A broad region with numerous formerly subglacial volcanic cones known as tuyas forms the Tuya Volcanic Field near Tuya Lake and a broad area to the N. Although tuyas, the products of Pleistocene subglacial eruptions, are perhaps better known in Iceland, these predominantly flat-topped basaltic table mountains derive their name from the Tuya region in the Cassiar Mountains and Tanzilla Plateau area of northern British Columbia. Tuya Butte itself, immediately N of Tuya Lake, has no summit crater or obvious vent, suggesting fissure-fed eruptions, although several indications suggest a vent location near a large cirque on the N face. Other tuyas lie in the High Tuya Lake, Iverson Creek, Rancheria River, and Klinkit Lake areas. Several small subaerial shield volcanoes, and postglacial lapilli cones and lava flows have been reported in this area. At least one of these, Grabrielse Cone near the headwaters of Iverson Creek, is of Holocene age.