Rough versus smooth topography along oceanic hotspot tracks: Observations and scaling analysis

Some hotspot tracks are topographically smooth and broad (Nazca, Carnegie/Cocos/Galápagos, Walvis, Iceland), while others are rough and discontinuous (Easter/Sala y Gomez, Tristan‐Gough, Louisville, St. Helena, Hawaiian‐Emperor). Smooth topography occurs when the lithospheric age at emplacement is young, favoring intrusive magmatism, whereas rough topography is due to isolated volcanic edifices constructed on older/thicker lithosphere. The main controls on the balance of intrusive versus extrusive magmatism are expected to be the hotspot swell volume flux Q s , plate hotspot relative speed v , and lithospheric elastic thickness T e , which can be combined as a dimensionless parameter R  = ( Q s / v ) 1/2 / T e , which represents the ratio of plume heat to the lithospheric heat capacity. Observational constraints show that, except for the Ninetyeast Ridge, R is a good predictor of topographic character: for R  < 1.5 hotspot tracks are topographically rough and dominated by volcanic edifices, whereas for R  > 3 they are smooth and dominated by intrusion.