2000/04/10 by Daniel S. Scheirer, Donald W. Forsyth, J. A. Conder +4 · 41 citations
Earth and Planetary Sciences · #earthquake and tectonic studies #Geological and Geochemical Analysis #High-pressure geophysics and materials #Geology #Hotspot (geology) #Seafloor spreading #Lithosphere #Crust #Plate tectonics #Volcanism #Seismology #Mantle (geology) #Tectonics #Transform fault #Paleontology #Geophysics
paper · doi:10.1029/1999jb900407
published in Journal of Geophysical Research Atmospheres 105(B4), 8243-8262 (American Geophysical Union)
openalex publication_date 2000/04/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23
The Amsterdam‐St. Paul Plateau is bisected by the intermediate‐rate spreading Southeast Indian Ridge, and numerous geophysical and tectonic anomalies arise from the interactions of the Amsterdam‐St. Paul hotspot and the spreading center. The plate boundary geometry on the hotspot platform evolves rapidly (on timescales <1 Myr), off‐axis volcanism is abundant, the seafloor does not deepen away from the axis, and transform faults do not have fracture zone extensions. Away from the hotspot platform the ridge‐transform geometry is typical of mid‐ocean ridges globally. In contrast, the Amsterdam‐St. Paul Plateau spreading segments are shorter, they often overlap each other significantly, and the intervening discontinuities are smaller, more ephemeral, and more migratory. Abyssal hills are smaller and less uniform on the hotspot platform than on neighboring spreading segments. From gravity and isostasy analysis the average thickness of the platform crust is ∼10 km, approximately 50% thicker than that of typical oceanic crust. Most of the isostatic compensation of the hotspot plateau occurs at the Moho or within the lower crust, and the effective elastic thickness of the plateau lithosphere is ∼1.6 km, less than half that of adjacent spreading segments. Away from the platform some transform faults contain intratransform spreading centers; on the platform the two transform faults have valleys which may be depocenters for abundant axial or off‐axis volcanism and mass wasting. Although not wellconstrained by magnetics coverage, the Amsterdam‐St. Paul hotspot appears to have been “captured” by the Southeast Indian Ridge, enhancing crustal production at the ridge since about 3.5 Ma. Prior to this time the hotspot formed a line of smaller, isolated volcanoes on older Australian plate. The underlying cause for the present‐day crustal accretion anomalies is the effect of melt generation from separate sources of mantle upwelling (due to plate spreading and the hotspot) which has a consequent effect of weakening the lithosphere.