Isopach map- Volcanoes

This isopach map depicts the Rio Blanco tephra volcanic crater.   The  volcano has erupted, and the isopachs (connected circular lines) mark the extent of the ash and debris.  The smaller, brighter isopachs indicate areas closest to the eruption center, where there will most likely be heavy ash and debris.  The farther, wider Isopachs indicate areas where the eruption might reach, but the particulates and ash from the volcano not be very thick.  These maps account for environmental conditions like wind, rain, etc.http://www.geo.utexas.edu/faculty/barker/kempter/rbtephra.html