Ka ‘Āina:  The Land

Nineteen miles off the coast of the Big Island of Hawai‘i an island is being born.  Named Lō‘ihi, it will rise above the ocean waters sometime between 40,000 and 50,000 years from now, becoming the youngest island and the latest in a long line of island “births.”  Remarkably, this birth of the Hawaiian Islands is ongoing and has been occuring for at least 80 million years.  This unfolding creation is the result of a localized “hot spot” of volcanic activity on the floor of the Pacific Ocean generated by a plume of magma rising from the border of the Earth’s core.

Over the millennia this stationary plume has created every island between Hawai‘i Island in the southeast of the chain to Kure Atoll in the northwest and even beyond to the line of submerged Emperor Seamounts.  As each island is born, however, it is also pulled away from the hot spot by the slow-moving Pacific Plate upon which it sits.  This tectonic plate slides to the northwest at a rate of 3-4 inches per year, dragging each new island further and further from its magma source until it is separated completely.  As it continues its long outward journey the force of erosion prevails and slowly the island disappears beneath the sea.  What is its ultimate fate?  To reach the Aleutian Trench and be subducted and melted under the Eurasian Plate.  The oldest seamount thus poised is estimated at 75-80 million years of age.  Who knows how many older islands have already disappeared?

The Life of O‘ahu Island

O‘ahu, one of the oldest of the eight main Hawaiian Islands, is yet still young in the entire island chain.  Composed of two volcanoes that reached the surface of the ocean roughly 4 million and 2.5 million years ago, its last activity occurred perhaps only 6,000 years ago.  While it has been disconnected from the hot spot currently under the Big Island, deep within its volcanoes it still contains pockets of fluid magma.  If this magma comes in contact with underground waters the steam created can force small, localized eruptions, the most famous of which is our current Diamond Head Crater.  Eventually, however, O‘ahu will disappear beneath the waves and perch for rebirth on the edge of the subduction trench.

In the meantime, for those of us living today, O‘ahu provides one of the most spectacular island settings in the world.  Thanks to a million years of erosion O‘ahu now offers spectacular, plunging mountain cliffs, beautiful white sand beaches and lush, rainforested valleys.  In her declining youth O‘ahu is more beautiful than ever.