22 January, 1998
Hello Everybody! We collected cores and grab samples from the sea floor. I told you all about how we image the sea floor using sound. That is called "remote sensing" - it means that we do not touch what is on the sea floor, instead we get a "picture" of it. But we also want to get a sample so that we know what our picture represents. We see layers under the sea floor and we want to know what makes those layers. We use a "grab sampler" to get a sample from the surface of the sea floor. This looks like a big steel mouth that is lowered to the sea floor on a long cable. When it reaches the sea floor, the mouth shuts, "grabbing" a sample of the material on the sea floor. The grab sampler is then brought up to the surface and we can see what is on the sea floor. We got mud and dark sand in one sample, with barnacles and brittle stars (like starfish with long thin arms) and tiny animals called bryozoans. You can find out more about these animals in an encyclopedia or by using the Internet. Why do you think the sand was dark? I'll give you a hint - what color are the sandy beaches of Hawaii? What has created the islands of Hawaii? The sample was "grabbed" near Cape Adare - what might this tell us about the rocks of Cape Adare? A corer is a long hollow pipe that is about 3 meters long and made of steel. How long is that in feet? Is the corer taller than you are? It has a big weight on top that weighs about 2000 pounds (much more than me!). The corer is attached to a cable on the ship. The corer is lowered to the sea floor. It slides into the sea floor, sampling the layers UNDER the sea floor (the grab sampler gets the layer at the top of the sea floor). The corer is then brought back up to the ship. What is inside is a sample of the layers. We lower the corers and grab samplers to the sea floor at 50 meters a minute and bring them back to the ship at the same speed. If the sea floor is 200 meters deep, how long does it take us to get a sample from the sea floor and back to the ship? Remember that we have to send the sampler down AND bring it back up! We use the grab sampler to tell us what type of sediment is at the sea floor. Sometimes there are big rocks at the sea floor. When this happens, we cannot collect a core because we might damage the equipment; the grab sampler gives us a good idea of whether or not we should take a core. You can take your own core! Have a friend make a peanut butter and jelly and marshmallow and banana sandwich for you, and you make a sandwich for your friend. I really like the marshmallow! You don't have to use all the materials, and if you want a different sandwich, make that one! Keep the layers of the sandwich secret from each other. Put each sandwich in a container (maybe an open lunch bag) so that you can see the top of the sandwich but not the edges. What do you think is in the sandwich? What is the order of layers? When we core the sea floor, we do not know the layers. If we have a grab sample, we may know what is on the very top. Take a clear plastic straw and poke it into the sandwich. Carefully pull the straw out. Do you see layers? What do the layers tell you? Which layer came first? Which one was put on last? If you take several cores, can you see a difference in some of the thicknesses of the layers? What does that tell you about the layer in the sandwich? Now comes the fun part - you can EAT your cores! I can't eat the ones we collect - mud doesn't taste as good as marshmallow! Why do we want to take cores in Ross Sea? What do they tell us? I'll write all about that tomorrow! More soon! E. Shackleton BearReturn to E. Shackleton Bear's Page
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