10

Your concept of weathering is erroneous. It is not uncovering or stripping off material. Weathering is a very slow process of breaking down rocks, soil & minerals, in-situ, via contact with the Earth's atmosphere, water & biological organisms. This can also involve heat & pressure. Erosion, as you state, involves the moving of material. This can ...


8

Even rocks that have lasted for billions of years decompose when exposed to Earth's weather. What you have is indeed granite, but a somewhat decomposed granite, which is treated by geologists differently from the intact, solid stuff. The "crumbly bits" have their own name: grus. Granite is made of crystals of different minerals (mostly feldspar and ...


7

Yes, this is a granite. It's hard to know exactly which one. A geological map of the area shows the bedrock to be sedimentary rocks, so this piece of granite was transported in the creek from far away (but not too far, otherwise it will crumble completely). If we go further east, for example with this geological map, we find that: To the east, the ...


3

This answer is based on a cursory look at the 1:50000 Foglio Appiano, from the Geologic Map of Italy (in Italian Language only, as far as I can tell). As I pointed out in comment, I intend it as just a start for further investigations, which should be done with more detailed geological works and possibly more field work. I'd recommend contacting the office ...


2

Diabase is indeed relatively erosion resistant. One of the reasons is grain size. Consider the two other chemical equivalent of diabase: gabbro (coarse-grained) and basalt (glassy and fine-grained), which should potentially be similarly erosion resistant. This is not the case. Both gabbro and basalt erode very easily. Coarse-grained rocks, in general, ...


2

My understanding of supergene is that it is about mineral enrichment/concentration at the base of an oxidized zone, within a weathered profile. The seasonal/periodic rise and fall of the local water table is critical to supergene enrichment. The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ...


1

I don't see anything wrong with Supergenic. It is widely understood and includes weathering. I would stick to Supergenic if I were you. You probably realise that there are some rocks which, as they are produced in more than one way, would fit into several of your classification headings. There is no way of avoiding this. Quartz, for example, can be magmatic, ...


1

The case of a volcano blasting solid rock into smaller bits and pieces will generally still be regarded as weathering. Nonetheless, for your case to justify this statement, you could consider a glacier scouring through a fjord or rocky valley. However, the fact that particles have been 'stripped off' before they have engaged in transport processes by ...


1

It has been burned. No acidity etc. needed. If you throw one fist sized granit into a normal campfire (usually around 700 C) and leave it there to burn for some hours, when it cools it will crumble in your hands. As mentioned before "granite is made of crystals of different minerals" in intensive heat/cooling each mineral expands at a different rate and ...


1

My understanding of why granite decomposes that way is because it's formed under ground and as the over-burnden is removed so is weight and pressure. The granite formations are rounded as the outside layers fall away. We have very few freeze/thaw cycles in Arizona (Phoenix area), and not a lot of rain, but, we have tons and tons of decomposed granite in ...


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