NPB-9507 Weekly Cruise Report #1 ...
RVIB Nathaniel B. Palmer
28 October - 2 November 1995
Punta Arenas, Chile
The scientific party members from the University of Texas at Austin
left Austin on the 23rd of October. We rendevoused with Richard Von
Herzen of the Woods Hole Oceanographic Institution, Scott Borg of the
National Science Foundation, Amelia Shevenell of Hamilton College, and
Steve Stevenoski of Wisconsin Rapids High School in Miami. We were met
in Santiago by the Agunsa agency personel and stayed in the Hotel Monte
Carlo in Santiago. While in Santiago, Scott Borg and I visited Sergio
Barrientos and Emilio Vera of the Geophysics Department of the
University of Chile. On the 25th of October we met Dr. Marta Ghidella
of the Argentine Antarctic Program and Rick Pearce of Innovative
Transducers Inc. (Ft. Worth, TX) at the Santiago Airport and flew to
Punta Arenas. Most of the scientific party stayed at the Hotel Jose
Noreiga in Punta Arenas. We settled in aboard the ship on the 26th but
found that the ship had not been fueled while at the pier and that one
ASA employee would not arrive until the 27th. Consequently, rather than
sailing on the 27th as scheduled we did not depart the fuel pier until
the morning of the 28th.
Drake Passage
We left the Straits of Magellan and sailed around the eastern tip of
Tierra del Fuego. At 0805 on the 29 October 1995, we dropped a pressure
gauge for Wentworth of Texas A&M. It, in conjunction with another
instrument to be dropped near Elephant Island and some British
instruments, will be used to determine flow rate and volume of water
through Drake Passage. Total time on station was about 1.5 hours. We
then proceeded along the continental margin on the southern side of
Tierra del Fuego. We ran along at water depths varying between 1000 m
and 3000 m. This was the first real trial of the new, improved Seabeam
2112. I am happy to say the system works well. We continued on course
across the Shackleton Fracture Zone Ridge that extends from South
America to the Antarctic Peninsula. We crossed the flat trench at a
depth of ~4300 m and then turned northwest for a short survey, ran up
the continental margin of South America, and found the southern corner
of South America where the contours come to an angle of 50 degrees. We
then headed down the start of the Shackleton Ridge using the Geosat
gravity maps of David Sandwell. The ridge has one major offset at about
66-degrees 30-minutes W which we aniticipated from the Geosat gravity
data. We then were able to follow the ridge without any problems all
the way across the Drake. In the northern part of the ridge, it does
not match the published position very well but with the new Seabeam
system, it was quite easy to follow across. We did one additional quick
survey of the intersection of the abandoned spreading center in the
Scotia Sea with the Shackleton Ridge. Originally we had planned to
deploy the new ITI streamer and balance it in our work area in the
Southwest Scotia Sea but the wind was up to 30 kts and the seas were
building so it was decided to postpone the streamer party until later.
We turned and ran south along the east side of Bridgman Island, neatly
imaging two of the small volcanic cones that Randy Keller and I dredged
on our NBP9301 cruise. We then turned south around the southern edge of
Bridgman Island and headed west into King George Basin.
Bransfield Basin
An initial lowering of the Oregon State vent detection (ZAPS) sled was
made in the eastern end of King George Basin. We then turned southwest
and began to profile the Central Bransfield Basin. The detail of the
Seabeam image is astounding. We have a beautiful image of the submarine
volcano just off Maxwell Bay, King George Island. We then returned to
the eastern end of the King George Basin and made a second ZAPS sled
lowering after which we made a second survey to the southwest. We
picked up numerous small volcanic features, all of which seem to be
lineated and parallel along about four lines. The lineation of these
features is truly remarkable. After additional lowerings of the ZAPS
sled and the CTD rosette we have now proceeded to the Eastern
Bransfield Basin where we are in the process of running a Seabeam
survey towards Clarence Island.
Larry Lawver and the Shipboard Scientific Party
Jackson School of Geophysics»
Note: The photos and journals
contained in this website were prepared by Steven Stevenoski, Science
teacher at Lincoln High School in Wisconsin Rapids, Wisconsin