Mud on the deck – and in my mouth

End of the ship, Finnish flag.

Early in the morning we leave from the Marjaniemi harbour, in Hailuoto, towards west, to Swedish border. We are at the southern edge of the SEAmBOTH project area. Today we were aiming to recover short sediment cores from the deep waters. Why bother, someone could ask? – To understand how the sediment is moving and what kind of material there is in the dark bottoms of these northern Baltic Sea waters.

This morning sea is calm and so beautiful. RV Geomari is speeding up towards west, with her maximum speed, 20 knots.

Time flies, and suddenly we are approaching the first sampling site. We selected this site according to acoustic-seismic profiles that were surveyed last year. Echo sounder profiles indicated a nice sediment drifts, contourites, in this area. We approach the site slowly using an echo sounder just to check that seabed at the site looks OK. After confirmed that, we stop at the site, and let a dynamic position (DP) system to keep Geomari still.

Mud pants, safety wellies, helmets and life vests on, and we are ready to rock, meaning to mud (?).

Work at the site, or at the station as we sometimes call it, starts with recording underwater video from the seafloor. Drop camera goes down in to the deeps…………and since the video also confirmed that the seabed is suitable for sediment coring, we started coring with our GEMAX corer.

Mud on the deck. It is always exciting, still after all of these years, to receive the first sediment cores on the deck. This core is the first sediment core this summer.

Sample tube full of mud.
Short sediment core on the deck.

After describing the core through plastic core liner, core will be splitted for closer inspection. We geologists are a pit strange species, as we love to look, sniff, touch and even taste the sediment.

2 persons holding a sample tube on the deck.
Preparation for the core splitting.

A splitted sediment core provide useful information on sedimentary environment and changes in it. Sometimes these changes are visible in the sediment.

35 cm long sample.
A splitted short sediment core.

After photographing and describing of the splitted sediment core, the other core(s) from this site were sliced into e.g. 1 cm slices. And those sediment slices were bagged into sample bags, and put in the fridge to wait transport to shore and laboratories.

Pile of sample bags, a person writing on one.
Bagging the mud.

From the sediment analysis, we will receive a lot of information, like; on the age of the sediment, on sedimentation and erosion processes, and on geochemistry of the sediment including anthropogenic loading.

Scientists around the world are currently defining timing of the new geological era, Antropocene, the era when we humans have left a distinctive set of marks preserved in rocks, seafloor mud or glacial ice, which indicates a fundamental change in our planet. Is it the beginning of the atom bomb test for example? Those signs can be seen probably also in these Bothnian Bay sediment. Similarly, the traces of the unlucky Chernobyl nuclear power plant accident in April 1986 can still be seen in these sediments as increased e.g. cesium 137 concentrations.

Maybe it is not so healthy to taste those younger sediments and test the sediment grain size between teeth’s, as we geologist normally do. But it is difficult as we just love mud. By the way, mud reminds me mudcake that was baked today, as quite often when we have these mud sampling campaigns. So maybe a piece of sweet and soft mudcake and a cup of coffee, but just after washing mud away from the deck. And then towards the next site. Sea is still so calm. Hopefully it stays like this.

After several successful stations we headed to Marjaniemi harbour for the night. To make dinner, and have a sauna, hopefully. This day was good. It is not always that way. But these good days and peaceful evenings give us strength to continue, and to wait even better tomorrow.

A ship.
Geomari in Marjaniemi harbour.

Aarno Kotilainen, GTK


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