From granite to mud

[dg2008]

Question

Explain the surface process by which material that originated in grainte may eventually accumulate as a mud.

Weathering, erosion, transportation and deposition (750 words)

 

So far I have:

 

Granite, an igneous rock is formed deep within the Earth and cooled very slowly, to contain large crystals; quartz, white feldspar and mica.

 

Physical weathering, heating & cooling produce forces in the rock, expansion & contraction stress the rock. Eventually the forces begin to split the mineral form each other allowing water to seep along the grain boundaries. Freezing and thawing then liberates the grains. Once it's broken up, chemical weathering gets to grips on the surfaces. The main processes of chemical weathering are acids and oxidation, which often operate together. As rainwater dissolves carbon dioxide it is slightly acidic, this attacks the minerals in the rock. The feldspars and the micas are very susceptible to chemical weathering. The quartz is very resistant to chemical weathering.

During weathering, hydrogen ions break free their loosely bonded metal atoms. When this happens the structure collapses to form clay minerals.

The minerals are exposed to flowing water that lead to erosion. The grains as they are carried away pound, blast and scrape more debris to wear away the surface when they pass. The grains are also broken down as they move along to become smaller and more rounded.

 

Transportation of grains or sediment depends on the energy supplied by the transporting system and the size of the grains. Large grains settle to the stream bed, smaller grains roll or bounce along the stream bed and even smaller grains are picked up and carried along in suspension. The grains are also exposed to physical abrasion and chemical attack. Reactive minerals form clay minerals and dissolved ions while quartz is liberated. The transported grains eventually collide with the stream bed and each other. The rock fragments tend to become rounded by the abrasion, rather than broken by impact due to the water cushioning the impacts.

 

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Thats about it. For deposition should I talk about currents, flow rates etc, degree if sorting?

Also should I add more detail to above? like chemical equations, examples?

I think my main problem is refering it to mud.

[CaptainPanic]

I always learned that two major contributors to breaking down rocks are:

- plant roots (they squeeze into crevices and then push the two sides apart)

- water that freezes and expands

 

Note that I just wrote down what I learned in school when I was 14. I'm not an expert at all in this field.

[Theophrastus]

I did a similar project, (think of a science- fair type style, except without the liberty of choice for your field of study) earlier this semester, and yes, you have the essentials. I agree with captainpanic about the leaching of water into cracks in rocks, which increase in size as the water, freezing, expands. In regards to chemical equations, those, I find are quite key in making the work easily comprehensable and I recommend that you draw the crystal lattice structure of the initial and resulting minerals (examples of course) You should also mention that due to the greater surface area of crude protrusions, in contrast to flat surfaces, weathering is often spheroidal, resulting in a round- ish shape, which eases erosion and transportation of the rock. I'm not sure whether this is too late, given the time of the post, however, best of luck! Cheerio.

Edited May 30, 2009 by Theophrastus
a minor reform of ideas