Rifts in Spreading Wax Layers

Abstract

We report experimental results on the rift formation between two freezing wax plates. The plates were pulled apart with constant velocity, while floating on the melt, in a way akin to the tectonic plates of the earth's crust. At slow spreading rates, a rift, initially perpendicular to the spreading direction, was found to be stable, while above a critical spreading rate a "spiky" rift with fracture zones almost parallel to the spreading direction developed. At yet higher spreading rates a second transition from the spiky rift to a zig-zag pattern occurred. In this regime the rift can be characterized by a single angle which was found to be dependent on the spreading rate. We show that the oblique spreading angles agree with a simple geometrical model. The coarsening of the zig-zag pattern over time and the three-dimensional structure of the solidified crust are also discussed.Comment: 4 pages, Postscript fil

Laboratory Studies of Mantle Convection

“…This wax gave birth to the different regimes shown in Figure 55 (Ragnarsson et al, 1996), but the orthogonal transform faults observed by Brune (1972, 1975) were never observed. In the first case (Shell Wax 120), the solid layer could be divided in two regions because the paraffin wax undergoes a solid-solid phase transition: a colder phase, hard and brittle, where strain is mostly accomodated by crack formation during extension; and a warmer ductile phase, where strain is accomodated primarily by viscous flow.…”

“…Ridge morphology has been studied using paraffin wax as an analog mantle material: solid wax simulates brittle mantle and molten material simulates the region that deforms as a viscous fluid Brune, 1972, 1975;Ragnarsson et al, 1996). The molten wax was frozen at the surface by a flow of cold air.…”

“…Oldenburg and Brune (1972) first observed that a straight rift initially perpendicular to the pulling direction evolved into a pattern consisting of straight segments interrupted by faults orthogonal to the rift and parallel to the pulling direction (Figure 54). Ragnarsson et al (1996) and Bodenschatz et al (1997) studied the phase diagram in more detail, investigating the rift structure as a function of the pulling speed for two different waxes. Ragnarsson et al (1996) and Bodenschatz et al (1997) studied the phase diagram in more detail, investigating the rift structure as a function of the pulling speed for two different waxes.…”

Role of random thermal perturbations in the magmatic segmentation of mid-oceanic ridges: Insights from numerical simulations

“…Experimental and theoretical modeling of the MOR mechanism has thus recently gained its wide acceptance as an effective alternative approach. Analog models have been used extensively, utilizing mainly wax of different variety (Katz et al, 2005;O'bryan et al, 1975;Oldenburg and Brune, 1975;Ragnarsson et al, 1996) and other materials, such as sand-silicone (Dauteuil et al, 2002), sand-PDMS (Marques et al, 2007), and silicone (Tentler and Acocell, 2010). Unfortunately, these analog experiments did not couple the process of magmatic upwelling with the segmentation mechanism.…”

Zig-zag wall lattice in a nematic liquid crystal with an in-plane switching configuration

“…These walls, subjected to electric and magnetic fields, can exhibit a zig-zag instability [13][14][15]. This type of instability is a universal phenomenon, which is observed in various * iandrade@ing.uchile.cl † marcel@dfi.uchile.cl ‡ vodent@ing.uchile.cl physical contexts such as in microwrinkle grooves [16], gas discharge systems [17], crystals growth [18], rifts in the spreading wax layer [19], the chevron layer structure of smectic liquid crystals [20], and nematic liquid crystal samples subjected to a temperature gradient [21] or a confinement configuration [22].…”