The second unit formed several volcanic cones south and southwest of the lake, consisting of trachyandesite.

[7] Eruptions commenced about 9.23 million years ago according to potassium-argon dating; thermoluminescence dating has yielded an age of 67,000 years for the most recent eruptions[5] and Heishibeihu is considered to be the most recently active volcano in the Tibetan Plateau.

[3] Seismic tomography has identified mantle upwelling below the volcanic field,[8] which is linked to the subduction of the Indian Plate.

[11] Volcanic fields in the area include Kangxiwar, Dahongliutan, Quanshuigou and Heishibeihu in the south and north Pulu, east Pulu and Ashikule volcanic field in the south.

They feature mainly lava flows forming terraces and platforms, with craters and pyroclastics uncommon.