The deputy secretary of Tonga's Ministry of Lands, Taaniela Kula, said Tongan geologists visited the island late last year with scientists from NASA.
"There are some speculation on the source of this vegetation. Either from growing from the island or from the birds waste dumping on the sides.
"Because the island is full of a variety of birds, sea birds, and they nest in the area and they produce more birds around the crater and also they reside in the gullys of the volcano."
