There doesn't seem to be a lot of earthcache's up this way so thought I would add one for those driving this way and looking for something different to do. It shouldn't take to long to complete and will give you a chance to stretch your legs and admire this geological feature.
Bluff Rock and the surrounding area consists of granite rock which cooled from molten magma under the earth's surface about 225 million years ago. Subsequent uplift and erosion have exposed them to the earth's surface. According to geological theory, Bluff Rock stands above the surrounding area because it has been more resistant to erosion, probably due to having fewer cracks along which water can penetrate and accelerate the erosion process.
There is quite a bit of history associated with this area. This is part of the story that you will find on the plaque at GZ
The truth of that day remains clouded by many conflicting versions. One time Overseer at Bolivia Station, Thomas Keating, in describing the massacre as it had been told him by an old man at Bolivia, told of Aboriginal attacks on shepherds and sheep. Keating outlined how men on Bolivia Station were mustered and armed, then set out on the track of Aborigines to Pyes Creek on the western boundary of the property. According to Keating's story the Aboriginals were then attacked at Pyes Creek and they fled across country to Bluff Rock, where they were thrown from the top, killing most and injuring many. None of that tribe, which survived, were ever seen on Bolivia Station again.
Commissioner MacDonald reported that in October 1844 a shepherd had been killed by Aborigines on the Irby Station at Bolivia, but no retaliatory action was mentioned in the despatch. However, Edward Irby himself, when writing of the incident, describes how one of his shepherds, Robinson, had been killed by Aborigines and how four men had set out to find the culprits. In these few simple words he described in his journal the terrible deeds of that day:
However, Edward Irby himself, when writing of the incident, describes how one of his shepherds, Robinson, had been killed by Aborigines and how four men had set out to find the culprits. In these few simple words he described in his journal the terrible deeds of that day.
"The blacks saw us coming and hid themselves among the rocks. One in his haste, dropped poor Robinson`s coat so we knew we were onto the right tribe. If they had taken to their heels they might have got away, instead of doing so, they got their fighting men to attacks us. So we punished them severely and proved our superiority to them."
A very strong oral tradition exists amongst the local Aboriginal community of a baby surviving the fall in its mothers arms and being rescued and brought up by a nearby resident. The unmarked grove is said to be East of the rock and the present road.
WHAT IS GRANITE
Granite is a common type of felsic intrusive igneous rock which is granular and phaneritic in texture. The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. The term 'granite' also applies to a group of intrusive igneous rocks with similar textures and slight variations on composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphibole minerals. These form interlocking somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende) peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is known as a granite porphyry. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. By definition, granite is an igneous rock with at least 20% quartz and up to 65% alkali feldspar by volume. Granite differs from granodiorite in that at least 35% of the feldspar in granite is alkali feldspar as opposed to plagioclase; it is the potassium feldspar that gives many granites a distinctive pink color. The extrusive igneous rock equivalent of granite is rhyolite.
Granite is nearly always massive (lacking any internal structures), hard and tough, and therefore it has gained widespread use throughout human history, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 • 1019 Pa·s.Melting temperature is or 1215–1260 °C (2219–2300 °F)
Granite has poor primary permeability but strong secondary permeability.
Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids.
The term "granitic" means granite-like and is applied to granite and rocks of similar composition or texture.
Chemical composition
A worldwide average of the chemical composition of granite, by weight percent, based on 2485 analyses:
SiO272.04% (silica), Al2O314.42% (alumina), K2O4.12%, Na2O3.69%, CaO1.82%, FeO1.68%, Fe2O31.22%, MgO0.71%, TiO20.30%, P2O50.12%
MnO0.05%
LOGGING REQUIREMENTS.
There are 3 questions you will need to answer to obtain a smiley.
NO1
At GZ you will be standing beside a small monument with a plaque on it. On the plaque somewhere it mentions who named the rock. Who was it that named the rock formation. ?>
NO2
While standing at GZ look up at the rock in the distance, can you tell me the TWO main colours you can see on the rocky outcrop know as Bluff Rock from where you are?
NO3
Not far from GZ is a notice board with so great reading on it about the area. There is a sign on there that reads
BLUFF ROCKS
- - - - - - - -
THE MAKING OF A NATION
What is the missing word?
When you have gathered all the info needed send me an email with your answers please.
Zobo04 and I hope you enjoy this nice little earthcache and a break from driving. There is plenty of room to park near GZ. Bluff rock is very picturesque so don't forget to take your camera with you. Most of all enjoy 