Mazama Ash

The ash was ejected from Mount Mazama, a volcano in south-central Oregon, during its climactic eruption about 7640 ± 20[4] years ago when Crater Lake was formed by caldera collapse.

[5] Because it was deposited throughout a wide area at a known time, the Mazama Ash is an important marker bed for paleoclimatology, paleoecology, and archaeology, as well as for Quaternary geology and stratigraphic correlation.

[11] The Mazama ash spread over an area of at least 900,000 km2 (350,000 sq mi) in the northern Great Plains, where it is most commonly preserved within peat, alluvial, lacustrine, and aeolian sediments.

In Canada, deposits of Mazama Ash several centimeters thick are commonly present in southern areas of British Columbia,[14] Alberta, and Saskatchewan.

[12] In southern Alberta, about 1000 kilometers (about 600 miles) northeast of the eruption site, the Mazama Ash is typically found as a white band located several metres below the present ground surface.

[21] Comparison with the effects of the Mount St. Helens eruption of 1980 indicates that the Mazama Ash would have covered the landscape in a blanket up to 15 cm (6 in) thick, coating vegetation and clogging watercourses throughout the ashfall area.