A few times a week, at night, a DOG is thrown overboard.
I am altering the facts a bit here. The DOG is really not thrown
overboard, it is carefully lifted over the side with a crane and allowed
to sink to the bottom. After a few days, the DOG is ordered to come back
to the surface and is retrieved by the crane for a little rest. This is
also a very special DOG.
There are research cruises that go to different areas of the world and
drill holes in the ocean floor. The samples that result are long tubes
with the newest rock on the top and the oldest rocks on the bottom. The
cores are only a few inches in diameter and vary from site to site in the
ocean. Cores can also be limited by the type of rock that is being drilled
since it is easier to drill through soft sediment than through hard
basalts. To get around some of these problems, scientists have developed
other techniques to examine the Earth beneath the immediately visible
surface. Enter a DOG.
A DOG, or Deep Ocean Gravimeter, is used to measure how much the ocean
bottom moves on a daily basis. By looking at how much the ocean floor
moves on a daily basis, Wayne Crawford from Scripps Institution of
Oceanography is able to answer questions about how the crust is formed at
a mid-ocean ridge.
After the DOG has been released from the ship, Wayne sends a signal from
the ship to the DOG. The DOG will send a signal back to the ship to let
Wayne know whether or not it is ready to begin measurements. At the end of
the experiment, Wayne sends a signal to the DOG telling it to come back to
the surface where it will be picked up out of the water by the crane.
Back on deck, the data are retrieved and the DOG is sent down for another
day of lying around.
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