How do you describe foliation?
Foliation in geology refers to repetitive layering in metamorphic rocks. Each layer can be as thin as a sheet of paper, or over a meter in thickness. The word comes from the Latin folium, meaning “leaf”, and refers to the sheet-like planar structure.
What is foliation and what causes it?
Foliation – This represents a distinct plane of weakness in the rock. Foliation is caused by the re-alignment of minerals when they are subjected to high pressure and temperature. Well developed foliation is characteristic of most metamorphic rocks. Metamorphic rocks often break easily along foliation planes.
How can you tell if a rock has foliation?
Foliated texture is further subdivided based on the presence or absence of pronounced color banding in the rock. Rocks without distinct alternating bands of light and dark minerals are described a nonlayered, whereas rocks with alternating bands of dark and light minerals are described as layered.
What does foliation tell you in a metamorphic rock?
The rocks become foliated, that is the texture sequence of slaty cleavage to schsitosity, to banded, or the rock sequence slate to phyllite to schist to gneiss. Thus, metamorphic rocks not only tell us the kind of metamorphism, they are also a measure of the intensity of metamorphism.
What does foliated mean in rocks for kids?
Foliated rock is a type of metamorphic rock that has distinct, repetitive layers. Sometimes these layers are very differently textured or colored.
Where do foliated rocks form?
Foliated metamorphic rocks are formed within the Earth’s interior under extremely high pressures that are unequal, occurring when the pressure is greater in one direction than in the others (directed pressure).
What does foliation look like?
Foliation often occurs parallel to original bedding, but it may not be ostensibly related to any other structural direction. Foliation among the gneisses appears as distinct alternating bands of platy minerals and coarse-grained minerals; however, gneisses do not split, or cleave, along their planes as schists do.
What is the difference between foliated and Nonfoliated rocks?
Foliated metamorphic rocks exhibit layers or stripes caused by the elongation and alignment of minerals in the rock as it undergoes metamorphism. In contrast, nonfoliated metamorphic rocks do not contain minerals that align during metamorphism and do not appear layered.
What is the significance of foliation?
The presence of foliation is a clue to metamorphic rocks. The resulting foliation is coarser and more distinct than that of slate. Rock foliations and lineations are indistinct or lacking. Commonly a lineation lies in the plane of a foliation in the same rock.
Is foliation sedimentary rock?
A foliation is any sort of fabric-forming planar or curved planar geologic structure in a metamorphic rock, but could additionally include sedimentary bedding or magmatic layering (Wilkerson, 2019). A foliated rock holds a parallel alignment of certain minerals that are repetitively layered.