diff --git a/src/module_definitions.f90 b/src/module_definitions.f90
index 52a532c288f73db2fda4f44bc483d53ffe245af0..84ac25f9caa0a5c2336573212e8078579a507594 100644
--- a/src/module_definitions.f90
+++ b/src/module_definitions.f90
@@ -325,6 +325,13 @@ module definitions
 
       end interface
 
+!=====[ZISODISP================================================================
+! type ziso is used to store the isostatic deflection of the basal boundary
+! due to isostasy
+
+      type ziso
+        double precision,dimension(:,:),pointer::zisodisp
+      end type ziso
 
 end module definitions