|
The Emperor Seamounts are a chain of seamounts (submerged volcanic mountains) extending from the northwestern Hawaiian Islands (see Kure and Midway atolls) in a northwesterly direction until approximately 170ยบ east longitude where they trend abruptly northward towards the tip of the Aleutian Islands and the Kamchatka Peninsula. The chain's name reflects the naming of many of the individual volcanoes for legendary and historic emperors of Japan (Yuryaku, Kimmei, Nintoku and Suiko are examples). They were named by Robert S. Dietz in 1954. The Emperors are the submerged remnants of volcanic islands of what we now call the Hawaiian Islands and are part of the Hawaiian-Emperor seamount chain. The age and depth of the ancient volcanoes increases toward the northern tip of the chain. Most of the older Emperors are flat topped seamounts (or guyots) showing evidence of once having been reef encircled, high islands and then coral atolls. The change in trend of the seamounts has been regarded as evidence of a directional change of the Pacific Plate some 40 million years ago as it moved over the "fixed" hot spot that created each volcanic island that later subsided to a seamount. The plate is being subducted at the trenches bordering the North Pacific rim. One explanation of the northward trend of the Emperors has been that they represent a hard plate portion that distorted the trench system of the North Pacific forming an apex seen at the Kuril-Aleutian Trench junction. A look at the USGS map on the Origin of the Hawaiian Islands clearly shows this "spearpoint". However, how or why such a change in direction occurred has generally defied explanation. Recent research shows that the hot spot itself may be moving southward (Tarduno et al., 2003). Yet more recently published argon-argon ages of rocks from volcanoes of the southern and central Emperor chain better establish the age at which the bend formed. Sharp and Clague (2006) determined that the bend initiated at about 50 million years ago, and the bending continued until about 42 million years ago. They also concluded that the bend formed because of the "traditional" reason -- a change in the direction of motion of the Pacific plate. They attribute the change in direction to the onset of subduction in some of the island arcs of the western Pacific. The Seamounts include: (*)
See also | ||||||||
|
| |||||||||
 |
|
| |