Eco Region Assessment 30. Geologically, this ecoregion is made up of glacial till and outwash with some lacustrine deposits. The climate is Mediterranean with warm, dry summers and mild, wet winters. The drier areas are caused by rain-shadows from the Olympic Mountains resulting in the development of natural grassland and savanna communities. The sound itself and the rivers that flow into it are important ecological and cultural features of this ecoregion.
Flooding is the major natural disturbance event today.