More volcanics

I seem to be on theme here with all things volcanic. So to continue...

Last week we explored the Limestone Coast of South Australia, the area south of Mount Gambier. I'll write more about the coast in the next blog but in the meantime it's hard to ignore the area's volcanic history because the two main mountains stand out from the plain. Mt Gambier and Mount Schank are the youngest volcanoes in Australia and are defined as dormant rather than extinct. They, and other volcanoes in the area, would have been quite a sight when active and there are local Aboriginal stories about the eruptions (thought to be about 5000 years ago).

Mount Gambier (left) and Mount Schank
as seen from Cape Northumberland near Port MacDonnell.

In 1800 Lieutenant James Grant, on board the Lady Nelson, thought he spotted four islands but as the ship moved closer the islands evolved into two capes he named Northumberland and Banks and two mountains he named Gambier and Schank.

Mount Schank as seen from Mount Gambier

Mount Schank

Blue Lake, Mount Gambier

The Blue Lake holds water because the crater is below the water table whereas the craters on Mount Schank is above the water table and dry. Scientists have worked out why the water in the Blue Lake turns to a brilliant turquoise blue early in summer each year and if you're interested I suggest you follow this link. 

Both mountains are maars, the result of the rising magma hitting shallow groundwater. Violent and spectacular. If another eruption were to occur in the area in the future it would cause widespread damage up to 100 km from the site.

A tale of dead fish

Instead of travelling back to Geelong from Colac on the Princes Highway we went north to Cressy to see what state the lakes are in. And this is what we found.

Lake Colac is almost dry - just a bit of water at the south end near Colac. And along the northern shoreline at Ondit there are thousands of dead European Carp. Of course they are a huge pest in our waterways so I don't mind them dying but it makes you wonder what else has died. We only notice the carp because they are so big. The boat ramp won't be used for a while.

Lake Cundare was also dry and because it's a saltier lake it was glistening in the sun. The whole area is a wetland of international significance! That's Mount Warrion in the background, yet another volcano on the volcanic plain.

OK, I've talked a fair bit about how dry the volcanic plains are. Maybe I'll give the topic a rest.

A hole in the ground

Many of the lakes on the volcanic plains don't have water in them but this large quarry at Ondit near Red Rock does. The Chesnut Teal, Coots and Black Ducks seemed to be enjoying it.

I know bluestone is essential as a crushed rock for road making and as a concrete aggregate. I know they use it to build up railway lines. I know they use it as building blocks and paving. But it does leave a rather big hole in the ground. At least it's not on the side of a mountain like the scoria quarries.

A sleeping elephant

When you grow up in an area you tend to ignore the features in the landscape. That's certainly true for me. I grew up on the Victorian Volcanic Plains, an area of lava flows covering 23 000 sq. kms. Many of the 400+ volcanoes that erupted over millions of years stand above the plain, looking spectacular, but we get so used to seeing them that we don't 'see' them.

The plains are flat - well, perhaps if you were riding a bicycle you'd disagree - so the low volcanoes can be seen from a great distance and were navigational points for the early settlers.

Mount Elephant is a stand-out scoria cone, 240 metres high with a crater 90 metres deep, and well known because it's on a highway. It used to be privately owned but the local community purchased it in 2000 and are replanting with indigenous grasses and herbs. Several years ago they organised a successful 'Music on the Mount' event, using the crater as a natural amphitheatre.

The second picture below was taken into the sun so looks very washed out, but it does show why it's called Mount Elephant. The lake in the foreground is Lake Gnarpurt, dry of course because most of our lakes are dry.

Wall to wall fencing

There are lots of stones on the Victorian Volcanic Plain. Lots and lots of stones. The plain is dotted with inactive volcanoes, and the evidence in the form of ash, tuff, scoria and stone is everywhere. It has dictated the type of farming, the type of vegetation and the type of fencing.

The area was first settled in the 1830s and by the end of the 1800s miles of dry stone fences had been constructed using the basalt rocks immediately to hand. Of course there were stonewallers and there were skilled stonewallers, illustrated by the two photos below.

The first is at a tourist stop at Derrinallum, with an explanatory board. It's a beautiful wall, with a double row of copestones on the top and larger throughstones placed at regular intervals. A real craftsman built this wall. The second is at Lake Condah, now part of Mt Eccles National Park. It's a very haphazard affair but I'm guessing a lot of hard work was involved nevertheless.

There has been a book written about the walls on the plains. It's called If These Walls Could Talk and I'm going to have to track down a copy in my library.

I'd also be very interested in knowing if anyone has researched the use of the walls by lizards and snakes, because their natural habitat is fast disappearing into stone crushers.

A plot reserved for the future

This afternoon I went out to the Bannockburn Cemetery, west of Geelong, to see what was flowering. The cemetery land was reserved in the 1800s, a large block for what turned out to be a small population, and most of the land remains as a remnant patch of what the volcanic plains grassland once was. It is now a protected flora reserve as well as a cemetery. All the vegetation in the photo below is natural to the area and the reserve is almost weed free.

I was very pleased to see Blue Devil was flowering, also Pink Bindweed and Lemon Beautyheads as well as wallaby grass and kangaroo grass - all are plants typical of the plains.

Feather-heads and Pussy-tails

It is always a surprise to see the feathery heads standing above the vegetation on the volcanic plains. And I'm not talking about birds.

The flowering stems of Feather-heads Ptilotus macrocephalus are about 60 cm tall and the flowers look a bit like bottlebrush flowers from a distance, but up close they have a beautiful woolly appearance. The long leaves are wide and strappy. The genus name Ptilotus means 'feathered wings', and the specific name macrocephalus means 'large head'. The fabulous Jean Galbraith in her book Wildflowers of South-East Australia said:

All eastern species [of Ptilotus] have large (1-6") terminal flower clusters like fluffy cylindrical brushes. Narrow shining flower segments are just visible through a mist of long hairs growing beneath them. Texture of segments usually everlasting-like.

We found the Feather-heads growing on open grassland when we were doing a plant survey on private property at Bannockburn yesterday. Grassland is a word used to mean an area with very few trees or shrubs. There were indeed many grasses – Kangaroo Grass, poas, spear grass and wallaby grasses - but we also found many species of herbs growing amongst the grasses – lilies, daisies, peas, orchids, pimeleas, goodenias, wahlenbergias. The grassland was looking very colourful.

After surveying the grassland we moved into an area classified as grassy woodland, and we found the Pussy-tails Ptilotus spathulatus. These are much harder to see because the leaves hug the ground and although the flower heads are vertical they are quite short. As their name indicates the leaves are spoon-shaped.

Galbraith's illustrator was Camilla Jakobson, and this is her drawing of the Ptilotus spathulatus.

Apparently both species of Ptilotus have huge taproots. I'll have to bow to the authorities in my reference books on this, because I haven't actually dug one up. But I have bought one. Today there was a Waterwise Expo at the Geelong Botanic Gardens, and the Friends had a plant sale. I couldn't walk past the Pussy-tails for sale. Now I have to decide which spot in my garden most replicates a 'grassy woodland'.

Grassy woodland survey

A group of us turned up at the private property at Bannockburn, set to survey a selected area of grassy woodland. And survey it we did. It took all day. Some of us walked the area to see what was growing there, some sampled the water in the creek for saltiness and oxygen levels and dipped the water for its invertebrates, some checked the insect pitfall traps, the mammal traps were checked, we looked and listened for the birds. There were some friendly and interesting discussions during rest breaks about identification of particular species.
It was a hot day and the vegetation showed the effect of many dry years but we saw many different plants flowering, including the nationally vulnerable Clover Glycine Glycine latrobeana. Several orchid species were flowering well - the Tiger Orchid Diuris sulphurea looked very handsome and the Sun-orchids were fully open in the sunshine. (Its exact identity wasn't clear but I think we decided it was the Plain Sun-orchid Thelymitra nuda or a near relative.)

A report will be given to the owners and the Catchment Management Authority, and results will be published in the Field Naturalists Club magazine. And the survey group will move on to investigate another private property in the near future. I'm already looking forward to it.
The aim is to build up the bank of knowledge about particular vegetation types on the volcanic plains. It's fun to do, and a terrific way for a novice to learn from the experts.

Grasslands Forever

Only 1% of the original vegetation on Victoria's volcanic plain remains, on roadsides, cemeteries, stock routes and in areas on private land that have been grazed but not cropped. Thankfully the volcanic nature of the plain meant that some areas have been impossible to plough.
The plains once supported a complex community of tussocks of Kangaroo Grass and other tussock grasses interspersed with a variety of lilies, orchids, daisies and other small herbs – 600 different species probably.
There is not enough effort being made to protect what we have left, and the loss of species and habitat is still happening. Even in reserved areas there are incremental losses of diversity over the years. Only the hardy plants are surviving because of changed fire regimes, weeds, man-made chemicals in soil and air, even climate change have an effect. And now we have machines that are capable of crushing the rocks on the plains, so we lose the fauna that use the rocks as shelter. Remnants need to be fenced and managed – strategic grazing, avoiding the use of fertilisers, weed control, a fire regime.
How can we make grasslands sexy? A lot of great work is being done by farmers, the Landcare organisation, Trust for Nature, Land for Wildlife. But a lot of the work involves planting trees and shrubs. Plains don't have trees and shrubs. And it is extremely difficult, if not impossible, to re-establish a grassland. We have to put money and effort into preserving what is left.