Tocumwal Blowhole
Welcome to my latest cache, “Tocumwal Blowhole”.
This is my first Earthcache, and I hope to provide some educational
and fun experiences to Geocachers who find themselves at this
cache.
The cache is based in Tocumwal, just north of the town, and is
centred on the Tocumwal Blowhole, a large hole in granite, well
actually two separate holes of different depths, that are alleged
to lead all the way to the Murray River, some 10 kilometres
distant.
The Blowhole is said to be sacred to the Ulupna and Bangaragn
Aboriginal Tribes. In times of drought and low water in the river,
the hole will bubble and overflow with water, like a fresh water
spring. There are two holes here of different depths. The larger
hole is said to be about 5m deep. There is a deeper narrower hole
which is rumoured to be about 20 to 25m deep. There is a hollowness
of sound on the south side of the larger hole that could be a
cavern.
Tocumwal
History Homepage
The Granite beds the Tocumwal Blowhole is formed in were laid
down in the Silurian Peroid around 416 to 443 million years ago.
Check out this Wikipedia page for more information on the Silurian
Period
Wikipedia Link
to Silurian Period
I have placed two pics of the blowhole area here. The top
picture shows the sign at the entrance to the blowhole area. In the
image to the left there appears to be a hole in the ground here,
full of water of course. This is the larger one they are referring
to in the description. To the right and out of image is the smaller
narrower and deeper hole. I have not provided a close up of the
granite in the area, for a reason.
All About Granite....
Well, what is granite. Granite is a holo-crystalline
quartz-bearing igneous rock. Granite has 10 to 50% of quartz as its
component. Granite also has Feldspar in the ratio between 65 to
90%, and the concentration of other minerals is less than 10%.
There are three main types of Granite:
Biotite-granite Includes quartz, plagioclase, biotite and
K-feldspar.
Hornblende-granite Also called Syenitic granite, contains
hornblende as well as mica.
Tourmaline-granite Composed mainly of Tourmaline, this
variety of granite exhibits a wide range of colors and is very
rarely available as white or colorless variety.
Of these three varieties, Biotite granite is the most
common.
Rather than just repeat information, follow this link to a
Wikipedia page on Granite.
Wikipedia Granite
Page
What you need to log this
cache.....
You will need to answer 3 questions and email me with the
answers to log this cache.
1. Using the above pictures, what type of Granite is
present at the Tocumwal Blowhole? For safety reasons, you do not
need to get too close to the holes to work this one out. Quite a
few people have been getting this wrong, so it is best to grab a
piece of granite and check the underside. If you have some water to
give it a little clean, that will help to identify it.
2. After reading the Wikipedia page on the Silurian
Period, tell me which two important things made their appearance in
this period. Hint: BF and VP.
3. Take a photo of yourself in front one of the circular
hole (the one not in the images above) and upload it with your log
entry. The photo is not required to successfully log the cache, but
it would be great wouldn't it to see the faces of all the people
who have gone to this site. Once again, you don't have to get too
close to take this photo for safety reasons.
That's all. Hope you have learnt something
in doing this cache. I love this area and wanted to bring it to the
attention of my fellow cachers and share the
experience.
Please be careful near the edge of the
holes. As the information states, they are quite deep. Even if you
are a good swimmer, be careful to stand back from the edge and
don't fall in. Keep a close eye on any children you take with you
to this cache. You will not need to get that close to the holes to
work out the Grantie type here.
Good luck and have fun.
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