The islands were formed about four to five million years ago by underwater volcanoes that erupted and rose above the ocean's surface.
(The islands; were formed; T:about four to five million years ago; by underwater volcanoes) (underwater volcanoes; erupted; ) (underwater volcanoes; rose; L:above the ocean's surface)
The islands underwater volcanoes underwater volcanoes
were formed erupted rose
T:about four to five million years ago by underwater volcanoes
L:above the ocean's surface