Abstract
Underwater volcanoes and their linear distribution on the flanks of mid-ocean ridges are common submarine topographic structures at intermediate- and fast-spreading systems, where sufficient melt supplies are often available. Such magma sources beneath the seafloor located within a few kilometers of the corresponding ridge-axis tend to concentrate toward the axis during the upwelling process and contribute to seafloor formation. As a result, seamounts on the flanks of the ridge axis are formed at a distance from the spreading axis and distributed asymmetrically about the axis. In this study, we examined three linearly aligned seamount chains on the flanks of the KR1 ridge, which is the easternmost and longest Australian-Antarctic Ridge (AAR) segment. The AAR is an intermediate-spreading rate system located between the Southeast Indian Ridge and Macquarie Triple Junction of the Australian-Antarctic-Pacific plates. By inspecting the high-resolution shipboard multi-beam bathymetric data newly acquired in the study area, we detected 20 individual seamounts. The volcanic lineament runs parallel to the spreading direction of the KR1 segment. The geomorphologic parameters of height, basal area, volume, and summit types of the identified seamounts were individually measured. We also investigated the spatial distribution of the seamounts along the KR1 segment, which exhibits large variations in axial morphology with depth along the ridge axis. Based on the geomorphology and spatial distribution, all the KR1 seamounts can be divided into two groups: the subset seamounts of volcanic chains distributed along the KR1 segment characterized by high elevation and large volume, and the small seamounts distributed mostly on the western KR1. The differences in the volumetric magnitude of volcanic eruptions on the seafloor and the distance from the given axis between these two groups indicate the presence of magma sources with different origins.
Highlights
Underwater volcanoes are the result of interaction between constructive and destructive forces during submarine volcanic eruptions [1]
Small seamounts near the spreading ridges are mostly associated with axial mantle upwelling under a steady-state process and lithospheric extension or cracking involving seafloor spreading [4,5,6], whereas seamount chains constructed by off-axis magmatism are more often related to anomalous melting in the asthenosphere and small-scale volcanic eruptions induced by fertile mantle heterogeneities [7,9,10,11,12]
The seamounts identified in the high-resolution multi-beam shipboard bathymetry data are distributed in three areas, on the flanks of the eastern, central, and western KR1, similar to the classification of the axial morphology of KR1 (Figure 1c)
Summary
Underwater volcanoes are the result of interaction between constructive and destructive forces during submarine volcanic eruptions [1]. Off-axis seamounts are active or extinct underwater volcanoes commonly observed on the flank of intermediate- and fast-spreading ridge systems, where sufficient magma sources are often available beneath the spreading seafloor to construct such topographic features [2,3,4,5]. Small seamounts (approximately
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