Johnston Atoll, Pacific Ocean - Images

Figure 1.

Perspective view of cow pies and oceanic basement structures covered by a thin blanket of sediment. “Cow pie” is an informal term used to describe flat-topped volcanic hills that are commonly seen on the abyssal Pacific Ocean seafloor. Some cow pies have a central caldera on the summit, some do not. The cow pie in the center-left of the image has a basal diameter of 4.7 km and the summit stands 350 m above the 5300 m deep abyssal seafloor. The summit caldera has a diameter of 970 m and is ~70 m deep.

The basement ridges reflect the relief of the oceanic basement inherited by the seafloor-spreading process. The basement is blanketed by only a thin sediment cover even though the basement age is older than 83 Ma.

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Figure 2.

Perspective view of the bathymetric gap between Karin (Sculpin) Ridge and Horizon Guyot. White dashed lines outline a  300-m high platform that spans the gap between Karin Ridge and a spur of Horizon Guyot. Cross section A-A’  trends transverse across the platform. Abyssal depths are deeper than 5200 m.

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Figure 3.

Perspective view of the bathymetric gap along the trend of Keli Ridge. The white dashed line outlines a 450-m high platform that spans the gap in Keli Ridge. Cross section A-A’ trends N-S through the gap at the lowest point.

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