Hawaii is the biggest island in the Hawaiian archipelago, but it hasn't always been that way. The four modern islands of Maui, Moloka'i, Lana'i and Kaho'olawe once were all connected in one gigantic land mass that scientists have dubbed Maui Nui (which in the Hawaiian language means "big Maui"). At its peak size 1.2 million years ago, Maui Nui stretched for 5,640 square miles (14,600 square kilometers), making it about 50 percent bigger than the island of Hawaii is today [source: Hawaii Volcano Observatory].
Maui Nui was a land of multiple volcanoes, created by spewing vast amounts of lava from Earth's upper mantle. But what made the island so big also contributed to its demise. As the volcanoes gradually stopped building up the land, the weight of all that lava eventually caused the oceanic crust to buckle and subside. That caused the connections, or saddles, between the volcanoes eventually to sink beneath the water, which gradually split the volcanoes into separate islands.
But even though Maui Nui no longer exists as a single island, its presence is still felt. Species spread across its land mass before it separated, so the four islands that resulted have very similar flora and fauna [source: Hawaii Volcano Observatory].