Map of the Northwestern United States showing major volcanic features associated with the Yellowstone mantle plume

Map of the Northwestern United States showing major volcanic features associated with the mantle plume currently underneath Yellowstone caldera.  Colors indicate general basaltic (blues) versus rhyolitic (reds) compositions, with shades indicating age (darker shades are older).  Rough outlines of calderas that formed due to the Yellowstone hotspot are given, with numbers indicating approximate ages in millions of years.