This sentence can be classified as a nonrestrictive phrase based on its composition and function in the sentence.
What is the difference between a clause and a phrase?
Clauses often include a subject and a verb while phrases do not. Based on this the underlined part is a phrase.
What is nonrestrictive?
This word is used when an element in a sentence is not essential to its meaning. This occurs with "formed by..." because this is only an extra detail about the canyon.
Learn more about clauses in: https://brainly.com/question/2669118
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