The valley along the fault

The Idrija fault is a an active fault crossing Slovenia for more than 100 km in a NW-SE direction, which is responsible of several important geological features in the country. Among them, we can mention the former-active Mercury mine of Idrija which is registered as a Unesco World Heritage site since 2012. Another example put in evidence the impact of this fault on the regional hydrology: due to its strike-slip movement, this fault generated a set of four sucessive poljes belonging to the catchment of the Ljubljanica River. These large flat depressions are regularly flooded and can form several meters high temporary lakes that can last for months. The largest of them is named Cerknisko jezero (Cerknica Lake) and reaches a surface of more than 20km2.