The canyon, formed by years of erosion, was a breathtaking sight to behold.
What best describes the underlined part of this sentence?
restrictive phrase
nonrestrictive phrase
restrictive clause
nonrestrictive clause

The canyon, formed by years of erosion, was a breathtaking sight to behold. Assume that the underlined part is " formed by years of erosion" The underlined clause is best describes is a "nonrestrictive clause." Nonrestrictive clause refers to the clause that when you removed that, the thought of the sentence will not be destroyed.