  Europa's surface exhibits morphological features which, associated with a low
crater density, might be interpreted to have formed as a result of recent
cryovolcanic activity. In particular, the morphology of smooth deposits
covering parts of the surface, and their relationship to the surrounding
terrains, suggest that they result from liquid extrusions. Furthermore, recent
literature suggests that the emplacement of liquid-related features, such as
double ridges, lenticulae and chaos could result from the presence of liquid
reservoirs beneath the surface. We model the ascent of liquid water through a
fracture or a pipe-like conduit from a subsurface reservoir to
Europa\textquoteright s surface and calculate the eruption time-scale and the
total volume extruded during the eruption, as a function of the reservoir
volume and depth. We also estimate the freezing time of a subsurface reservoir
necessary to trigger an eruption. Our model is derived for pure liquid water
and for a briny mixture outlined by Kargel (1991): 81 wt% H$_{2}$O + 16 wt%
MgSO$_{4}$ + 3 wt% Na$_{2}$SO$_{4}$. Considering compositional data for salt
impurities for Europa, we discuss the effect of MgSO$_{4}$ and Na$_{2}$SO$_{4}$
on the cryomagma freezing time-scale and ascent. For plausible reservoir
volumes and depths in the range of $\mathrm{10^{6}\:m^{3}\leq
V\leq10^{10}\:m^{3}}$ and $\mathrm{1\:km\leq H\leq10\:km}$ respectively, the
total extruded cryolava volume ranges from $10^{3}\,\mathrm{m^{3}}$ to
$10^{8}\,\mathrm{m^{3}}$ and the duration of the eruptions varies from few
minutes to few tens of hours. The freezing time-scale of the cryomagma
reservoirs varies with cryomagma composition and the temperature gradient in
the ice shell: from a few days to a thousand years for pure water cryomagma,
and from a few months to a 10$^{4}$ years for briny cryomagma.
