The Yukon portion of the northwest trending Northern Cordilleran Volcanic Province includes the youngest volcanoes in Northern Canada. The Fort Selkirk Volcanic Field in central Yukon consists of valley-filling basalt lava flows and cinder cones. Ne Ch'e Ddhawa, a cinder cone to the connection of the Yukon and Pelly rivers formed between 0.8 and one million years ago when this area lied beneath the vast Cordilleran Ice Sheet. The youngest volcano, Volcano Mountain just north of the junction of the Yukon and Pelly rivers, formed in past 10,000 years (Holocene), producing lava flows that remain unvegetated and appear to be only a few hundred years old. However, dating of sediments in a lake impounded by the lava flows indicated that the youngest lava flows could not be younger than mid-Holocene and could be early Holocene or older. Therefore, the most recent activity in the Fort Selkirk volcanic field is unknown. The lava flows from Volcano Mountain are unusual because they originate much deeper in the Earth's mantle than the more common basaltic lava flows found throughout the Yukon and are very uncommon in the geological record. This lava, known as olivine nephelinite, is also unusual because it contains small, angular to rounded fragments of rock called nodules.