The Norwegian Antarctic Research Expedition 1978–79 used the Scott Polar Research Institute Mk IV radio echo-sounding system fitted in a Bell 206B helicopter to survey 620 km of Riiser-Larsenisen and 100 km across the outer part of Stancomb-Wills Ice Stream. Observed thicknesses of Riiser-Larsenisen decrease from 700 m at the grounding line to less than 200 m at the ice front. The thickness of Bllenga ice rise varied between 200 and 450 m. The ice shelf thins towards the east, and seems there to flow obliquely to the ice front (Fig.1).

Step-like change in thickness of >150 m over 500 m horizontal distance i s observed in the central part of the ice shelf. The records also demonstrate undulations in ice thickness of 600 to 700 m wavelength and 50 m amplitude, and various types of rifts and crevasses. Internal layering is recorded at 250 to 300 m depth over Blåenga and i n the ice shelf up-stream of this ice rise.

Observed ice thicknesses on Stancomb-Wills Ice Stream range from 130 to 220 m, with no systematic decrease towards the ice front. The records include long sections of heavy scatter from densely spaced rifts and bottom crevasses. This ice stream attains velocities > 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.