what is foliation?

Answer 1

Foliation is any penetrative planar fabric present in rocks. Foliation is common to rocks affected by regional metamorphic compression typical of orogenic belts. Rocks exhibiting foliation include the typical metamorphic rock sequence of slate, phyllite, schist and gneiss. The slatey cleavage typical of slate is due to the parallel growth of microscopic mica crystals. In gneiss the foliation is more typically represented by compositional banding due to segregation of mineral phases. Foliated rock is also known as S-tectonite in sheared rock masses.

Formation Mechanisms
Foliation is usually formed by the preferred orientation of minerals within a rock.

Typically this is a result of some physical force, and its effect upon the growth of minerals. The planar fabric of a foliation typically forms at right angles to the principal stress direction. In areas of shearing, however, planar fabric within a rock may not be directly perpendicular to the principal stress direction due to rotation, mass transport and shortening.

Foliation may be formed by realignment of micas and clays via physical rotation of the minerals within the rock. Often this foliation is associated with diagenetic metamorphism and low-grade burial metamorphism. Foliation may parallel original sedimentary bedding, but more often is oriented at some angle to it.

The growth of platey minerals, typically of the mica group, as a result of prograde metamorphic reactions during deformation. Often, retrograde metamorphism will not form a foliation because unroofing of a metamorphic belt is not accompanied by significant compressive stress. Thermal metamorphism in the aureole of a granite is also unlikely to result in growth of mica in a foliation, although growth of new minerals may overprint existing foliation(s).

Alignment of tabular minerals in metamorphic rocks, igneous rocks and intrusive rocks may form a foliation. Typical examples of metamorphic rocks include porphyroblastic schists where large, oblate minerals form an alignment either due to growth or rotation in the groundmass.

Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers, especially ultramafic intrusions, and typically plagioclase laths. Granite may form foliation due to frictional drag on viscous magma by the wall rocks. Lavas may preserve a flow foliation, or even compressed eutaxitic texture, typically in highly viscous felsic agglomerate, welded tuff and pyroclastic surge deposits.

Metamorphic differentiation, typical of gneisses, is caused by chemical and compositional banding within the metamorphic rock mass. Usually this represents the protolith chemistry, which forms distinct mineral assemblages. However, compositional banding can be the result of nucleation processes which cause chemical and mineralogical differentiation into bands. This typically follows the same principle as mica growth, perpendicular to the principla stress. Metamorphic differentiation can be present at angles to protolith compositional banding.

Crenulation and intersection lineations are particular types of foliation.

You could get more information from the link below...

Answer 2

In mathematics, a foliation is a geometric device used to study manifolds. Informally speaking, a foliation is a kind of "clothing" worn on a manifold, cut from a stripy fabric. On each sufficiently small piece of the manifold, these stripes give the manifold a local product structure. This product structure does not have to be consistent outside local patches (i. e. well-defined globally): a stripe followed around long enough might return to a different, nearby stripe.

Answer 3

fo·li·a·tion /ˌfoʊliˈeɪʃən/ Pronunciation Key - Show Spelled Pronunciation[foh-lee-ey-shuhn] Pronunciation Key - Show IPA Pronunciation
–noun
1.the act or process of putting forth leaves.
2.the state of being in leaf.
3.Botany.
a.the arrangement of leaves within a bud.
b.the arrangement of leaves on a plant.
4.leaves or foliage.
5.Printing. the consecutive numbering of the folios or leaves, as distinguished from pages, of a manuscript or book.
6.the total number of such leaves.
7.Petrology. a form of lamination produced in rocks by metamorphism.
8.ornamentation with foliage, or an arrangement of foliage.
9.Architecture.
a.ornamentation with foils.
b.ornamentation with representations of foliage.
10.formation into thin sheets.
11.the application of foil to glass to make a mirror.
[Origin: 1615–25; foliate + -ion]
Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
American Heritage Dictionary - Cite This Source
fo·li·a·tion (fō'lē-ā'shən) Pronunciation Key
n.

1. The state of being in leaf.
2. Decoration with sculpted or painted foliage.
3. Architecture Decoration of an opening with cusps and foils, as in Gothic tracery.
4.
1. The act, process, or product of forming metal into thin leaf or foil.
2. The act or process of coating glass with metal foil.
3. The process of numbering consecutively the leaves of a book or manuscript.
4. The leaves so numbered.
5.
1. The process of numbering consecutively the leaves of a book or manuscript.
2. The leaves so numbered.
6. Geology The layered structure common to metamorphic rocks.


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The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
WordNet - Cite This Source
foliation

noun
1. (botany) the process of forming leaves
2. (geology) the arrangement of leaflike layers in a rock
3. (architecture) leaf-like architectural ornament
4. the production of foil by cutting or beating metal into thin leaves
5. the work of coating glass with metal foil

WordNet® 2.1, © 2005 Princeton University

Answer 4

I think you mean the erosion kind of foliation, yes?

http://en.wikipedia.org/wiki/Foliation_(geology)