By left I guess that you mean the western side of the Pacific Basin. There is no longer a spreading ridge on the western side of the Pacific Basin--so the floor is no longer spreading. The seafloor and the paleomagnetic stripes on the seafloor of the Western Pacific were actually created many millions of years ago. In fact, the western side of the Pacific Basin is being subducted--so, the western ocean floor is actually disappearing beneath Japan, New Zealand, etc. <span>In the southeastern part of the Pacific, there is still a spreading ridge, the East Pacific Rise, off of Central and South America. And there are little remnants of spreading ridges just off the the Northwest coast of North America </span> <span>The Atlantic Basin, on the other hand, which has a spreading ridge right down its middle, and has only insignificant subduction along its margin (beneath Caribbean plate), is still getting wider. </span>
