Friday, 27 May 2011

Catch up to the Polygonal Faults

Since I last managed to post we have moved site. We took a 36hr trip (which actually took more like 50 hours as we tried to go around the storm) from the Darwin Mounds to the Hatton-Rockall Basin (between Hatton Bank in the West and Rockall Bank in the East). This involved diverting in the direction of Iceland to avoid the storm, resulting in a nice coating of ash on the ship due to our proximity to the erupting Grimsvotn volcano.

The long journey was spent mostly in rough seas with a session of amusing games one evening, mostly requiring physical tasks which were compromised by the pitch and roll of the boat- have you ever attempted a game of Twister in a force 10? I can tell you we had more than one balancing body turn into a bowling ball!

The rough weather is not very conducive to looking at computer screens and I too was finding I could not spend much time reading before my eyes started going funny.

We have been back in the calm weather now for a couple of days and I can tell you the rest is much appreciated from the constant adjustments and strains on your knees as you sway to stay upright.

The Polygonal Faults is a predominantly geologically interesting feature. Think of the Giants Causeway of hexagonal rocks on a scale of 1km per hexagon. The multibeam map looks like giraffe skin with these kilometre wide hexagons displaying acres of fine sand endlessly burrowed and turned over by unseen creatures. The gaps between hexagons are 30m deeper and the sub bottom profiler shows that there are deep fault lines fracturing the earth’s crust here. The geologists have not seen these so wide and are puzzling over the potential for fluid up-flow in the faults between polygons. There were some little “pimple” features on the multibeam maps that showed 3m deep, 10m wide depressions which were potentially indicative of gas escape points and the biologists were also interested in seeing if there might be any chemosynthetic communities living in such areas. However the ROV footage has shown a pretty uniform silty substrate, one of the pockmarks looked like it might have been a gas vent once, a depression filled with glacial boulders that may have accumulated in a pile when all the sand is continuously being blow outwards by bubbles of gas, but the only signs of life here was one large octopus! Other pimples turned out to be large boulders with giant scour pits behind them. One of these boulders did take everyone’s imagination, said to have looked like a shipwreck it was very pale, the size of a small house and had lines of tubular holes punctuating its surface, the origins of which everyone is still debating about. I’m afraid I was asleep at the time and therefore cannot weigh in until later when the photos and videos are available to view.

We are also undertaking piston cores, megacores, CTD readings and Niskin bottles for water sampling so that we can measure and assess the geochemical constitution of the sediment and the water column above and around the polygons, faults and pockmarks (testing for Methane, Oxygen and Hydrogen Sulphide content) which is what is still happening now until the weather turns for the worse again expected this evening.

Meanwhile, in spite of having a calm patch the phones and internet have been on the blink. The phones apparently are a fault with the service provider and they are blaming some other ship in the area who are overusing the frequency (somehow?!), hopefully they are working again now. The internet is a bit more mysterious, frequently taking funny turns and today the router burnt out with a fizzle, luckily being replaced by a spare they happened to have brought with them. Fingers crossed we stay connected now (at least in the good weather periods!).

Only a couple of pictures today, but I shall have polygonal fault examples for you tomorrow (internet permitting).

A game of home made twiser over the waves (from left: (back) Aggie, (front) Veerle, Colin, Steve and Ally). There were two bags containing bit of paper one containing left hand, left foot, right hand, right foot, and the other offering the colours. Easily done and hours of fun ;)

Our location at the polygonal faults, although since I typed the post above we have set off now for Rockall. More soon. :)

No comments:

Post a Comment