Volcanic activity has occurred in parts of Iran since the Cretaceous period. During the Eocene and Oligocene epochs, volcanic activity reached its maximum, with thick pyroclastic layers being deposited in central Iran and the Alborz mountains. The area around Taftan volcano belongs to a tectonic zone which is variously referred to as the Sistan suture or the Zabul-Baloch zone. There, after a previous episode of rifting and subsequent formation of an ocean, the Neh and Lut tectonic blocks collided during the Eocene epoch after a subduction episode that commenced in the Maastrichtian age.