The Balkan anomaly (Figure A12) is located below south-eastern Europe and overlies the core-mantle boundary. It was first identified in van der Meer et al. (2010). The Emporios slab and Mesopotamia slab to the northeast, both higher in the mantle and correlated to geological records of Jurassic and younger subduction, were used to infer to interpret the anomaly as the Balkan slab representing lithosphere that subducted prior to the Jurassic age. The Mongol-Okhotsk subduction in the east constrains the Siberia block to a Triassic to Jurassic position northeast of the Balkan slab. The Balkan slab therefore is likely the result of subduction to the west of Siberia. The Al Jawf slab, interpreted as subducted Paleotethyan lithosphere, suggests a subduction location of the Balkan slab northwest of southern Laurasia. Van der Meer et al. (2010) considered the Solonker Ocean that subducted between the North China block and Amuria until Triassic time (Xiao et al., 2010), and the Uralian ocean that intervened Siberia and Baltica as potential sources of this slab. The position of this slab in the light of global plate reconstructions makes a correlation to the Uralian Ocean more likely. The collision between Siberia and Baltica occurred in the Late Permian (~280-250 Ma) (Cocks and Torsvik, 2007; 2011; Torsvik et al., 2012), which we adopt as the age for the top of the Balkan slab. In the S40RTS model the Balkan slab is part of a much larger NW-SE trending anomaly of >4000 km, from the North Sea to Anatolia, where it connects to the Al Jawf slab. This large extent may represent a a more complete record of the Permian Uralian Ocean, but in the UUP07 model only the Balkan slab (<2000km) is detected.