Pacific Northwest Research Station

Chaiten Photoessay

Rio Los Gigios Bridge

Rio Los Gigios, a small stream flowing 2 kilometers (1.2 miles) from Chaitén’s caldera rim to this bridge, experienced many effects of the eruption. The adjacent forest was scorched by a blast originating from the volcano’s eruption column that sent a hot sand- and gravel-charged surge downhill, snapping and toppling trees and blasting off their limbs. This blast blanketed the forest with about 10 cm of sand and gravel deposits. Debris flows and sediment transported by the stream from the blast zone greatly modified the stream channel. Several small landslides high on Chaitén’s flanks, triggered by the blast or heavy rains in May 2008, moved soil and trees from hillslopes into the stream, creating small dams that temporarily trapped water and sediment before bursting and unleashing a torrent of water, sediment, and large pieces of wood. The resulting debris flows crashed into Rio Los Gigios bridge, bending the railing on the upstream side, before continuing on for as much as several hundred meters downstream. This stream has been transporting a great deal of sediment since the eruption, excavating the channel down to a bed of boulders. Some channel clearing was carried out with heavy equipment shortly after the eruption commenced. Vegetation cover was dramatically reduced here, yet surviving plants are sprouting and new plants are colonizing the area. Nonetheless, it will take several decades to centuries for the area to support forests typical of those present before the eruption.

Photo Gallery

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