There is adequate parking for many cars in the roadside parking bay. Please be careful turning into this parking bay if you are coming up the hill.
Ancient foundations
Granite and gneiss outcrops at Collie, Esperance, Albany and Bremer Bay are the 'roots' of this mountain chain originally formed many kilometres below the Earth's surface. Under intense heat and pressure in the collision zone, the granite became "plastic' and mineral crystals gathered into tell tale bands as it was transformed to gneiss. It’s hard to believe that such tough resistant rocks that form these road cuttings behaved like plastic deep in the Earth’s crust.
Earthcache Lesson
Today’s Earthcache lesson is on folds. These old folds or 'olden foldies'.
Folds are created in rock when they experience compressional stress. This is when the rock is being pushed inward from both sides. This is like if you put a spring between your hands and push them together. As you push, you're compressing the spring, and rock can be compressed in the same way over long periods of time.
Folds are easily spotted in sedimentary rocks with clearly visible layers. Below is an example of folded mudstones and sandstones at Cape Liptrap in Victoria.
Folds can be classified in a number of different ways but today we are focusing on the angles of the fold limbs. Open, tight and isoclinal, are terms referring to the angle between two successive fold limbs.
An open fold is a gently curved surface where the rock has been squeezed a little.
A tight fold is when the rock has compressed quite a lot and the limbs are at a tight angle with each other.
An isoclinal fold has limbs that are parallel with each other and has been squished up a lot.
The fold types are depicted below. Use this diagram to classify the folds at GZ.
Earthcache questions
At GZ, carefully look at the rocks in the cutting. I have placed two piles of rocks on the ground in front of GZ (but I expect these to move over time). You can stand back and observe the folds.
Q1. Examine the road cutting and count the bends or folds in the rock. How many folds can you see?
By counting the folds, it means you have spotted them and ready for the next question.
Q2. Now that you have identified the folds in the rock, look at the angles of the layers either side of the bends. Based on this observation and folding diagram, are the folds open, tight or isoclinal? Why do you think this is the case?
Q3. More of a task than a question as a photo is required for the log. Walk up the hill by about 10m and capture an image of you or something important to you with the rocks in the background. A separate photo for each team member or a photo of the team is preferable.
Please log the cache straight away. You can submit the answers to the questions within a few days but logs without answers will be discreetly deleted within 14 days.
The cache was placed for WA goes BIG in 2022 hosted by WestOz Geocaching over the June long weekend.
