But the Purgatoire River flowing east from the Rocky Mountains has created an expansive valley traversed by a profusion of canyons and sub-canyons.
(the Purgatoire River flowing east from the Rocky Mountains; has created; an expansive valley traversed by a profusion of canyons and sub-canyons) (an expansive valley; traversed; by a profusion of canyons and sub-canyons)
the Purgatoire River flowing east from the Rocky Mountains an expansive valley
has created traversed
an expansive valley traversed by a profusion of canyons and sub-canyons
by a profusion of canyons and sub-canyons