31 January, 1998


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, Shackleton

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