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Ocean Sediment Sampling: Methods, Purpose & Findings

Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this lesson, you'll see how ocean sediment sampling gives us a glimpse back in time. You'll also learn about the three methods used to sample the ocean's sediments.

Ocean Sediment Sampling Purpose

Joe is getting ready to board a research cruise. The ship's crew tell him they're going to take him far out to sea so they can grab some samples of the sediment in an area that hasn't been researched before. Collecting the stuff at the bottom of the ocean is called ocean sediment sampling.

Joe wonders, 'Besides dirt and sand, what possible information can they get by sampling the dirt that's on the ocean floor?'

Joe is about to find out. As they head out to sea and begin their work, Joe realizes that it's a 24-hour operation. There is always activity in the lab as different crews take over different shifts. Joe never thought it was such a big operation.

The crew tell Joe that sediment sampling has quite a few purposes. For one, ocean sediment sampling lets us learn about the mineral and chemical composition of the ocean's floors. The chemicals and minerals present in the ocean's floors can and do sometimes impact Earth's overall environment. Second, ocean sediment sampling also lets us learn about the life that lives on ocean floors. As scientists have continued their sampling, they have found that there is life, even at unimaginable depths.

Third, ocean sediment sampling is a way to learn about what happened to the Earth back in time. As time goes by, different layers of sediment emerge, so what is seen in lower layers gives a glimpse of what life was like 100 years ago, for example. This time travel through sediment sampling can go even further back in time.

Now, Joe is getting excited. That's quite a bit of information that can be learned from sampling the ocean's depths.

The particular boat that Joe is on is a fully equipped boat that can employ any of three different sampling methods. Let's see what they are.

Grabbing

The first is the grab method. This method, as its name implies, is performed by simply grabbing a sample from the surface of the sediment. Samples gathered this way allow researchers to study the mineral and chemical composition of the ocean's sediment, as well as any marine life that lives on the sediment surface.

Coring

The second method is that of coring. In this method, tubes are pushed down into the soft muddy sediment. These tubes are not small by any means. One tube can be as long as 10 meters. Machines called corers are used to push the tube down its length, then a marker is placed over the hole so that another tube can be inserted into the same hole to gather even more sediment. This process is repeated until the rocky bottom of the earth is reached.

There are different types of corers depending on what materials are brought up in the tubes. Sediment corers are used to gather a column of sediment material. Benthic corers are used to gather organisms found in the benthos, the bottom sediment.

Composite Sampling

The third method is composite sampling. In this method, samples from different locations are mixed together and then analyzed as a whole. Mixing samples from different locations gives a good idea of the overall composition of an area.

Uses & Findings

What kind of results or findings have been found by using these methods?

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