Erosion has since exposed part of the seamount in the northern sector of the Caldera. Every Emperor seamount is a dead volcano. Cortes Bank is a shallow seamount (a barely submerged island) in the North Pacific Ocean. Erosion then weathers the volcano until it again becomes a seamount. Overfishing is a serious threat to seamount ecological welfare. The only active volcano is the Macdonald seamount (40m depth). The final stages of eruption cap the seamount in alkalic flows. A series of ridges and seamount chains produced by hotspots pass over the Indian Ocean. It is an erupting seamount that now reaches approximately below the surface of the ocean. The seamount was formed in the late Cretaceous. By 1967, over of soundings and dozens of samples from the seamount had been collected. The largest seamount has an area of and it occurs in the North Pacific. On its northern side is the exposed remains of the original seamount. The rate along the Emperor seamount chain averaged about per year. The collision with the seamount was so severe that "San Francisco" nearly sank.