Ill. BATHYMETRY OF THE SOUTH SANDWICH TRENCH 
During DEEP FREEZE 1961 operations, GLACIER obtained three sonic depth 
profiles across the South Sandwich Trench, in the vicinity of METEOR DEEP. Profiles 
were recorded with an AN/UQN-1B echo sounder. Noise level resulting from high 
seas reduced the clarity of the record to such an extent that depths could be scaled 
only to the nearest 50 fathoms. Navigational errors were small when radar was used. 
When navigation was by celestial fix or dead reckoning errors of 5 miles or greater 
were encountered. Velocity corrections were applied to all soundings to bring them 
to the same datum as the METEOR soundings. 
The South Sandwich Islands, emergent parts of the Scotia Ridge, are portions of a 
Pacific-type island arc system extending from the tip of South America to Antarctica. 
The South Sandwich Trench lies along the convex side of this arc from South Georgia 
Island to near the South Orkney Islands. The location of the southern extent of the 
trench is somewhat doubtful because of the paucity of sounding data in the area. 
Figure 26 is a general bathymetric chart of the southwestern Atlantic Ocean, showing 
suggested topographic and geographic relationships between the South Sandwich Trench 
and the surrounding topographic features. 
Data presented in Figure 26 and a survey of literature (Jacobs, et al, 1958 and 
Guilcher 1958) indicate that the South Sandwich Trench is an arcuate Trench, the 
outer convex feature of a primary arc. This arc and others similar to it in plan, but 
varying in complexity of structure, constitute the great continental fracture system - 
two major orogenic belts which encircle the earth in a scalloped linear pattern. The 
South Sandwich Islands chain is a good example of an active primary island arc. This 
arc differs from other arcs in the system in that it is reversed in orientation to the ad- 
jacent arcs of the Chilean Cordillera and Palmer Peninsula of Antarctica. An analo- 
gous structure of this type is the reversed arc of the Lesser Antilles Islands . 
In both the Lesser Antilles and the South Sandwich Islands, great transcurrent 
faults extend in an east-west direction for a considerable distance from the ends of 
the island arc to the main orogenic belt. A corresponding gap equal in length to 
the island arcs is left in the fracture system (Fig. 26). Similar topographic align- 
ment occurs along the transcurrent fault zones of the Lesser Antilles structure, with 
Cuba and the Greater Antilles forming the northern boundary and the north coast 
of Venezuela the southern boundary . 
The arrows in Figure 26 show the probable direction of movement of the earth's 
crust along the topographic alignment of the South Sandwich Trench. Earthquakes 
and active volcanism throughout these zones indicate that movement might still be 
46 
