Seward Park peninsula is a glacially formed drumlin/terminal moraine

Seward Park projects into Lake Washington as a distinct peninsula that is a glacial landform-part of a terminal moraine or drumlin deposited by the Vashon Glaciation. The park's elevated ridge and soils differ from surrounding shorelines because they are composed of glacial till and deposited sediments. Seward Park's topography and old-growth forest patches reflect its origin as a remnant glacial feature within the urban landscape.