How long have seamounts been around to be flattened so much? Do seamounts still erupt?
Some seamounts are forming through volcanic eruptions right now. A good example is Loihi, the newest addition to the Hawaiian seamount chain. If you follow the Hawaiian chain westward, you will see older and older seamounts. While Loihi has not yet grown above sea level, the state of Hawaii is made up of seamounts that have become islands. With three pieces of information you can calculate the age of the oldest Hawaiian island: the Pacific plate is moving over the Hawaiian hot spot at a relative speed of about 30 kilometers per million years (My); the hot spot is basically underneath Loihi right now; the distance from Loihi to the oldest island is about 900 km. So, the oldest island is about (900 km / 30 km/My = ) 30 million years old. The Hawaiian chain continues west for about ~2100 kilometers and then connects to the Emperor seamount chain that extends ~2100 kilometers, all the way to the Aleutian trench. Assuming the same relative speed has been maintained during their formation, t
