Survey Time

Cleverson and Gary discussing possible coring sites.

Today has been mostly slow and relaxing around the lab. Gary and I (and now Andy) have been logging yesterday's long core, some of us managed to get an hour or so of sun time out on the deck before the clouds rolled in, and the most of the students have been reading and playing cards. But, after almost 24 hours of this, we'll soon (by about 10 pm local time) starting work on our next sampling site.

Why such a lazy day on a high-powered research cruise?

It is all about the surveying.

One of the goals of the cruise is to get a good high-resolution survey of this area. These kind of data do not exist and are essential to any detailed study. The data are important for future work, but they are also important for the work we are doing on this cruise.


So, although to many it may have seemed like a slow day, in reality we have been collecting data constantly.

A few days ago, someone asked why our cruise track looked like a square. This map of the cruise track so far, makes it pretty clear which part of the cruise she was referring to!

Believe it or not, this path our been completely intentional. No, it was not completely pre-planned, but a lot of it was (thank you Cleverson!) and the parts that were not planned before the cruise were chosen based on what we saw in the preceding days and hours.

While conducting these surveys, the on-board equipment collects bathymetric (depth) data, information about the bottom roughness and variation in bottom substrate, and information about the subsurface sediments and stratigraphy. The main instruments we rely on for this information are the Sea Beam and Chirp systems.

The Sea Beam system is a multibeam echo sounder that produces high resolution bathymetric contour charts of swaths the seafloor, like the one seen here from one of our first surveys. The swaths of map track the path of the ship.

The Sea Beam system also produces gray-scale swath maps (side scan sonar maps) of the seafloor terrain that can help us determine the bottom roughness and the nature of the bottom sediments.

Finally, the Chirp system is a single-channel, high frequency seismic system. It collects information about the sub-bottom sedimentary sequence. The output is in the form of a cross section of the sediments below the seafloor, showing bottom topography and the large-scale internal structure of the strata.

A main purpose of this cruise is to collect a detailed record of the history of climate change. We are likely to find the best climate record in sediments that were deposited quickly and conformably -- as opposed to in sediments that have been disturbed by faulting, by submarine slumping, or by some other post depositional movement. Such movement can erode significant portions of the previously deposited sediment -- erasing any climate record that they may have contained.

So, when we're looking for places to core, we avoid the submarine canyons (such as the Amazon Canyon and its tributaries) and we look for nicely conformable and undisturbed sequences of strata. We avoid places like look like the image on the right (below). Instead, we look for places that are similar to the one on the left -- we look for places with nice, undisturbed strata that are likely to have good, continuous climate records.

And as luck (and pre-planning and skill) would have it, we've found another such place. Soon the lab will be buzzing as we prepare for the next round of sampling. I believe another full Monty is on the POD. We're ready!