Tangjiashan quake lake

The M7.9 Sichuan earthquake of May 12th triggered a massive landslide that created a lake at Tangjiashan.

Landslide created dams are notoriously unstable, and the Chinese authorities have been trying to limit the possible damage from an uncontrolled breach of the Tangjiashan dam by cutting a sluice to evacuate the ever rising water.

It seems now that these efforts have been in vain... See Dave Petely's great series of posts on the subject.

[Thanks to Andrew and Chris for useful links into this subject.]