Assertion: range's mountain | /r/CapableOf | block their westward course
Facets:
value: to the ancient sea
type: TRANSITIVE-OBJECT
Source sentences:
text: When the mountains were thrust up, blocking their westward course to the ancient sea that once covered the American Midwest, these old rivers cut out their own routes, creating those spectacular canyons, gorges, and “narrows” that are part of Appalachian scenery.