Wollangambe- erosion issues?

[Kapriel]

The most recent TPOD was interesting. But...I wonder if we might not take a closer look at the way those particular mountains tend to erode?
Mentioned in the TPOD is a site called Mount Banks. Looking at the severely cut bluff, I can see why at first blush one might assume that was EDM'ed rather than eroded in the normal way. I've (hopefully successfully) attached the image of Mount Banks (linked in the TPOD). Note the talus slopes are visible in google maps, covered with brush. There is a clearly marked river following the contour of the bluff.

Now let's look at the surrounding areas to see if this kind of sharply cut bluff is at all common to the area. North and east of the Mount Banks area is Mt Tomah, and the spot I've chosen for the comp. shot is just south and east of that. In the lower left corner of the image (viewing in google earth) is a second example of a sharply cut bluff, though in a much earlier state of development. Note the small talus slope collecting below the harder layer of rock. Soft rock erodes faster than hard rock, leaving a ledge or lip overhanging the talus slope. (again-hopefully I've correctly attached the pics in question).

I don't see how this can be a candidate for an EDM'ed landscape. These are the links used as evidence that the Wollangambe crater is the result of a thunderbolt, and so that's why I was taking a look at it. Thoughts? Do I have the right places, as linked/noted in the TPOD?

[ps-reviewing the images I attached, they are in reverse order, so the top image is the second of the two I mentioned, and the second of the first I mentioned. sorry for the confusion]

[The Great Dog]

The slope below Mt. Banks isn't a talus slope, it is a 45 degree "shoulder" that many geological Picture of the Day articles have mentioned. Mt. banks images:







Monument Valley:



If the gum trees were removed from the Mt. Banks region, the shoulders would be more visible. As it is, one can see that the shoulders are only thinly covered with debris.

The same structures are found in Amazonia:

[Kapriel]

Great pics! Totally magnificent. That one with the guy standing in front is amazing. Beneath his feet we can clearly see a harder layer of stone with its softer, more easily eroded underbelly showing very clearly.

I wish I could personally feel more certain about the EDM origin of this feature. At the moment, I still don't quite see why those shoulders could possitively not have been material that was eroded from layers of softer sediment that once used to lie above the current top-ridge of rock. Softer layers lying above the harder layers would have eroded down to the shoulder area, and become lithified as shoulders in their turn. The harder layers would have remained, just as we see them. There is also a river, and rivers have been known to erode sheer faces on cliffs. It completely depends on the material being eroded. Can we positively prove that this cliff was not river-eroded? Just playing devil's advocate. I'd be happy to be wrong.

I'd also like to know (but can't seem to find anything about it online) if there is a fault running through there.

It would be good to make up a short list of "necessary pre-requisites" to help us define which features are EDM'd and which were erosional. For example:

Would EDM'd features have resulted in a preponderance of powdery material vs the grittier, more granular material of normally formed sedimentary beds (sandstone, etc)? What size particles are left from laboratory experiments using electric arc machining? The plates I've seen pictures of have been ceramic, I think. (will have to check). Since ceramic is a clay, essentially, the particles would be finer than sand. Has EDM been attempted on materials other than clay or ceramic plates? And if so, what is the result?

Are larger particles EDM'd the same way smaller ones are? In other words, do they react to the electrical arc exactly the same way, and make the same patterns? Are they flung further or shorter distances from the central trench? Are certain elements liberated from the rock during the EDM process? Is the material changed in any way?

Is there a mathematical proportion that describes how deep the trench will be, given a certain substance being machined, and how is this affected by changes in the strength of the electrical arc? In short, what are all the factors that determine the shape and composition of the end result?

Just stuff to consider.