Glaciers periodically covered Mount Mazama's flanks and carved out the U-shaped valleys such as Munson Valley and Kerr Notch.
(Glaciers; covered; Mount Mazama's flanks; T:periodically) (Glaciers; carved out; the U-shaped valleys such as Munson Valley and Kerr Notch; T:periodically)
Glaciers Glaciers
covered carved out
Mount Mazama's flanks T:periodically
the U-shaped valleys such as Munson Valley and Kerr Notch T:periodically