How were the Okanogan Highlands formed? (1 point) Responses by subduction, which caused huge folds in Earth’s surface by subduction, which caused huge folds in Earth’s surface as a result of retreating glaciers carving great valleys into the earth as a result of retreating glaciers carving great valleys into the earth when molten rock from under the earth approached the surface when molten rock from under the earth approached the surface when the collision of volcanic island chains and ocean rocks formed new earth