Are neighboring ridges on different tectonic plates which have similar seismic characteristics. ‘Based on similar seismic velocity gradients of the lavas of the Carnegie, Cocos and Malpelos Ridges the
re is evidence that the hotspot activity has been the result of a single long mantle melt rather than multiple periods of activity and dormancy.’ [Wikipedia]
A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure. The mass of pyroclastics is normally of very high temperature and move
s rapidly down the slopes or even along a level surface.