Lahars

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.

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.

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 high stratovolcanoes support only about one dozen small glaciers, chiefly in cirques, and numerous patches of perennial snow and ice.