Isn’t methane in crystal form at those pressures and temperatures?
I glanced at the article. I didn’t see anything about the depth of these vents. If deep enough you are right!
I remember seeing a pie chart about man-made petroleum spills in the oceans vs natural petroleum venting. These are spills from oil platforms, tanker mishaps etc. Bottom line, man-made spills very insignificant compared to what mother nature leaks into the ocean. Also at the bottom of the graphic was a statement pointing out that pie chart area for the natural leakage was a minimum estimate. The true amount is probably much much higher and dynamic!