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> 8-23-05: Interesting Mud! - by Ruben Fritzon
Ute_Kaden
post Aug 23 2005, 11:22 PM
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Interesting Mud!
8-23-05 - Posting by Ruben Fritzon (Swedish Teacher)


Longitude: 157 12.349 W Latitude: 76 25.964 N
Depth: 1173 m Speed: 3.9
Heading: 9.5 Water Temp: -1.369°C
Salinity: 2.7%

The boat is now full of activity with many projects going on at the same time. The last few days I’ve been working with the coring team together with most of the Swedish people. By pushing a pipe into the bottom of the ocean, and collecting the sediment that’s get into the pipe, we get 7 to 15 meters of sediment. The amount of sediment falling down to the bottom from the water above varies in between 1 to 10 cm every 1000 years. This means; If we get a core with 10 meters of sediment we collect sediment from millions of years. Because of the variation of the environment and the biological activity in the ocean, different kinds of materials fall to the bottom. This makes it possible to see different layers in the cores. By looking at the layers and analyse them the scientists try to get a picture of how the climate has varied in time.

IPB Image
Different sediment layers. Note the stone

After the cores have been taken aboard we cut them in sections of 1.5 meter. The scientists analyse them with an advanced analyse equipment. To make it possible to study and describe the different layer in the cores we need to split them in halves to see what is inside. John and I did this for several days.

IPB Image
John and Ruben splitting sediment cores.

In one of the cores we found a pretty big stone.
IPB Image
Stone found within a sediment core. Same stone pictured in first photo.

Finding a stone on the bottom of the ocean may not sound very dramatic. But the fact that the rest of the 15 meters of core is all clay and mud makes the stone very interesting. How did the stone end up in the middle of the ocean? Presumably the stone froze into a glacier thousands of years ago. When the glacier calved an iceberg into the ocean the stone was transported away from the shore. After a while the iceberg melted and the stone was dropped to the bottom. These stones are actually called dropstones. The presence of dropstones tells us that land around the Arctic Ocean was covered with ice, at least for a period. By studying the droppstones and other material transported by the ice the scientists can find out were the ice came from. Did you know that the Arctic Ocean was not always covered with ice? Cores obtained from deep sea drilling last year showed that the surface water of the Arctic Ocean used to be much warmer, about 20°C 50 million years ago.
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