field, Orevada rift, McDermitt, Nevada/ Oregon (five overlapping and nested calderas; satellitic to these are two additional calderas), : Trout Creek Mountains, East of the Pueblo Mountains, Whitehorse Caldera (size: 15 km wide), Oregon; 15 Ma; of Whitehorse Creek Tuff. Jordan Meadow Caldera, (size: 10–15 km wide); 15.6 Ma; Longridge Tuff member 2–3. Longridge Caldera, (size: 33 km wide); 15.6 Ma; Longridge Tuff member 5. Calavera Caldera, (size: 17 km wide); 15.7 Ma; of Double H Tuff. Trout Creek Mountains, Pueblo Caldera (size: 20 x 10 km), Oregon; 15.8 Ma; of Trout Creek Mountains Tuff. Hoppin Peaks Caldera, 16 Ma; Hoppin Peaks Tuff. Washburn Caldera, (size: 30 x 25 km wide), Oregon; 16.548 Ma; of Oregon Canyon Tuff. Yellowstone hotspot (?), Lake Owyhee volcanic field; 15.0 to 15.5 Ma. Yellowstone hotspot (?), Northwest Nevada volcanic field, Virgin Valley, High Rock, Hog Ranch, and unnamed calderas; West of the Pine Forest Range, Nevada; 15.5 to 16.5 Ma; Tuffs: Idaho Canyon, Ashdown, Summit Lake, and Soldier Meadow. Columbia River Basalt Province: Yellowstone hotspot sets off a huge pulse of volcanic activity, the first eruptions were near the Oregon-Idaho-Washington border. Columbia River and Steens flood basalts, Pueblo, and Malheur Gorge-region, Pueblo Mountains, Steens Mountain, Washington, Oregon, and Idaho; most vigorous eruptions were from 14 to 17 Ma; of lava. Columbia River flood basalts, Steens flood basalts, Crescent volcanics, Olympic Peninsula/ southern Vancouver Island, 50–60 Ma. Siletz River Volcanics, Oregon Coast Range, a sequence of basaltic pillow lavas. Carmacks Group, Yukon, , 70 Ma. Notes Harney Basin (Devine Canyon Tuff), McDermitt volcanic field, Owyhee-Humboldt volcanic field, Lake Owyhee volcanic field (or Jordan Valley volcanic field, Lake Owyhee), Jordan Craters, Santa Rosa – Calico volcanic field, Hawkes Valley – Lone Mountain volcanic field, Northwest Nevada volcanic field, Juniper Mountain caldera complex, and Silver City – Delamar caldera complex (Silver City, Idaho) are nested in one area. Geologic landmarks of the area: Steens Mountain, Northern Nevada Rift, Midas Trough, Santa Rosa Mountains, Bull Run – Tuscarora Mountains, Owyhee Mountains, Oregon-Idaho Graben, and western Snake River Plain. Other manifestations of the Yellowstone hotspot: Rexburg Volcanic Field (4.3 Ma), West of Rexburg, Idaho; Henry's Lake Volcanism (1.3 Ma), Henry's Lake; Blackfoot Volcanic Field (3 Ma), Northwest of Soda Springs, Idaho; Gem Valley Volcanic Field (600 to 50 ka), near Grace, Idaho. The initial volcanism is part of the Basin and Range Province and the Oregon-Idaho graben (15.0 to