Kleifarvatn is the largest lake on the Reykjanes peninsula in Iceland, situated in the southern part of the peninsula on the fissure zone of the Mid-Atlantic Ridge. The lake can be reached via a track, and there are two areas with high temperature that can be found not far from it: Seltún/Krýsuvík and another to the east. The lake's greatest depth is 97 m. After the big earthquake in 2000, the lake began to diminish, and 20% of its surface has since disappeared.
The cracks that opened up in the earthquake have since then slowly filled again and by
2008 the lake had regained its previous surface level.
Map kleifarvatn see here