The Wells Gray-Clearwater volcanic field began forming approximately 3,500,000 years ago and has grown steadily since then. The tectonic causes of the volcanism that have produced the Wells Gray-Clearwater volcanic field are not yet clear and are therefore a matter of ongoing research. It is approximately inland from the north-south trending Garibaldi Volcanic Belt and is along-strike from the Nootka Fault on the British Columbia Coast, which has been subducting under the North American Plate at the Cascadia subduction zone. The Wells Gray volcanics are mostly alkali olivine basalt, with some lava flows comprising mantle xenoliths. Basalts of the Wells Gray-Clearwater volcanic field have been considered to be the easternmost expression of the Anahim Volcanic Belt. However, its relationship is unknown because the age-location trend does not reach into the Wells Gray-Clearwater area, and the Wells Gray-Clearwater volcanic field is not along trend with the Anahim Volcanic Belt. The Wells Gray volcanics were thought to have formed by crustal thinning and the existence of crustal penetrating structures.