An Australian naval vessel, also containing relief supplies, was due to depart on Wednesday.
Ever since new land rose above the water surface in 2015 and joined two existing islands, Garvin and an international team of researchers have been monitoring changes there.
A second undersea cable that connects the islands within Tonga also appeared to have been severed, Fonua said.
He added that it was unclear when it would be safe for a ship to venture near the undersea volcano to undertake the work.