Experiment DS-15 was conducted under basic conditions of pure stress,
with silicone layer thickness of 1.5 cm and sand layer thickness of 0.5
cm. Rate of extension was 1 cm/hour, and the experiment lasted 10 hours.
The deformation along the central gection of the sand layer was approximately
45% of the total displacement, the remainder took place along the boundaries
of the experiment box. Two irregularities affected the results of the experiment.
First, due to a mechanical difficulty a counter clockwise rotation of 8°
was introduced inadvertantly into the experiment, adding slight sinistral
shear to the extension. Second, several air bubbles remained embedded in
the silicone layer. As the experiment progressed the bubbles were released
slowly, forming volcano-like structures. Please not that the initial site
of rifting occurs at such a "volcano". Note the linear propagation
of the rift, and the ascent of the silicone along the rift axis.
