Lar dam located about 84 kilometers northeast of Tehran has been established over the Lar river, one of the main branches of Haraz river, to supply part of the required water of Tehran.The course leading to this location is through Haraz road separated from main road in Polur and extending 10 kilometers toward northwest as far as the dam site.
This embankment dam is of an 1150-meter-long, 8-meter-wide and 105-meter- high crest. The abutments of the dam are situated on two different formations. The left one on Damavand volcanic flows as well as part of ancient lake sediments and the right one on the Lar lime formation (Late Jurassic).
Tectonic stresses influencing both abutment rocks and dam lake have caused a crushed zone and abundant discontinuities that may be from breccia zones kind, different types of faults or countless joints or cracks. Intrusion of downgoing waters into the mentioned discontinuities has had an important role in solving carbonate rocks and creating solution caverns and cavities; therefore, water-escape is one of the major problems of this dam. Since the remedy seeking in this respect has been necessary but not sufficient, there are still several karst springs in the downstream toe of the dam.
Damavand volcano as the symbolic peak of Iran Plataue is the most outstanding Quaternary stratified volcano of Iran of which summit is 5670 meters high of the sea level and 1600 to 2000 meters high of the surrounding lands.The whole mountain slope has been covered by continual lava flows flowing down over and over from main crater or secondary cones and also by pyroclastic matters. The crater diameter is about 400 meters.The central part of the crater around which there are some fumaroles making the surrounding lands yellow is coated by an ice lake.
The basic rocks, especially seen in Polur and Tineh, are the oldest flows of Damavand.Most of the rocks of this volcano are from intermediate type and just a few of them from acidic type having lava and pyroclastic outcrops. The existing documentary data indicates the latest activity of Damavand belongs to 38500 years ago.
A view of Damavand from Imamzadeh Hashem pass.