Early research described Lake Erçek as having been formed through volcanic activity; however, recent research indicates that it is a
tectonic lake. The lake's basin was formed by north–south trending faults during the
Upper Pleistocene. It appears that the lake did not rise much above its current level during the Upper Pleistocene and
Holocene, based on examination and
radiocarbon dating of
core samples of lake sediments. Research suggests the lake did not overflow its basin during this period. The lake's main inflow is from the Memedik Çayı (also known as the Büyükçaylak Deresi), which enters via a broad fan at the west of the lake. The Karasu river, which rises along the Iranian border, passes within of the northwest shore of the lake and is separated only by a low ridge, but it does not enter the lake and continues west to enter
Lake Van northwest of the city of
Van. ==Natural history==