Here is some food for thought.
Have you ever noticed that the smaller features of rock (hand/footholds and smaller) almost always mimic the large scale gross features of the rock (ledges or even the entire rock itself)?
I’m not certain, but I’ll bet geologists have a term for this occurrence.
One of the inherently interesting things about rock climbing is the variance of the types of stone we encounter.
Granite chickenheads, the “eyebrows” of Looking Glass, Indian Creek splitters, the cobbles of Maple Canyon, etc.
I’ve been asked what my favorite rock type is for climbing and this is a question that I’ve never been able to fully answer.
I once thought that Yosemite cracks were the best until my first trip to the Colorado Plateau in Utah. At one time I thought that the edges of sandstone/limestone were the ultimate until I climbed the granite of City of Rocks or Devils Head.
I’ve always loved the features of Devils Lake metamorphic stone.
I guess that my favorite climbing medium is the next different and unique rock that I have not previously encountered.

I learned that the reason for the vertical splitters in Indian Creek has to do with how the rock is formed. Sandstone is a sedimentary rock, which means that it is made from sediment. In even simpler terms, it means sand settling to the bottom of a body of water. Because this settling occurs in horizontal layers, the strongest bonds are formed in a horizontal plane. Over time, the sediment becomes rock. When the rock is stressed, it will fault and crack. Because the strong bonds are in a horizontal plane, the cracks form along the vertical plane. That is why the cliffs are vertical and why the splitter cracks are too.

Devil's tower geology is pretty cool too. The tower was the core of a volcano that cooled and solidified. Then the cone of the volcano eroded away faster than the core leaving the tower.

Ah yes, The Tower. An igneous/basaltic intrusion of phonolite porphyry.
Since it is a solidified core of an ancient volcano, I guess you could call it a Laton Kor (latent core).
lol.

AJS,

Yes, this is exactly what I am trying to describe.
The micro simulates the macro.
Your analogy to table salt is spot on.
This is why you can get a gut feeling that a distant crag will be climbable even though you are viewing it from a long distance away.

'Rock' is fractal-like.

Shorelines, clouds, mountains, trees ... Benoit Mandelbrot mentions these as examples and motivation for studying fractals, a term he coined. Fractals are self-similar, that is they have the same structure on different scales. Zoom in or zoom out, you see the same kind of features.

Yes, rock can be fractal like, and you can see the same features at differing scales. It is incorrect to say that this is always the case.

In the example of your salt cube, that is a mineral, rocks are made up of a mixture of minerals that have different cooling rates and because of their chemical makeup, they weather and erode differently in different climate environments. The fracturing that they exhibit also can be very different based on the structural stresses that are applied to them.

Therefore, a limestone in a desert environment in a tectonically quiet basin setting is going to have fractures and erosional handholds that are quite different from those that it will have in a highly humid, tectonically active area.

John, sort of a simple rule of thumb for igneous rocks is that the bigger the phenocrysts are in the porphory, the deeper it was emplaced. When molten rock cools quickly the crystals don't have as much time to grow and the crystals are small. The extreme version of this is when it is vented directly to the air or water and obsidian (glass) is formed. When it cools slowly, down deep in Pluto's workshop, the crystals have time to grow. All minerals have different pressure and temperature ranges that they live in their different phases (liquid - solid - gas). Because of this, different minerals will crystalize at different pressure and temperature settings, i.e. the depth and temperature gradient of their area of emplacement. That is why you see those big crystals in a matrix of finer material that had already crystalized out.

Strangely, the minerals that are most stable at deep depths are the least stable at surface pressures and temperatures. In other words, rocks that live in the deep mantle erode very quickly on the surface. There is a list of these mineral assemblages in stability order called the Bowen reaction series. Wikipedia this for more info on the subject.

Hey Scott -

Am I translating correctly?

phenocrysts: inhomogeneities in the rock that cool/form at different temps/pressures than the bulk of the rock

porphory: the main bulk material of the rock


So instead of "those big crystals in a matrix of finer material that had already crystalized out" could be "phenocrysts in a matrix of porphory that had already crystalized out"?