Image from http://home.iprimus.com.au/foo7/volcmap.html
http://en.wikipedia.org/wiki/Epping,_Victoria
Merri Creek management committee (which now cares for a platypus)
http://www.mcmc.org.au/index.php?option ... temid=341/
During the Tertiary period, volcanoes deposited basalts on top of the Silurian rock (the Older Basalts). Sands were deposited over the top of the Silurian rock when the area was submerged again under the sea during the Tertiary period. These sands have been eroded away by the creeks in the last few million years, leaving deposits of Tertiary sands (the Brighton Group sands) on the ridges. Since that time the spread of lava southwards from twelve separate eruption points in the area between Wallan and Craigieburn formed the basalt plains characteristic of the catchment. These basalts are called the Newer Basalts. The youngest of these lava flows was from either Mount Fraser or Hayes Hill some 800,000 years ago[84]. These flows followed and filled former valleys of the Merri and Darebin Creeks extending south to the valley of the Yarra River and then westward along the Yarra valley to the vicinity of Spencer Street in Melbourne.
With the lava surface sloping down towards the east and south from these eruption points, the course of the ancestral Merri Creek came to be determined by natural depressions and ridges in the lava surface and by the major fractures and joints in the volcanic rock.
In places the lava flows blocked the ancestral Merri Creek or its tributaries, creating lakes or swamps that filled with sediment forming flat plains that are characteristic of the area immediately to the south of Wallan. Other such ancient swamps are scattered along the Creek.
Today parts of the beds of the Creek and its tributaries have cut through the basalt to the underlying Silurian rock. An example of the Silurian rock outcropping is in the cliffs of the Edgars Creek valley in the vicinity of Tilley Street Coburg North.
http://www.mcmc.org.au/index.php?option ... Itemid=306
http://home.iprimus.com.au/foo7/volcmap.html
The Victorian Volcanic Plains are located in Western Victoria and covers over 2.3 million ha (10.36% of the State).
It stretches from Portland in the west to Craigieburn in the east and from Clunes in the north to Colac in the south.
At Fairfield the basalt blocked the Yarra river and formed a large lake and water fall. The Lake went back to Warburton. All was undone when it finally eroded the sandstone on the Kew side. If you cross the river here one side (n) has basalt (The cutting the freeway shows a flow) and the other side (s) folded sandstone.
This material moves!
Lay concrete thicker than standard so you can 'float' over it. Keilor cops the worst of it though.