A Hole in Hypipamee EarthCache
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This cache is found on The Atherton Tablelands, west of Cairns in Far North Queensland.
It is accessed from the Kennedy Highway between Atherton and Ravenshoe.
The crater of Mt Hypipamee is a volcanic feature called a diatreme. A diatreme is the result of a single volcanic, explosive event. It is not the site of a volcanic eruption. There is very little, if any material usually associated with eruptions such as basalt, or scoria, or basaltic soils in the immediate vicinity. The rocks are granite and the soils granite based. Nearby, however, at S 17º 26.034’ E 145º 30.421’ is the top of a large shield volcano. If you approached the crater from Atherton you will have driven up a long spur to this area. From here you can look back and see how the thin liquid lava flowed many miles down towards Atherton and Malanda, and back towards Mt Hypipamee. It has been suggested that magma and gasses associated with this volcano in rising towards the surface of the earth found a weak area in the granite. Because granite is formed deep under ground it forms under immense pressure. As erosion removes the material above it, the surrounding pressure lessens so the interior pressure causes expansion which in turn leads to cracks and weak areas. One such area, possibly where two sets of parallel cracks intersected, was blown out, mainly by gas, like a cork out of a bottle. It has been rumoured that on a nearby farm there is a large granite rock lying on top of basalt material. Outside of glaciated areas, this is uncommon. I have not been able to find the said rock, however.
To log this cache, send the answers to the following questions, along with photos (a) of yourself or one of your party standing by the plaque at the site, and (b) of a view from the road at the top of the shield volcano.
1. From the plaque, what is the total known depth of the crater from where you stand.
2. What feature of the diagram supports the theory that the crater is associated with the shield volcano at the co-ordinates above.
3. What character of the sides of the crater supports the theory that it was formed where two sets of parallel cracks intersected.
Cheers, and Good Hunting!
Dan.
Additional Hints
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