31 January, 1998
Hello! Here are our coordinates for today: 74 degrees 00 minutes latitude south 175 degrees 00 minutes longitude east Wow! Where were we when I last wrote? If you have been plotting our positions, you probably have seen that we sometimes stay in one area for a long time and then jump to another area. Why do you think our position stays the same and then jumps so much? If we seem to be moving slowly, it probably means that we are collecting data - our images of the sea floor and water information and sediment samples. When our position changes quickly, it probably means that we are moving from one study or survey place to another - or transiting. Well, since yesterday we moved from Pennel Coast back to Ross Sea. We finished our survey along Pennel Coast and are starting our work in the new area. The last information we collected from Pennel Coast was from the shallow banks between the deep troughs that I wrote about last week. These banks are like flat table tops on the sea floor. We surveyed the bank tops with our imaging equipment. We saw huge grooves that looked like giant earthworms had traveled across the banks. What might have carved these grooves? Hint: We see big icebergs floating in the shallow water above the banks tops. Sometimes these icebergs seem to get stuck! We took grab samples of the bank tops and found black volcanic sand and some corals and some bryozoans. Corals?! Yes! Some corals can grow in very cold water - they need clear water and enough food. The bryozoans are also colonies of tiny animals. Bryozoans build a structure that looks like coral fingers. Sometimes they look like tiny fans. We did not find much mud. The sand was very "clean" - the water that we ran through it came out clear, not muddy. What happened to the mud? If you go to the beach is the water muddy? In most places the beaches are made of sand and there is very little mud. Why do you think this is? We used an instrument called a CTD - it measures the salinity, temperature, and depth of the ocean. A CTD can also collect water samples from the deep ocean water. Scientists use a CTD to study the different water masses in the ocean. Our ocean has many different water masses - each has its own temperature and salinity. The colder the water mass is, and the saltier the water mass is, the "heavier" it is - it will sink below warmer and less salty water masses. The CTD helps us learn where the different water masses are. Our CTD measurements showed us that a different water mass was moving across the banks. This water mass had stronger currents - something like currents in a river or at the beach. These currents carried the mud away, but were not strong enough to carry away the sand. This is why the grab samples we collected were so sandy and not muddy! We spent the transit time wrapping up the study along Pennel Coast. We carefully labelled the data. We made sure our cores were numbered and recorded correctly in our log books, and that all the information we collected from the sea floor was properly listed in the log, too. Why do you think we want to do this? I hope you are doing well! Yours truly, ShackletonReturn to E. Shackleton Bear's Page
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