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Activity page
6B
Here is a summary of the geological
stages of the formation of the Blue
Mountains, and diagrams to illustrate
those stages — but the diagrams are not
organised in order.
1 Read the information about the various
stages, then write the appropriate
number beside each diagram.
1
The Devonian Sea 400 million
years ago (mya)
2 Carboniferous Swamp 350 mya
Great Divide
Great Divide
3a
3b
Triassic Lake, 250–200 mya,
deposit of Wianamatta Shale,
formed when the sea rose and
the resulting dead vegetation
and marine life compressed to
form coal.
Triassic Lake, 250–200
mya, deposit of Hawkesbury
Sandstone as huge rivers from
the west carried sand sediments
that were layed down on top of
the shale.
Great
Divide
Blue
Mountains
Coastal Plain
Sea Bed
4
5
6
Triassic alluvial plain formed
when the layering of eroded soil
stopped.
First Earth Movement 170 mya,
volcanic activity meant that the
rocky bed rose to form a plateau
Second Earth Movement tilted
the plain, higher in the west than
the east, and erosion started to
produce the topography of today.
Great Divide
Great Divide
2 Add any information to
your summary table
on activity page 3A.
3 Write a brief paragraph or do a
comic strip sketch for your own
history textbook (in box 2 of activity
page 3B) to explain to readers how
the Blue Mountains were formed.
Great Divide
KEY
Basalt caps
Wianamatta Shales
Hawkesbury Sandstone
Narrabeen Sandstone
Coal measures
Older base rock
Vegetation
Sea
Great Divide
Eugene Stockton and John Merriman (eds), Blue Mountains Dreaming: The Aboriginal Heritage (2nd Edition),
Blue Mountain Education and Research Trust, Lawson, 2009, p. 14
Myths and Mysteries of the Crossing of the Blue Mountains
19