Earth and Planetary Science
EPS Near-Surface Geochemistry and Geobiology

Berkeley Geophysicists Observe and Analyze Rough versus Smooth Topography

Friday, March 3, 2017

Felipe Orellana-Rovirosa and Mark Richards are authors of “Rough vs. Smooth Topography along Oceanic Hotspot Tracks: Observations and Scaling Analysis.” The article came out in Volume 44, Issue 3 16 February 2017 of the journal Geophysical Research Letters.

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, Hawaii-Emperor). Smooth topography occurs when the lithospheric age at emplacement (LAE) 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 vs. extrusive magmatism are expected to be the hotspot swell volume-flux Qs, plate-hotspot relative speed v, and lithospheric elastic thickness Te , which can be combined as a dimensionless parameter R = (Qs / v)1/2 / Te , 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.

Felipe Orellana-Rovirosa is a doctoral candidate in the Berkeley Earth & Planetary Science Department (EPS). Marks Richards has been a professor in the EPS Department since 1989. He received his undergraduate degree from the University of Texas at Austin and his PhD in geophysics from Caltech.

For the full-length article please click here.