Hazards

Three Sisters is a potentially active volcanic center that lies close to rapidly growing communities and resort areas in Central Oregon.

Volcanoes in the Three Sisters region have erupted a wide variety of magma types, therefore the shape, size, and impact of future lava flows could vary greatly.

Eruptions from any volcano in the Three Sisters region, as well as from more distant volcanoes in the Cascade Range, are sources of potential tephra fall in Central Oregon communities.

Pyroclastic flows can form in two ways: from the collapse of a tephra plume during an explosive eruption or from the collapse of the front of a steep lava flow or dome on a volcano's slope.

South, Middle, and North Sister, as well as Broken Top are high, steep-sided peaks that could produce debris avalanches.

Explosive eruptions or large debris avalanches on the Three Sisters can generate lahars of sufficient volume to travel tens of kilometers from source areas.

The Three Sisters region has hosted volcanic eruptions for hundreds of thousands of years, and future eruptions are a certainty.