Multibeam bathymetry from this cruise revealed a NW-SE trending “pear-shaped” planform with a size of 44 km × 37 km and a narrow northwest end and a broadened southeast termination. The seamount exhibits a relief of 2475 m, with a minimum water depth of 1775 m at the summit and 4250 m at the base, characterized by a flat top and steep slopes. Based on trawl samples and seafloor imagery, calcium-rich sedimentary rocks (reef limestone, carbonates), with occasional basalt outcrops, comprise the upper slopes, while the lower slopes predominantly consist of a basaltic basement with localized low-calcium sediments (mudstone). On the basaltic bedrock, hydrogenetic polymetallic crusts are commonly developed.
The basalt samples from the Ewing Seamount exhibit a thin, layered crust (2 cm thick) on the surface, although most of the crustal material was spalled off. Distinct weathering zones are distinguishable on the basalt: a strongly weathered and altered layer (1–2 cm thick), with a brownish-red color at the top, underlain by a weakly altered layer (2–3 cm thick) of grayish-brown hue. The interior consists of relatively fresh dark gray-colored basalt. Petrographically, the rock exhibits a porphyritic texture and a massive structure, with well-developed vesicular and amygdaloidal structures. Vesicles are predominantly sub-rounded to irregular in shape, ranging from 1 to 3 mm in diameter (~10% abundance), with no preferred orientation. In the surface basalt, vesicles are partially filled with white minerals (phillipsite, calcite), while those in the fresh interior basalt remain largely unfilled.

Other Regions, Features and Areas containing this locality

References