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.
While visiting the Gemfields, we noticed a prominent feature: rising out of the landscape is Policeman's Knob in Rubyvale. According to Intraplate Volcanism: In Eastern Australia and New Zealand by Robert Wallace Johnson, it is the oldest known intrusive basalt plug in the world, a result of eruptions in the Early Eocene Age, at around 56 Million years ago. More than 70 plug intrusions occur within an area approximately 50 km in diameter near to the present exposed eastern margin of the Drummond Basin. Some of the plugs form sharp hills and mountains while others are just low rises.
You can see Policeman's Knob very clearly from around the Rubyvale area and there are tracks off Goanna Flat Road that can be driven by a 4WD, or walked to get to the top - its' a great view.
So what is an intrusive plug? Basically, an old volcano where the lava flow stopped and cooled below a covering of earth (intrusion). In subsequent millennia, erosion has exposed the plug.
Normally, lava would flow to the suface and cool quickly, giving a particularly small crystalline structure called Basalt, and it is regarded as being extrusive rock (rather than intrusive [slow-cooling] rock). However, in some cases, rapid cooling can occur at or near the surface, resulting in similar basaltic crystalline rock. Such is the case at Policeman's Knob. Here is basalt, but the gases in the rock, because of the cooling, have formed holes (vesicles) inside the rock. You can see these vesicular textures in the rocks at Policeman's knob.
To claim this smiley, provide answers to the tasks below.
If you do not submit answers within a reasonable time, your log is likely to be deleted.
- What is the estimated age of Policeman's Knob?
- What kind of volcanic plug is it?
At the given coordinates, take a look at the rocks.
- What name is given to the texture of the rocks you see here?
- In your own words, describe the holes in the rocks.
- 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.
You are NOT required to do any research for the answers to the questions on this earth cache. Your answers come from the description given above, and your own observations.
When you have your responses 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 you can log your find in the meantime, and just say that you have MESSAGED your answers to the COs.
Again, you may log your Found It at any time, and if there is a problem with your answers, you will receive further correspondence.
Happy Earthcaching!