Early on Friday morning (around 2 AM), our science team got our first
gravity core! This gadget is one of the most reliable tools for
collecting marine sediment from the bottom of the ocean. It is kind of
shaped like a long pipe, with a bunch of lead weight at the top, and
an empty 8-foot-long plastic tube in the middle of the pipe. The whole
thing weighs about 800 lbs., and when deployed correctly, the pipe
goes into the seafloor straight up and down, with the lead weight
providing enough mass to push the gravity core deep into the sediment.
After the ship uses its powerful winch to pull the gravity corer back
to the surface of the ocean, and we haul it back onboard, we remove
the plastic tube – which is now filled with a great sample of sediment
from over 6000 feet underwater!
I bet you are wondering what sediment is – this is all the solid stuff
that slowly settles out of ocean water to the seafloor, and includes
all sorts of things, like mud from rivers, dust from deserts, the tiny
bodies of plankton, sometimes even volcanic ash or rocks from
icebergs! Most of these things are too tiny to be seen by the naked
eye, so marine geologists use microscopes to magnify the sediment for
Now, I bet you are wondering why anyone would want to collect marine
sediment. There are lots of reasons, but at least for my research
(Jason), I use chemistry to reconstruct past ocean conditions. The
sediment at the bottom of the gravity core may be over 1,000 years
old, while the sediment at the top is much younger, perhaps as old as
only 1 or 2 years. When we get back to land, I’ll take these cores
back to my lab at the US Geological Survey and study them for many
years to come. Who knows what exciting stories the ancient ocean has
Jason with the gravity corer.
It takes a lot of hands to deploy the corer.
Bringing the corer back on deck. If you look closely, you can see mud at the bottom, where the instrument pushed into the sediments.
Amy and Ryan (on the left) adjust the schedule while Joe and Jason (Jason on the right) show off their core.