SAT Question Khan Academy

Question

"Their predictive power comes from living close to the ocean floor, where they can pick up the sensitive vibrations of tectonic plate movement."

Why is there a comma before where?

Answer 1

Watch out for your 6 "w" words. Who, whom, which, when, where, while typically get commas on the writing section.

Answer 2

There is a comma before "where" because the first part of the sentence is an independent clause. "Where they can pick up the sensitive vibrations etc..." is not an independent clause, which is why the comma has to go before it, to connect it to the independent first half.