It folds and ripples occur in rocks in the Earth's crust as a result of the forces of compression and these structures are no particular layers in sedimentary rocks and igneous and metamorphic rocks of class

Pleat parts
1_almistoy axial Axial plane
    A surface that divides the fold into two almost identical. It may be the level of the axis of folds vertically or diagonally or horizontally depending on the quality and character of the fold to be the dominant axis of the fold level horizontally .ala that sometimes be convex or concave surface and the axis of the fold Athddatjah level trends tennis lines. Strike
2_mahor Pleat Fold Axis
    Is the line that represents the intersection of the level of the fold axis of the fold in the case of symmetrical and natural folds is oblique, the fold axis corresponds to the top line, but in other cases Kalttiyat accumbens and inverted, the axis of the fold to the top line with Aattabq
3_oheme aside Pleat, extends wing fold axis of the level of certain herewith to the next level of the fold, and that each wing be shared between Titin Mottagaozatan Hkl1-10
4_ top line Crest line
      Is the line that connects the summit points that form 1-10
5_ top surface Crest surface
        It is the surface which connects all the top lines of the layers forming the fold Hkl1_10
Most studies Alehiologih does not care much distinction between the top and the axis or between the top level
Axis level. Because this distinction has to be attached only in the study of oil and natural gas pools in the folds convex structures, where it becomes discrimination at the top level and the level of focus necessary.
6_ bottom fold Trough
     Fold the bottom is the point with the slightest level of Fold concave. There is the bottom layer of each constituent Fold concave layers.
7_kht bottom Trough line
   Etc. is connecting the dots in the lower fold the bottom of the concave shape of 1_10
8_mistoy bottom Trough line
Is the level that is located attic bottoms constituent layers Fold lines.
9_toul Pleat Fold length
Is the amount of extension along the fold lines racket layers, length varies greatly and may reach into the tens or hundreds of kilometers[1]

([1]) _د.فلاح شاكر اسود،الخرائط الموضوعية.رقم الطبعة 316،السنة 1991، ص31