 Considerable recent uplift, accompanied by rapid erosion, has reduced once vast areas of upper Tertiary volcanic rocks to small isolated remnants.Although no eruptions have occurred in the Yukon portion of the Wrangell Belt for the past five million years, two large (VEI-6) explosive eruptions from Mount Churchill west of the Alaska-Yukon border, created the White River Ash deposit.This volcanic ash deposit is estimated 1,890 and 1,250 years old, covering more than of northwestern Canada and adjacent eastern Alaska.