Seafloor evidence for pre-shield volcanism above the Tristan da Cunha mantle plume

Wolfram H Geissler,Paul Wintersteller,Marcia Maia,Tonke Strack,Janina Kammann,Graeme Eagles,Marion Jegen,Antje Schloemer,Wilfried Jokat

doi:10.1038/s41467-020-18361-4

Abstract

Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times.

Highlights

Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot
Nearcomplete coverage was achieved at the intersection of the transform fault and fracture zone (TTFZ) with the Mid-Atlantic Ridge (MAR)
The Geographic Information System (GIS) based Benthic Terrain Modeler (BTM) and backscatter analysis were used for mapping volcanically altered oceanic terrain based on objective criteria

Summary

Introduction

Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. 1234567890():,; Many intraplate volcanic ocean islands are seen as manifestations of hotspots that indicate the presence of underlying mantle plumes. These islands can be the emergent parts of well-developed shield, postshield, or rejuvenated volcanic edifices[1]. We report here the discovery of relatively young volcanic cones and lava fields west of Tristan da Cunha (TdC) in the less-studied South Atlantic. TdC is an intraplate volcanic island in the southern Atlantic Ocean, located at 37°06′S and 12°17′W (Fig. 1), about 450 km east of the Mid-Atlantic Ridge (MAR) and 60 km north of the TdC transform fault and fracture zone (TTFZ) system. In 2004, earthquake activity and pumice stranding on the island’s eastern beaches were attributed to a submarine eruption south of the main island[8,9,10]

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