Dive FD-207 · Eastern Indian Ocean · 2025-11-04
Sunda Trench, north wall
First hadal-zone dive from this vessel. Sediment cores, and more plastic than anybody wanted to report.
- Max depth
- 6,740 m
- Bottom temp
- 1.6 °C
- Vessel
- RV Sounding
- Lead
- Dr Anjali Varma
Notes
At 6,740 metres the pressure is about six hundred and seventy atmospheres. Everything on the vehicle that contains air has to be either very strong or not there, which is why the lighting rig for this dive was oil-filled rather than sealed.
The intended work was three sediment cores from the trench wall, to look at how organic matter accumulates on a slope steep enough that most of it should not stay. All three cores came back intact.
The unintended finding is in the cores as well. Every one of the three contained plastic fragments, the deepest at 41 centimetres of sediment depth, which on this slope is a rough century. We are not the first to find this and we would rather not have confirmed it.
Logged on the bottom
- —Sediment cores, 3, all intact
- —Plastic fragments in all 3 cores
- —Amphipods at the bait lander, 200+ individuals
- —Snailfish, 2 observed at 6,600 m
Descent
Sunlight, 0 to 200 m, is the band at the top too thin to letter.
Water column, descent cast
| Depth | Temp | O₂ | Note |
|---|---|---|---|
| 0 m | 29.1 | 6.4 | Surface |
| 500 m | 9.8 | 2.2 | Thermocline passed |
| 2,000 m | 3.2 | 3.0 | Deep water |
| 4,500 m | 1.9 | 3.6 | Abyssal plain depth |
| 6,740 m | 1.6 | 3.7 | Trench wall, core site |
Oxygen in millilitres per litre. Casts are raw, uncorrected for sensor drift.