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.