in certain areas. Such approaches are as applicable 
underwater as ashore. 
4. Geological 
Confirmation of the actual minerals present can 
be accomplished only by sampling and subsequent 
analysis. Methods of direct observation on-site are 
limited in usefulness to such items as outcrops, 
type of bottom (sand, mud, etc.), and nodules. 
Methods of direct observation include those by 
divers and observers in deep submersible vehicles. 
Deep towed vehicles provide indirect continuous 
monitoring by television and by still and motion 
picture photography. Observation supplemented 
by bottom sampling is the most likely method of 
evaluating occurrences of manganese nodules on 
the sea floor by estimating area coverage, nodule 
size, and shape. 
Because of the overriding importance of coring, 
major emphasis should be given to techniques for 
taking more samples and deeper cores. Coring 
provides samples for chemical and mineralogical 
analysis. 
Much sampling today employs conventional 
tools originally developed for oceanographic re- 
search. Excluding core drilling systems, many 
bottom sampling devices cannot probe deeper than 
about 20 feet, although cores of up to 90 feet have 
been taken in very soft sediments. More recently, a 
vibratory corer has been developed that can take a 
100-foot core six inches in diameter. This has 
proven very useful in evaluating mineral concentra- 
tions on the shelf. 
Commonly used sampling devices are: 
—Free fall grab sampler—useful for deep nodules. 
—Wireline dredge samplers—used since the Chal- 
lenger days; the disadvantage of dredging proce- 
dures is the lack of knowledge concerning the 
exact location of the sample. 
—Free fall corers—cannot penetrate rock or gravel; 
remote controlled rotary corers powered and 
controlled from a mother ship, will enable obtain- 
ing short cores from rock. 
—Jet lift corer—using water or air pumped down a 
pipe. 
—Vibratory corer—newest type developed. 
Petroleum core drilling systems with steel bits 
penetrate softer rock to 20,000 feet. Small dia- 
meter diamond core drills have penetrated harder 
rock to about 14,000 feet, although most conven- 
tional rigs are equipped to penetrate 4,000 or 
4,500 feet. 
5. Shipboard Integrated Survey Systems 
Shipboard integrated geophysical systems have 
become available recently, including automatic 
sensing and recording devices. These measure 
simultaneously many parameters from magnetom- 
eter, gravimeter, echo sounder and seismic readings 
with reference to a synchronous clock, navigation 
fixes, and ship’s course and speed. The data can be 
produced in both analog and digital form, includ- 
ing recordings on magnetic tape, for computer 
processing often while still underway. 
6. Required Supporting Technology 
Aside from ships currently used for mineral 
survey work, the role of submersibles is beginning 
to be appreciated. Newer versions will have 
greater depth and cruising range capabilities, per- 
mitting them to survey and sample. As an ex- 
ample, the Alvin has been used to recover sea floor 
specimens and perform geological studies in the 
West Indies and near Woods Hole. 
An accurate navigation fix is critical in undersea 
prospecting, and as the search becomes more 
detailed, less error in positioning can be tolerated. 
The tolerable error also depends on the distribu- 
tion of the mineral deposits. When distribution is 
broad and uniform, positioning requirements for 
exploitation are reduced, and at least initial 
exploitation will be little concerned with precise 
positioning. If distribution is patchy and concen- 
trations are localized, precision positioning is 
essential both for evaluating deposits and for 
exploiting them efficiently. 
D. Recovery 
1. Dredging 
Onshore placers and other various unconsoli- 
dated deposits have been exploited commercially 
for many years throughout the world. Underwater 
mining recovery can presently be accomplished for 
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