21 January, 1998
Hello Everyone! We are on our way to Cape Adare. It is at the northwestern corner of the Ross Sea (the bottom right-hand corner of Antarctica on most maps). It is very beautiful. The Transantarctic Mountains line the western edge of Ross Sea, so that part of the coast has beautiful mountains and glaciers coming right to the ocean. There is a lot of sea ice here, and it is a little noisy moving through it with the ship. The sea ice is in big plates, about 15 feet wide and two feet thick. The plates are floating on the ocean surface. The penguins and seals like to sit on these plates in the sun. I have seen many Adelie Penguins today. There have been some sightings of Orcas, but I have not been able to get on deck fast enough to see one! We are using many types of equipment to find out what is on and under the sea floor, but there are two main types. One type uses sound to "make pictures" of the sea floor and the other type actually gets samples of the sea floor. The first way we get pictures of the sea floor and what is under it is by using instruments to send a sound wave into the water. Some of the instruments are towed behind the boat and some are attached to the boat. The instruments send out a sound, like a beep or a boom, every few seconds. The wave travels to the sea floor. Some of the sound bounces off the sea floor and some of the sound goes into the sea floor and bounces off layers in the sea floor. The sound waves bounce back to the surface. The deeper the sea floor (or the layers under the sea floor) the longer it takes for the sound to travel to the layer and back to the surface. At the surface there are listening devices - kind of like electronic ears. These "ears" "hear" the sound as it comes back to the surface and they send it to the computers and printers on the ship. The sound is translated into an image. You may have been on a boat and seen instruments that follow the bottom, sometimes these are called "fish finders" or "bottom profilers" - they use sound to trace the bottom under the boat. You can try making your own sound wave by using a slinky. Sit on the floor with a friend about two feet apart. Have your friend hold one end of the slinky and you hold the other. Have your friend make a wave in the slinky by pushing it or shaking it. Did it travel fast? Now move about six feet away from your friend and make another wave. Did this take longer to reach you? This is just like sound - the closer the sea floor is, the faster the sound moves from the source to the ears. The farther the sea floor is, the longer it takes for the sound to move from the source to the ears! The pictures we get show the layers of sediment and rock below the sea floor. This is a little like looking at the side of a cake that has been cut in half, only, instead of icing and cake, there is rock and mud. We can sample the layers and trace the layers over the ocean floor. Some of the layers were made by the glaciers. These are the layers we want to find! There is another type of picture of the sea floor we get and that is a picture of the surface. it looks a little like a photograph or a map. We get this picture in the same way, using sound, but the sound waves are so high frequency, they do not go into the sea floor - all of them bounce off and back to the listening devices. This instrument (called a side-scan sonar) lets us see features on the sea floor, like grooves carved into the sea floor by giant icebergs! Tomorrow I will tell you all about how we get samples from the sea floor! This is very messy - but it is the part I like the best! Write me soon - I hope you are fine! E. Shackleton BearReturn to E. Shackleton Bear's Page
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