Hawaii's Oahu Used To Be a Bigger Island

sciencehabit (1205606) writes "The two volcanoes long thought to have formed the Hawaiian island of Oahu had a head start: They grew on top of an older volcano that's now submerged northwest of the island and partially covered by it, new research suggests. Tests indicate that the long-lost peak—now dubbed Kaena volcano—grew from the sea floor and broke through the ocean's surface about 3.5 million years ago, eventually reaching a height of about 1000 meters above sea level before it began sinking back into the sea. At its largest, ancient Oahu would have measured about 1900 square kilometers (about 20% larger than modern-day Oahu) or larger. Over the course of its lifetime, Kaena volcano spilled between 20,000 and 27,000 cubic kilometers of molten rock, the researchers estimate. When Kaena volcano became largely extinct isn't clear."

This is news?

[Drathos]

My first reaction was "Um.. Duh?"

I learned this in middle school, I believe. The Hawaiian Islands are a chain that's formed by the movement of the Pacific Plate across a hot spot. As it passes over, a volcano builds up and builds up, eventually forming an island that keeps growing as long as the vent stays over the hot spot. Eventually, it will move on and start eroding, while another volcano starts up at the ocean floor. All of the Hawaiian Islands except for Hawai'i (The Big Island) are currently shrinking, while Hawai'i is still growing. If you look at charts of the Pacific Ocean's floor, you can see a long chain going all the way to the subduction zone at the Aleutian Trench.