Areas in blue or purple show regions at risk of local volcanic activity, including lava flows, ashfalls, lahars (volcanic mudflows) and debris avalanches.

Areas in pink show regions at risk of receiving 5 cm or more of ashfall from large or very large explosive eruptions, originating at the volcanic centers shown in blue. These projected ashfall extents are based on observed ashfall distributions from an eruption ("large") of Mt. St. Helens that took place 3,400 years ago, and the eruption of Mt. Mazama ("very large") that formed Crater Lake, OR, 6,800 years ago.