Complex sentence: White Head Island, Gull Rock, Machias Seal Island, and North Rock are part of the larger Grand Manan archipelago; the latter two are about 15 kilometres southwest of Grand Manan Island.
Split into simpler sentences: White Head Island, Gull Rock, Machias Seal Island, and North Rock are part of the larger Grand Manan archipelago. The latter two are about 15 kilometres southwest of Grand Manan Island.