Follow the trail upwards, and around the side of a boulder-strewn hill. After that you climb up out of the trees onto a large expanse of bare rock. At this point you are on the exfoliation dome itself. This is a good place to stop and take a look at the coarse-grained porphyritic granite that makes up the majority of Enchanted Rock. "Porphyritic" is just a fancy geology word for an igneous rock that has one type of crystals that are much larger than the other crystals in the rock. Notice that the granite looks much different when it's not been chopped into pieces by faults.

This is the typical appearance of the granite that makes up Enchanted Rock. One of the interesting features of this granite is a weak alignment (at least in this image) of the large pink microcline feldspar crystals (megacrysts). In this image, you will notice that the pink crystals are aligned generally parallel to the pencil. In the park (and the Enchanted Rock Batholith as a whole) this alignment is typically parallel to the nearest contact between the granite and the surrounding rocks. When the granite magma was intruded into the surrounding rocks over a billion years ago, the magma was partly a very hot liquid and partly crystals (mushy). The crystals rotated in the liquid and ended up parallel to the granite margin.

This is not the best picture for showing magmatic foliation. For a better view of magmatic foliation from the Enchanted Rock Batholith, look at this image of a polished granite slab.

A more detailed physical and chemical description of the granite at Enchanted Rock


Geo-nerd note: I said "magmatic" foliation and I meant just that and nothing more. I don't think this is a flow foliation. I believe it formed due to stresses exerted during the emplacement process, not laminar flow.

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