Core On Deck and Dropstones

Saturday, January 23rd, 2010

We got to our new site 2 days ago, and we are drilling!  Unlike the last site which kept destroying our drilling equipment, this site is going well.

In one day, we have drilled over 200 meters (over 600 feet).  Once you start drilling you have to go slow because otherwise you mess up the cores that we are trying to gather.

Going slow is ok though, because every core we recover has to be measured by many means.  The physical properties measurements Lambchop has been describing are just the first step.  Each core takes about an hour to do everything that Lambchop has been describing.  And that is just the first step!

After it goes through all the physical properties measurements, the core is cut into two pieces.  Each piece goes a different way.  We will follow these two halves later on.

For right now, Lambchop and I wanted to show you a picture of a piece of core we got today.

Most of this core is mud, which is made of very small pieces of rock, and the shells of very small plants called Diatoms.  Now diatom shells are really pretty, and very small.  Infact you can not see a diatom without a microscope.  Here is a picture of what one kind of diatom looks like.

In fact, this diatom is only 10 microns across, that is 0.0003 inches across, or if you put 3,300 of them end to end, it would only be one inch!

Now these diatoms are really important.  So important, that I will talk about them later!

But the pieces of rock Lambchop is pointing to are special.  These are called ‘dropstones’.  These pieces of rock used to be on land in Antarctica.  Then an ice sheet scraped them off, and carried them out to the coast.  Then a piece of the  ice sheet broke off, and became an iceberg.  This iceberg then floated out into the ocean, with these pieces of rock still in them!  Eventually the iceberg melted, and all the rocks that were in it dropped out here.  This is why we found them here! 

The amazing thing, is the iceberg that carried these dropstones melted over 10 million years ago.  That is way before cavemen and cavewomen were around.  So how do we know it happened then?  Remember the diatoms?  Scientists use their shells to figure how old the sediment is.  Now, the diatoms are really important, and I want to make sure I give you a really good explanation.  So we will have to come back to them later.

Now, Lampchop left her tour of the cores off after showing you the MS.  The next measurement taken is the PWL.

This sensor is called the PWL, or P-Wave Logger.  It measures the speed of sound in the core. 

Did you know that sound has different speeds in different things?  It is why your friends sound funny when they are in a swimming pool trying to talk to you.  This is a very important measurement for Lambchop to make.  This is because nobody has ever drilled in this area before.  The only clues Lambchop and the other scientists have to what is underneath the ocean is from something called Seismic Reflection surveying. 
This seismic reflection surveying is a lot like getting an Xray, only it is of the sediments underneath the water, rather then the bones in your arm or leg.  But this seismic reflection survey uses sound waves, instead of X-rays, and so knowing how fast the sound is traveling in the sediments is very important!

These three measurements are what the MST does.  It takes the Lambchop about 20 minutes to run each 1.5 meter piece of core (about 5 feet) through the MST.  The MST is actually measuring each of the measurements every 2.5 centimeters.  Do you know how many inches that is?

That’s right, the MST is making each measurement about once an inch!

So, stay tuned, because this is just a single step in the trip of the core around the lab.  Next Lambchop gets to take the core to the NGR!