grant's wooden vessel, the HMS Lady Nelson, had sliding keels built to a scheme devised by Captain Schank. When Captain Matthew Flinders later sailed and mapped the same coastline, he adopted the names for any features already named by Grant.

Crater of Mt. Schanck 1844 Photo B 15276/4: State Library of SA

During 1844 George French Angas accompanied Governor Grey and his party on a journey to investigate the south-east coast of South Australia. His journal, Savage Life and Scenes in Australia and New Zealand (London) 1847, records a description of Mount Schank, in an entry dated May 5:

"At the foot of Mount Schanck [sic] are several caves; and in one of them … were found numerous organic remains, with bones of the emu and several gigantic species of kangaroo: also, a tooth, which must have belonged to a marsupial animal of prodigious size. Heaps of black cellular lava lie around the base of the crater, which rises very abruptly from the plain to an elevation of about 700 feet; the outer sides being clothed with grass, and scattered over with she-oak trees. On gaining the summit, a grand and stupendous scene opens to view. The rim or outer edge of the crater is not more than a couple of yards in breadth, and the interior of the mountain is one vast hollow basin upwards of two miles in circumference, and so deep that the trees growing in the rich soil of the windless valley at the bottom appear like miniature shrubs dotted over its surface. Looking beyond, the panorama is bounded only by the blue haze of immeasurable distance; and the line of the southern ocean stretches away until it is broken by the high land at Cape Nelson. The windings of the Glenelg … and the bold headland of Cape Northumberland, may all be traced from the brow of the crater. At the northern base of Mount Schanck [sic] there are more circular limestone basins, but they do not contain lakes; a spring of excellent water, however, rises in one of them, and near it I found growing several plants of the blue forget-me-not."

Mount Schank 1885 Photo B 45506: State Library of SA

In 1862 Father Julian Tenison Woods published his much-acclaimed first book Geological Observations in South Australia, which included an analysis of the volcanic regions of Mount Gambier and Mount Schank. His pioneer writings are recognised as the first systematic examinations of South Australia's geology.