What's it like at the bottom
of the ocean? That depends on what ocean you're talking about and
exactly where on that ocean you happen to be located.
If you are over:
- the Mariana Trench in
the North Pacific, the depth will be 35,800 feet.
- the TongaKermadec Trench
in the South Pacific, the depth will be 34,876 feet.
- the Puerto Rico Trench
in the North Atlantic, the depth will be 27,500 feet.
- the Sandwich Trench
in the South Atlantic, the depth will be 27,144 feet.
These statistics are impressive
if you consider that Mount Everest, the tallest mountain in the world,
is 29,028 feet high.
Let's establish some basic
concepts. The ocean contour is divided into three domains: the continental
shelf, the continental slope, and the deep ocean basins. The average
depth of the sea floor is 4,000 meters Cone meter + 3.28 feet).
The abyss of the oceans
is characterized by intense cold, 0.6 C to 3.5 C (water freezes at
O C), no light, and lots of pressure. The tremendous pressure is due
to the weight of the water column at the particular depth you happen
to be measuring. As you proceed down, the pressure increases 15 pounds
per square inch for every 30 feet. Spend a few minutes with your pocket
calculator estimating the pressure at each of the great depths of
the oceans mentioned above.
At these great depths,
the pressure can equal about 8 tons per square inch and that pressure,
because of the liquid nature of water, is exerted in all directions.
One would think that nothing could live in this extremely hostile
environment. But research has proven this to be untrue. Creatures
with names such as the whip tail gulper eel, sea cucumber, grenadier
or rattail fish, a host of marine isopods, and the glass sponge, Eupleetella
asperfillum, live down there. There is an intriguing story connected
with this species of glass sponge. An abyssal shrimp enters into the
sponge's hollow interior and, after feeding on the food the sponge
takes in, grows too large to escape. The shrimp is doomed to a life
of captivity within the sponge. In Japan, these sponges, with their
imprisoned shrimp, were once given as wedding presentssymbols
of everlasting matrimonial union.
What is the bottom of these
depths really like? The answer is ooze! Not the kind you associate
with the muddy bottom of a pond or saltwater marsh. It's a grayish,
yellowish, tarnish ooze. A handful soon makes it apparent that it
is butterlike, slippery, and mighty cold. With such attractive qualities,
what use can it have for mankind? Ooze is composed of particles of
sediments, the dead bodies of microscopic plankton which, year after
year, eon after eon, fall to the bottom. These age-old sediments are
a help to scientists. Over the millions of years that these sediments
have been falling, the "snowfall" has deposited a biological
history of life in the ocean. There are several kinds of ooze, each
with its "index fossils." Certain fossils are keys to geological
periods in the earth's history, thus, their presence offers the scientist
an index of life that existed during a certain time. This fossil record
also tells much about the age of the abyssal deposits.
Briefly, there are four
types of ooze: red clay, globigerina ooze, radiolarian ooze, and pteropod
ooze. Each kind of ooze is made of different substances and seems
to be specific, to a certain degree, to various parts of the earth's
oceans. Petroleum industry scientists are most interested in reading
geologic history in these oozes, for certain types are more apt to
be oilbearing than others, while other types may be harder or softer
to drill through. Scientists who study these fossils are called micro
paleontologists (micro, "small"; pale, from the Greek "palai,"
meaning "ancient, old in years").
In 1977, some very interesting
discoveries were made on the deep ocean floor 500 miles off the coast
of Ecuador and 215 miles east of the Galapagos Islands. Drs. Robert
Ballard and Fred Grassle, of the Woods Hole Oceanographic Institution,
descended to the Galapagos Rift, a rugged split in the ocean floor.
There, in the minisub Alvin, 2,500 meters beneath the surface and
subjected to pressures of more than 3,650 pounds per square inch,
these men discovered new forms of life. On this rough, dark seascape
they found that warm water, heated from the earth's core, was erupting
to the earth's crust. The warm springs, called "hydrothermal
vents," changed the surrounding water (at 2°C) to temperatures
that approached 10 to 15°C. On and near these vents they found worms,
footlong clams, mussels, and crabs. Perhaps most fascinating was a
lovely orange creature with long filamentsthey called it "dandelion"
for its strong resemblance to the flower. How could these animals
exist at that depth, with no sun, and therefore no plant life on which
to feed? Research found the answer chemosynthesis (chemo, "chemical";
synthesis, "making from") held the clue. The deep ocean
bacteria, always present and a potential food source, were being nourished
by a chemical synthesis of hydrogen sulfide (the gas that smells like
rotten eggs) and other substances in the heated water that issued
from these vents. Thus, the bacteria grew and became food for the
mussels and clams. The "dandelion" upon further study proved
to be a colony of organisms related to the Portuguese manofwar and
belonging to the family Rhodaliidae (from the Greek "rhodon,"
"a rose"; hence, red). Perhaps of equal interest were the
large red tube worms belonging to the family Vertimentiferan (vert,
from the Latin "vertex," meaning "twining, whirling").
These worms had attained lengths of up to three metersabout 9.8 feet
The oceanic world gives
up its secrets reluctantly and not without much effort on the part
of man. There is still a great deal to be learned from the abyss.
Such study will exact a great deal of research and planning on the
part of those who will venture into this world of cold, pressure,
and eternal darkness.
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