An isopach map () illustrates thickness variations within a tabular unit, layer or

stratum In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

. Isopachs are

contour line A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional grap ...

s of equal thickness over an area. Isopach maps are utilized in hydrographic survey,

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

sedimentology Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of mo ...

structural geology Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover informatio ...

petroleum geology Petroleum geology is the study of origin, occurrence, movement, accumulation, and exploration of hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). Sedime ...

and

volcanology Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma and related geological, geophysical and geochemical phenomena (volcanism). The term ''volcanology'' is derived from the Latin word ''vulcan''. Vulcan was the anci ...

. An isopach map is similar to an isochore map, but these terms actually describe different methods of displaying thickness variations within a layer.Levorsen (1967), p. 596-600 and 616.Tearpock and Bischke (2002), chap. 14. *An isopach map displays lines of equal thickness in a layer where the thicknesses are measured perpendicular to the layer boundaries. Isopach maps are also referred to as True Stratigraphic Thickness (TST) maps.''Isopach maps vs isochore maps'' a
www.structuralgeology.org
accessed 5 April 2013. *An isochore map displays lines of equal thickness in a layer where the thicknesses are measured vertically. Isochore maps in geology are also referred to as True Vertical Thickness (TVT) maps. Thus, an isochore and isopach map are the same only when both the top and bottom surfaces of the layer shown are horizontal. When the layer shown is inclined, as is usually the case, the thicknesses displayed in an isochore map of the layer will be greater than the thicknesses displayed in an isopach map of the same layer. The terms isopach and isochore are widely confused, and many times maps of True Vertical Thickness (TVT), which by definition are isochore maps, are incorrectly labeled isopach maps.

Notes

References

* Levorsen, A.I. (1967), ''Geology of Petroleum,'' W.H.Freeman and Company, San Francisco, 724 p. * Tearpock, Daniel J. and Bischke, Richard E. (2002), ''Applied Subsurface Geological Mapping with Structural Methods (2nd Edition),'' Prentice- Hall, Englewood Cliffs 822 p.

External links

Oilfield Glossary
Map types Sedimentology Stratigraphy {{geology-stub he:מפה גאולוגית#מפה איזופכית