2. What causes foliation in metamorphic rocks? (Hint: there are two main factors

Question

2. What causes foliation in metamorphic rocks? (Hint: there are two main factors that allow foliation to form.) What can foliation tell you about the direction of applied stress during formation? Why do you think the non foliated rocks lack foliation? 3. List the rocks that display foliation. What are the most common mineral constituents found in these rocks that might produce foliation? 4. Consider layering in sedimentary rocks and foliation in metamorphic rocks from a geologic perspective. How does each form? Consider layering and foliation from an engineering perspective. Do you think layering and foliation would behave in a similar manner or a different manner if they are subjected to the same engineering conditions? 5. Explain why rock cleavage, which is a specific type of foliation, is important in the uses of some metamorphic rocks (hint: consider slate, which we commonly used for walkways or flagstone and previously used in roofing applications)

Explanation / Answer

2) . Temperature & pressure are the two main factors thart causes foliation in the metamorphic rocks. the main mechanism involved in the foliation is the shearing stress, which is the forces which pushes the rocks in the opposite directions.and the differential pressure is also the one, which forms layers parallel to the direction of application of force or perpendicular to the application of pressure ( as from the definition of pressure, as presure is the normal force per unit area). Non foliated rocks lacks foliation because of the absence of shearing stress & the differential pressure during its formation.

3) the rocks that produces foliation are : gneiss(biotite & granitoid gniess), schist , slate, phyllites .etc shows foliation. Mica & the chlorites are the common constituennts of these minerals which can cause foliation.

4) From the Geological perspective :

If we consider Layering in sedimentary rocks & foliation in metamorphic rocks :

based on their respective formations:

Foliation is formed by the difference in temperature & pressure or stresses while the layering is formed by thin embedding of both coarse and fine deposits of minerals such as mica over the rocks. Layering & foliation will behave in the different manner as foliation is the change in the shape of minerals bacause of temp & pressure while layering is the deposition of new minerals on the existing minerals

5) Importance of cleavage in the use of metamorphic rocks:

cleavage descibes the planar features of the rock.like its crystallography & its structures. by knowing the structure it is helpful in selecting the desired rocks for a particular construction.

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