Delta (dashed yellow line) formed by the Sandy River projecting int...
Detailed Description
The Sandy River flows through the axis of the delta and its confluence with the Columbia is visible in forested area to right of Troutdale Airport (black strip to right of Interstate 84). Delta is formed chiefly of lahar deposits and related deposits from Mount Hood generated during two eruptive periods of past 1,500 years. These deposits also form parts of islands downstream from the delta.