5 February, 1998

Good Afternoon!

Our present position aboard the Research Vessel Nathaniel B. Palmer:
75 degrees 44 minutes south latitude
174 degrees 49 minutes east longitude

Today I helped to describe cores we have collected!  We have taken 
several cores and grab samples in Ross Sea.  We are seeing a pattern to 
the features and types of sediment that we see.  

The cores that are the farthest out to sea have the thickest green mud on 
them.  These cores have sediment that contains tiny fossils of marine 
animals.  The sea floor has big grooves and medium sized grooves and 
small grooves  that go in every direction!  Closer to the Ross Ice Shelf 
our cores collected hard sediment that has a thinner green mud on top.  
There are lines on the sea floor. Between these two places there is a big 
pile of sediment.  How would you explain all these observations

The research team works together to build stories or "models" that 
explain all of their observations.  If a parcticular story does not 
explain all the observations, they continue to change the story until it 
accounts for everything.  If an observation shows that a story is not 
correct, then they try to create another  story that will explain the 
observation.  If they have different stories that may be correct, what do 
you think they do?  They try to make an experiment that will help them 
test which story is correct.

The story that the research team is testing right now is that the 
glaciers grew across the Ross Sea.  As they grew, they scraped the 
underlying rock, making lines on the sea floor (called striations).  The 
glaciers were very large and very thick.  They compressed the sediment 
under them and made it very hard.   The glaciers acted like a bull-dozer 
and pushed and carried lots of ground-up rock with them. The glaciers 
stopped where the big pile of sediment occurs.  The pile of sediment is 
called a moraine.  In front of the glacier, the environment was the open 
ocean, so diatoms lived there.  The diatoms make the sediment green.  The 
grooves that go every which way are made by icebergs.  You can see 
icebergs today. Sometimes these icebergs tip over and cut into the sea 
floor.  This makes grooves. The glacier goes only in one direction.  The 
icebergs can move freely in the open ocean. They drift with wind and 
ocean currents.

But.....could the glaciers have gone farther than the moraine?  Might the 
moraine been put in place as the ice sheet pulled back?  To test this 
model, our research team is looking for evidence that the glaciers did or 
did not go past the moraine in the last ice age.  What might we look for? 
 How about other moraines or hard sediment in front of the moraine?  We 
are looking carefully for this information so that we can determine which 
story best fits our observations!

Yours Truly,

E. Shackleton Bear