sentences:  The bulk of this island is made up of a thick stack of olivine basalt, olivine trachybasalt, and nepheline basalt lava flows.Overlying these lava flows is a layer of friable volcanic ash and tuff that is capped by a thick basalt lava flow.The total thickness of volcanic rocks exposed within Zhokhov Island is about 400 meters 
  
  Rush/grass, forb, cryptogam tundra covers the Zhokhov Island.