sentences:  This tectonic collision forced the basalt formations (and newer sedimentary rock formations that include marine terrace deposits) upward and created the coastal range.Additional basalt flows originated from Eastern Oregon and added to the layers that were uplifted, as the newer Cascade Mountains had not yet been formed.By the Early Oligocene period c. 30 million years ago the current coastline was in place and erosion has continued to shape the range.