Question

is the group of words in bold a phrase or a clause?
usually the result of earthquakes or volcanic activity, tsunamis are enormous ocean waves that can devastate docked ships; meanwhile, ships at sea may not even detect the massive waves.
phrase clause

Explanation:

A clause contains a subject and a predicate. "Tsunamis are enormous ocean waves" has a subject "tsunamis" and a predicate "are enormous ocean waves". A phrase does not have a subject - predicate relationship.

Answer:

clause