Information
Things that you may find useful to help you complete this earthcache.
- This is a two waypoint earthcache. The two waypoints are 680 metres about via the street network, or 505 metres straight line apart.
- Camera or smartphone with photographic capabilities
- Your power of observation
June 2019
“Geocaching HQ, the Geological Society of America, and the EarthCache Reviewing Team have worked together to bring you a new update to the EarthCache Guidelines, for logging tasks. Effective immediately, photo requirements are permitted, but can only be included as an addition to well-developed logging tasks. A personal item must be an option for those who do not want to photograph themselves.”
The Geology
Imagine if you will, what happens if a tree falls in a forest. First off, it crashes to the ground and makes a lot of noise as it falls. Secondly, the tree, now being dead, like all dead things, will start to decay. This decay may take the form of the tree drying out, or, it may get rained on and become saturated before starting to rot away. Insects may begin eating and living in it. A larger animal may come and tear into the tree looking for insects to eat, hence accelerating the decay process by exposing the wood to oxygen.
Now imagine a tree falls and dies, but is buried in either mud, or maybe the tree falls into a body of water and is submerged thereby cutting it off from oxygen. If this happens the tree is not going to rot. It won't slowly decay and disappear; it's just going to stay there. So, what's going to happen to this tree? Buried in mud or sediments, the wood of a tree is slowly, bit by bit replaced by the dissolved minerals in the water or sediments. If it stays in place and is not exposed to any air, the cell structure of the wood will eventually be completely replaced by minerals, resulting in petrified wood. Sometimes, even the minute details of the tree can be preserved, things like knot holes, the wood grain, twigs and even bark.
Fossilised wood is interesting because there is such a variety, every single piece is different, depending on the species of the tree and the minerals that were present when it was being fossilised. You can get all sorts of different shapes, patterns and even colours so that you can enjoy and appreciate this really amazing fossil. The colour of the final product depends on the mineral composition. For instance, red colour comes from iron, black from carbon or manganese oxide, green is due to the presence of cobalt, chromium or copper, yellow results from iron oxide or uranium and manganese gives the stone hues of pink.
Tropical coniferous trees often don’t have the growth rings that you see in deciduous trees. Growth rings occur when there are growing seasons.
To understand how the petrification process that took place to turn trees to stone, let's take a closer look at some of the old logs on display here in Blackall.
At the published coordinates, you will find a petrified stump with two other small petrified logs. The small logs mark the corners of a garden bed. Examine the stump and logs taking note of structures you may notice and colours you see. Nearby is a model of the ‘Black Stump’, another famous log in Blackall. You will need to take a measuring device to the model to answer two of the logging tasks.
Proceed to waypoint 2 in Shamrock Street.
The process here is silica based, so you may see quartz crystals within the structure. Use your power of observation to answer the final logging task question.
Logging tasks
At GZ you will find an example of petrified wood with two smaller examples nearby, can you identify structures within these examples that lead you to determine that they were indeed trees in a previous life?
Near the published coordinates is a sculptured replica of the Black Stump, please post a photograph of the sculpture with a personal item that identifies your team (i.e. name badge, sheet of paper with team name, yourself).
At WPT 2, is another example of petrified wood, it is located in the median strip in the centre of the main street so be careful crossing to it. What two processes are responsible for the formation of this piece of petrified wood. Can you see quartz crystals within this example?
Petrified Tree in Ginkgo Petrified Forest State Park
Washington State USA
To successfully log this Earth Cache please message me, preferably via the message centre or via email here, your answers to the above logging tasks: (If you would like to do a basic log to keep your stats and TB distance in order that is fine.