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 Bear