The COSC (Collisional Orogeny in the Scandinavian Caledonides) scientific drilling project focuses on the study of mountain building processes in a major Paleozoic orogen. COSC-1, a 2500 m deep fully cored borehole through a hot allochthon and into the underlying thrust zone, was successfully drilled during the Spring and Summer of 2014 (see also session TS6.9/EMRP4.11/ERE1.6/SM6.8). COSC-2 will start drilling at a tectonostratigraphic level just below the bottom of COSC-1 and sample a complete section through the basal Caledonian detachment and enter the underlying basement of the Baltic Shield. COSC-2 is in the planning stage and funding is being applied for. In this splinter meeting we present the COSC-2 project and invite scientists to participate.