Isopach

Isopachs are lines drawn through points of equal thickness. These maps are especially useful for geologist when it comes to identifying sedimentation deposits over a given area. These maps are also used to measure events such as volcanic eruptions. When needing ti identify areas with the largest amount of ash fall. This isopach map map shows ash fall from an eruption in Chilie in 1991.

Link: http://www.geo.mtu.edu/~ajdurant/hudson.htm