Movie B-2. Extension experiment SchreursG. HänniR. PanienM. VockP. 2019 Movie of lateral variations within the model after 4 cm of extension. Frames 1 through 18 represent serial cross-sections through the domain with a basal viscous layer overlain by brittle layers. Frames 19 through 35 show serial cross-sections through the domain with two viscous layers. The movie clearly portrays the difference in deformation style between domains with and without an interbedded upper viscous layer. The base of the model consists of a compressed assemblage of vertical foam bars (black) and plexiglass bars (dark grey). Width of model is 26.5 cm. Viscous PDMS = dark grey, quartz sand = light to medium grey, corundum sand = light grey.