This remote location is situated on the east coast of the Cape York peninsula, its sandwiched between the reef and the rainforest. It’s a very popular and picturesque spot for travellers exploring the cape with great camping spots scattered in amongst the palm trees. Quite often travellers will tackle the Frenchman’s Track as an alternative route to reach Chilli Beach. The beach is 4WD accessible for those wishing to explore beyond the camping grounds and its on the beach right next to the campgrounds where you’ll find this earthcache.
With much of the cape being sandy sandstone we were surprised to see a beach littered with granite boulders. Apparently about 300 million years ago Iron Range and surrounding areas was the scene of some violent volcanic activity. Explosions of red-hot pumice, dust and gases filled the skies while lava spewed out across the landscape. As layers of ash and pumice covered the land, they welded together to form welded tuffs - a very hard volcanic rock. Many years later a large body of molten magma rose from great depths, penetrating through the existing volcanic rocks. The magma slowly solidified beneath the surface to form granite. Today, the volcanoes have gone, and millions of years of weathering have carved the landscape to its present form. An obvious remaining landmark is Mount Tozer, to the south of GZ. It stands some 540 m above sea level and made of remnant volcanic rocks and granite. White quartz sand is found at Chilli Beach, which stretches between Cape Griffith and Cape Weymouth. This sand is derived from the coarse-grained granite of the ancient coastal hills.
Granite
Granite is a light-coloured igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth's surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles, and other minerals. This mineral composition usually gives granite a red, pink, grey, or white colour with dark mineral grains visible throughout the rock. The large mineral crystals in granite are evidence that it cooled slowly from molten rock material. That slow cooling had to have occurred beneath the Earth's surface and required a long period of time to occur. If they are today exposed at the surface, the only way that could happen is if the granite rocks were uplifted and the overlying sedimentary rocks were eroded.
Veins
A vein is a distinct sheet like body of crystallised minerals within a rock. Veins are found in association with all rock types and their dimensions vary in width and length.
Xenolith
A xenolith is a piece of rock trapped in another type of rock. It happens mostly in igneous rock when magma is fluid enough to flow round more solid rock. In igneous rock it can also be referred to as inclusion. The principle of an inclusion is that a rock containing an inclusion (fragment of another rock) must be younger than the inclusion. Eg. Inner rock is older than outer rock.
To claim a find on this earthcache. You will need to study the rocks at GZ and answer the following questions. Submit your answers via messenger or email. Go ahead and log your find on the cache, if there are any discrepancies in your answers I will contact you.
Q1. Describe the crystal size in the granite. Are they large or small? Based on what you see does this mean the granite was cooled quickly or slowly?
Q2. What colour are the rock veins that run through the rock and what rock are the veins likely to be?
Q3. Search the rocks till you find an xenolith. What colour are they?
Q4. Some rocks have large cracks in them. Why do you think this has happened?
Optional – add a photo of you and/or your gps chilling and Chilli beach.