500 million years ago
the LaTrobe Valley was covered by a deep sea. The seabed was covered by
slimy mud, the mud was compacted to become slate and mudstone, this process
took 100 million years.350 million
years ago the area was lifted and molten rock rose from deep in the Earth's
crust. When it cooled the molten rock became an Intrusive Igneous rock
called Granodiorite.
Glaciers swept across the LaTrobe Valley
around 230 million years ago, flattening and eroding the landscape.
The much harder rock Granodiorite was
exposed at the surface. Weather easily eroded the softer rocks, shale and
mudstone, while the Granodiorite remained intact and is now known as the Baw
Baw Plateau.
60 million years ago cracks called faults
formed in the Earth's crust. The LaTrobe Valley was formed by rock settling
between the faults.
The LaTrobe Valley naturally became a
swampy place, because the streams from the surrounding hills flowed into the
area. This was an excellent area for vegetation, which began the first step
of the coalification process.
But not all of the coal in the LaTrobe
Valley is the same age. The faults allowed blocks of land to drop a long way
and the swamps became lakes with sand and mud accumulating on the bottom.
Different areas of the swamp grew different vegetation this eventually
produced various types of coal, all within the same coal seam. This process
continued over a period of 45 million years
