The above dive track schematic (not drawn to scale!) and video frame grabs A-F summarize the different geomorphologies encountered during EX1806 Dive 04, from a flat sediment plain (A), through the increasing slope of the stair-step terrace (B and C), to the nearly vertical scarp (D and E), and the scarp’s flat-lying rocky top (F).
In summary, the EX1806 – Dive 04 intra-slope terrace seabed is characterized as having areas of both higher abundances and diversity of benthic organisms where the slopes are steep, owing to the exposure of hard substrate on which invertebrate organisms can attach. Dense, diverse communities of sponges and coral are also home to echinoderms, arthropods, fish and many other mobile organisms. Flatter areas of the terrace’s stair-step slope are mostly buried in a sediment blanket and are not conducive as habitat for these biota, except where rock slabs have been swept clean by currents. The top of the terrace is home to large corals and some sponges, though distributed in low densities, likely due to the sediment cover.