Systems, methods and kits relating to in-situ forming polymer foams for the treatment of aneurysms or fluid filled spaces are disclosed. The systems include an insertable medical device and an in-situ forming foam of lava like materials with a fast forming outer skin and a slower hardening interior that is formed from a one-, two- or multi-part formulation. When used to treat an aneurysm, the foam is placed into contact with at least a portion of an exterior surface of the medical device and/or the tissue surface of the aneurysm.