On the basis of new geophysical data acquired by the Federal Institute of Geosciences and Natural Resources (BGR) and the Polar Marine Geological Research Expedition (PMGRE) as well as existing data new geophysical maps were compiled for the Lazarev Sea and the Riiser-Larsen Sea between 10 degrees W and 25 degrees E. The new results are: The drastic change in the strike direction of the volcanic Explora Wedge between longitudes 10 degrees W and 5 degrees W is accompanied with a gradual change from one major wedge, i.e. the Explora Wedge, into at least two wedge-shaped volcanic constructions, each manifested by a sequence of seaward-dipping reflectors in the seismic records. The southern Lazarev Sea is best described as a continental margin affected by multiple rifting episodes accompanied with transient volcanism. A distinct N80 degrees E striking basement depression separates the volcanic-prone continental margin of the southern Lazarev Sea from oceanic crust upon which the Maud Rise rests. (mod. journ. abst.)