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Tangaroa Blog #8 Getting to the core of it

20 months ago by Kate Boersen

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Today marks the second stage of voyage with a focus on core samples off various sites off the coasts of Hawke’s Bay all the way down to Kaikoura.

The geophysical scientists will now be assisting the geology scientists with their work and the entire team has been divided into three shifts.

The coring started at 5am this morning with a team of NZ and Japanese scientists led by Scott. The 4am to noon team managed to complete two multi cores sites off Hawke’s Bay.

Then this afternoon/evening at the third and fourth sites two more multi cores were taken by the Japanese and US team led by Jamie.

To get a ‘core sample’ the crew first put a transponder and larger multicore instrument over the side of the ship and depending on the water depth it takes around a hour-ish to float to the bottom of the seafloor.

The line holding the transponder then goes slack when the multicorer instrument reaches the sea floor and this then triggers the caps of the six plastic tubes to close and (hopefully) six full samples of sediment are taken measuring about 60cm long.

The multicore then returns to the surface, which again takes another hour or so (depending on water depth), to get winched back up to the surface by the ship’s crane and back on board.

The cores then get detached from the multicorer and hung on the make-shift multicore lab container for a fresh water wash down of the sediment of the outside of the cases.

The cores are then are visually analysed and sediment layers are noted down as well as sample length. From here one of the scientists decides which core samples will be used for different types of analysis that will be undertaken.

For the most part the core samples are sliced and diced and then bagged. Only one full sediment sample is taken.

At the end of the shift what you ended up with is around 60 snap lock bags of sediment from runny silt dark grey material to rusty red sediment, one full sediment sample and then two larger 5cm and 10cm pieces of sediment that get frozen.

The analysis of these then takes place back on land so in the meantime full steam ahead to the next site!