This is an EarthCache and has special requirements for logging it. You cannot log a Found It without responding to the logging requirements set out below.
Only one find claim per Message. Each Geocacher claiming a find must submit an individual response. One team can not lodge a response on behalf of a group of people.
Hopefully, after visiting this site, you will have an expanded appreciation of the wonders of our natural environment, and recognise that the environment here has a rather rare geological feature.
Getting there.
The coordinates will be found along a walking trail called The Coolibah Walk along the banks of the Barcoo River. The walk is part of another Mystery Cache. There is also another Earth Cache along this trail.
If you wish to complete all three caches, the best parking is found at Parking Area 1.
If you wish to complete just THIS Earth Cache, then park at Parking Area 2.
The Theory - Part One
Magma is composed of molten rock and is stored under the Earth's crust. It's that yellow portion on the Earth Cache Logo (although the diagram is a bit out of proportion). Magma is a molten and semi-molten rock mixture usually made up of four parts: a hot liquid base, called the melt; minerals crystallized by the melt; solid rocks incorporated into the melt from the surrounding confines; and dissolved gases.
The main components of the gases are water, carbon dioxide, and sulphur either as sulphur dioxide or hydrogen sulphide. In addition, there are small amounts of nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen. Phew!
When Magma erupts onto the Earth's surface it is usually because of internal gas pressure, (I know what that's like!) and then it becomes known as Lava. Naturally, it cools, and the rate of cooling determines different rock structures and mineral/crystalline content. That aside, what happens to the dissolved gases?
Well, having escaped from a high-pressure state, the lava is no longer able to confine the gases within, so they expand and form small gas bubbles of varying sizes, called vesicles.
Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many vesicles at its surface and inside.
The Theory - Part Two
OK, so once our rocks have eventually cooled, they enter into further stages of development. One stage involves the elements of wind, water (rain), ice, and even the process of freezing and thawing. Over time, and we are talking of thousands or millions of years, pieces of rock break off the mountain. These pieces fall because of gravity, breaking them into smaller pieces. The rocks may hit other rocks below and break them, too. Water, in oceans, rivers, and lakes, rushes against rocks, wearing away bigger pieces until they become tiny grains. After many years, the rocks become so small that we call them sand.
Most sands gather in places like deserts or beaches. Other sands are not so "free-standing", but are transported to places where they settle - a process called sedimentation. Another time more sand is layered on top with silt and clay: this fine-grained stuff is called Matrix. This process cycles, with other materials comprised of quartz, calcium carbonate or iron oxide - this is the cement: mineral matter, introduced later, that binds the sediment into rock. All this is settling between the grains of sand. Under the pressure of gravity from all the materials above (think tons of desert sand or water in a lake), the layers of sand are cemented together and sandstone is formed.
It is not a perfect process, and often, spaces are left during the cementation process. The holes that are left are great places for storing water or oil. Some sandstones have more holes than others depending on the amount of calcite or quartz that fills in between the sand grains.
Sandstone rocks with holes are known as porous sandstones. Porosity is the percentage of empty space in a rock. For most rocks, porosity varies from less than 1% to 40%.
The Logging Task - Part One
Identify the missing words that would complete the following:
A feature that is common in many volcanic rocks forms when ______ is brought to the earth's surface which is then called _________.
Gasses may form small cavities called _______.
When describing the texture of such rocks, the term ________________ ___________ is used.
The Logging Task - Part Two
Identify the missing words that would complete the following:
Sandstone is the result of a process called ______________ where grains of sand are mixed with ___________ (the fine-grained stuff) and _________ (the mineral stuff).
Often holes are left, causing the sandstone to become ___________.
The percentage of empty space in a rock like sandstone is called its ____________.
The Observation
At the given coordinates, you will find an example of rock as described above. Examine the rock carefully (sight and touch), then complete your logging task in Part Three.
The Logging Task - Part Three
The rock here is called ________________.
Therefore briefly explain why you see a either vesicular texture, or an example of porosity.
The Logging Task - Part Four
Take of photo of yourself OR your GPS to show a view of GZ. Include it in your message, but please do not post it in your log, it might give too much away.
When you have your response to the above questions, please, if possible, Message us, using the link at the top of the page underneath the name of the Cache. We prefer the Message method, as apparently, we don't respond to emails very well, but messages we do. We will contact you by Message once your Message has been received.
But please log your Found It 
in the meantime, and just say that you have Messaged your answers to the CO. We do reply to all logs within a reasonable time, and if there is a problem with your answers, we will ask you for further clarification.
Happy Earthcaching!