In 1963, geologist John Tuzo Wilson explained that the Hawaiian-Emperor seamount chain was created by a hotspot of volcanic activity that stood as the Pacific tectonic plate moved over it. This left a trail of volcanic islands and seamounts. A "bend" or "V" in the chain marks a shift in the movement of the Pacific plate some 47 million years ago, from a northward to a more northwesterly direction. The bend shows how a tectonic plate can shift direction suddenly. A look at the USGS map on the origin of the Hawaiian Islands clearly shows this "spearpoint".