The starting co ordinates will have you standing near an
information Rotunda on the now peaceful foreshore at Port Victoria
on the York Peninsula. 2000 million years ago it was a totally
different scene, volcanoes spewed ash and red-hot lava into the
atmosphere and earthquakes shook the ground.
The Port Victoria Geology Trail is a path above the beach that
heads south from the jetty to Rifle Butts Beach where you can
explore some different types of rocky outcrops formed by these
volcanoes.
These rocks have been affected by heat and pressure and were also
invaded by other rocks while they were well below the earth’s
surface. For the last few hundred million years they have been
exposed to surface wind, rain, sun and the sea. The effects of all
these processes can be seen on this great walking trail.
At the Jetty, not far from the rotunda, you can find two distinctly
different rocks formed by these volcanic eruptions.
Basalt:- The black rocks that contain a lot of iron
and magnesium. If you look closely you will see they also contain
light coloured minerals and Pink Feldspar:- This pink
Feldspar is called porphyry because it is made up of
two distinct crystal types. The larger ones were formed below the
surface before the eruption and the fine crystals formed when the
volcano erupted.
Further south you can find clearly layered pink and dark Feldspar,
the other layers were probably ash deposits.
A little further on again you can see some rocks containing the
bright green mineral called epidote. They have been
cut into blocks by quartz veins.
You then come to the possible eruption site at which you can see
broken angular fragments of mixed rock called
breccia
Further south past the boat ramp you can see layered volcanic rocks
that are cut by a wide band of light coloured rock, this structure
is called a dyke. These were feeders to the erupting
volcanoes higher up on the surface.
To claim a find for this cache you must collect some
information from the rotunda.
• 1. Explain what the brownish coloured staining is on some
of the Basalt
• 2. Explain how the above dykes were formed.
• 3. At what site number on this walk can you find the
breccia. (Possibly the eruption site.)
• 4. Post a picture of you and your GPSr in front of the
information rotunda or at your favourite site or rock
formation
Some teams are not
following these 4 simple steps. All future logs not following these
steps will be deleated.
Most of all enjoy the area and all it has
to offer.
We would like to offer special thanks to the BURTONS for
allowing us to place our earth cache close to their
GCZ31X PV Rocks , HEALTHY LEG for assisting with any
maintenance issues and the DISTRICT COUNCIL OF YORKE PENINSULA for
their assistance.