With an age between 6,000 and 7,000 years, Mazama Ash corresponds to the estimated time for Mazama's climactic eruption 6,600 years ago, identified by radiocarbon dating of wood charred by ashflows. Some of the Glacier Peak ash has been found in strata beneath Mazama Ash in Washington state and in eastern Idaho, to the southeast of Glacier Peak. Studies of Glacier Peak Ash deposits suggest that they are older than Mazama Ash, at about 12,000 years old. Glacier Peak Ash has not been found in deposits less than 10,000 years old, and nearly all human artifacts have been found above its deposits, except for a site at Birch Creek where non diagnostic artifacts were discovered beneath Glacier Peak Ash.