North Island is a collection of several tuff cones in the northern part of Lake Turkana.
Phreatomagmatic material makes up North Island.
The cones are made of lapilli , tuffs and thin basalt flows. A young tuff ring about one km around is in the center of the island. It is inside an older and larger ring. Trachyte lava fills the central ring and flows out on the west side. The same kind of lava is found on the north part of the island too.