In Australian Capital Territory, Australia
Size:  (not chosen)
How Geocaching Works
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From the trailhead, walk west along the well formed and marked trail to the Boboyan trig. Along the way, and especially at the trig, you will find a lot of slate type rock where rocks of the Ordovician period are metamorphosed (cordierite hornfels). This happens where they collide with the Granodiorite pluton (which looks like granite) of the Murrumbidgee Batholith.
Rock becomes metamorphosed when it is subjected to elevated pressures and temperatures. In a continent-continent collision, mountain-building forces bury rock many kilometres beneath the earth's surface. The weight of the overlying rock subjects the buried rock to enormous pressures. The internal heat of the earth gradually heats the buried' rock to extremely high temperatures. Under these conditions, the minerals in the buried rock react chemically with each other to form new mineral assemblages.
The original composition of the rock, together with the temperature and pressure to which it is subjected, determines what kind of metamorphic rock will form.
At the posted coordinates you will find a sign indicating the boundary between the two types of rock! Granite one side – slate the other! To log this cache, you will need to tell me the following information:
1. Which is older – the granite or the slate?
2. How many millions of years older?
3. What is the distance from the sign to the nearest point of the very large flat rock bed behind the sign?
Be sure to continue west down the path a little, down some nicely constructed steps, to a superb open viewing space on the pluton outcrop itself to behold the spectacular Granite Tor Views!
Feel free to post pictures of the magnificent views, the granite, or the masses of slate, but do not post any pictures that will help provide answers to the above!
You will need to bring a tape-measure to be able to log this cache!
(No hints available.)
Last Updated: on 6/1/2017 1:06:07 AM Pacific Daylight Time (8:06 AM GMT)
Coordinates are in the WGS84 datum