Isopach

 

http://gulf.rice.edu/modBdel.html 

An isopach map illustrates the degree of thickness in a stratum (a layer of sedimentary rock with distinct characteristics). Isopachs are used to show areas of equal height. They are specifically used in stratigraphy and geology. The isopach map above shows thickening in the Brazos delta of Texas. Due to food deposits, the delta had experienced thickening of up to 50 centimeters. This data is from 1992.