After the last major climax eruption 630,000 years ago until about 70,000 years ago, Yellowstone Caldera was nearly filled in with periodic eruptions of rhyolitic lavas (example at Obsidian Cliffs and basaltic lavas (example at Sheepeaters Cliff). But 150,000 years ago the floor of the plateau began to bulge up again. Two areas in particular at the foci of the elliptically shaped caldera are rising faster than the rest of the plateau. This differential in uplift has created two resurgent domes (Sour Creek dome and Mallard Lake dome which are uplifting at 15 millimeters a year while the rest of the caldera area of the plateau is uplifting at 12.5 millimeters a year. A report in mid December 2006 indicates that two of Yellowstone’s dome areas have been rising at an increased rate since 2004. The Mallard Lake Dome and the Sour Creek Dome have risen at a rate of 4 to 6 cm/yr since 2004
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