Void-fill structure (known in some texts as simply a geopetal structure) is a void or cavity in a rock that has been part-filled with sediments or mineral deposits, that indicates an initial horizontal that can be used as a way up structure and as a precise measure of post-depositional tilting.

In general, geopetal seems to be used in the U.S., while way up structure is used in the UK.

Mr Matt according to me the peace in Somalia can come into existence through bottom up structure.