A zone of small-volume basaltic lava flow eruptions about 150 km inland fromand running parallel to the Garibaldi volcanic belt. Activity in this area is thought to be a result of extension of the crust behind the coastal subduction zone, a common phenomenon worldwide termed "back-arc extension volcanism". Chilcotin eruptions happened mainly 6-10 million years ago and 2-3 million years ago in the early stages of Garibaldi belt activity. In addition there have been a few eruptions in the Pleistocene (0.01 to 1.6 million years ago). The volcano maps show only the Chilcotin eruptions that are Pliocene and younger (younger than 5.3 million years).