Strike-slip motion and double ridge formation on Europa

[1] There is abundant observational evidence for strike-slip displacement on the surface of Europa. Strike-slip motion between crustal blocks produces shear heating and an increase in temperature. We model the shear heating within the ice crust using a two-dimensional, finite difference formulation, with a near-surface brittle layer of constant specified thickness and a Newtonian ductile layer beneath. We obtain a maximum temperature anomaly of 66 K for a brittle layer thickness of 2 km and shear velocity of 6 10 7 m s . Such a velocity is appropriate for diurnal (85 hour) tidal motion. The local increase in temperature may cause 100 m uplift around the shear zone through thermal buoyancy. The stresses required to produce velocities of order 10 7 m s 1 are similar to estimates for present-day tidal stresses on Europa (10–10 Pa). Brittle layer thicknesses >2 km are unlikely to persist at active shear zones because of the effect of shear heating. Shear velocities greater than or equal to 10 6 m s 1 will give rise to melting at shallow depths. The removal of material by downwards percolation of meltwater may cause surface collapse along the shear zone; inward motion, leading to compression, may also result. The combination of thermally or compression-induced uplift and melt-related collapse may be responsible for the pervasive double ridges seen on Europa’s surface.