The dirt of the ocean…

Yesterday we spent most of the day collecting cores from the seabed.  So, what is a core…well, if you can imagine sticking a tube into the ground and pulling it out with a plug of the bottom.  Think about it this way…know when you have a drink at a restaurant, waitress gives you a straw…the you put the straw in your drink and put your finger over the top and pull some drink out of the glass in your straw.  You have essentially created a suction in the straw allowing the drink to remain in the straw when you remove it from the glass.  We are doing essentially the same thing, but on the sea floor.  This allows us to collect "sediment" from the ocean.

 

To be clear, sediment is the dirt, the soil of the ocean.  Particles that wash of the continent or are created in the water column sink through the depths of the ocean and accumulate on the sea floor.  This has been happening for thousands, hundreds of thousands of years.  So, these sediments hold a record of earth's history…information on ocean properties, changes in climate, alteration of the coast.  All of these processes influence the physical and chemical character of the sediments being deposited on the sea floor.  So, we collect these sediments to gain information on processes that are occurring in the overlying water column, the atmosphere, and the adjacent continents.  These sediments act as a window into the geologic and recent past.  The longer core we collect (longer straw), the further back in time we can see…

 

Given that background, we are interested in using these cores to gain a better understanding of how the continental margin, particularly the shelf-slope break, off NC, has changed and processes that lead to the accumulation or down-slope transport of sediments.  We use geochemical tools (natural radionuclides, organic matter, among others) and physical character (grain size, porosity, bulk density, etc.) of the sediments to interpret the source, mechanisms of delivery, age, and how the sediments have been altered with time.  The data collected form the sediments, together with the information gained from the multibeam, EK80, and Knudsen (se earlier blog post) will provide the initial data for several working hypotheses we hope to test in greater detail in the near future.