These glaciers formed the narrow valleys, giving them their U shape.
(These glaciers; formed; the narrow valleys; giving them their U shape) Context(These glaciers formed,List([0, 21))):(These glaciers; formed the narrow valleys giving; them; their U shape)
These glaciers formed,List([0, 21))
These glaciers These glaciers
formed formed the narrow valleys giving
the narrow valleys giving them their U shape
them their U shape