|
Because of the tremendous pressure, the depth to which a diver can
descend without special equipment is severely limited. The deepest
recorded dive by a skin diver is now 170 meters (558 ft), set on
October 12, 2003, by Pipin Ferraras. The deepest recorded dive by
a scuba diver was made by Australian John Bennett at 308 meters
(1,010 ft).
Revolutionary
new diving suits, such as the "Jim suit" shown below,
enable divers to reach depths up to about 600 meters (2,000 ft).
Some suits feature thruster packs that can boost a diver to different
locations underwater.
 Courtesy
of NOAA
To
explore even greater depths, deep-sea explorers must rely on specially
constructed steel chambers to protect them. In 1934, American oceanographer
William Beebe and engineer Otis Barton were lowered to about 1,000
meters (3,280 ft) in a round steel chamber called a bathysphere,
which was attached to a ship on the surface by a long cable. During
the dive, Beebe peered out of a porthole and reported his observations
by telephone to a colleague, Miss Hollister, on the surface.
In
1948, Swiss physicist Auguste Piccard began testing a much deeper-diving
vessel he invented called the bathyscaphe. (This word is
derived from the Greek words bathos — "deep"
and scaphos — "ship.") On an unpiloted dive
in the Cape Verde Islands, his invention, named FNRS 2, successfully
withstood the pressure on it at 1,402 meters (4,600 ft), but its
float was severely damaged by heavy waves after the dive.
In the 1950s, Jacques Piccard joined his father in building new
and improved bathyscaphes including Trieste, which dived
to 3,139 meters (10,300 ft) in field trials. The U.S. Navy acquired
Trieste in 1958 and equipped it with a new cabin to enable
it to reach deep ocean trenches. In 1960, Jacques Piccard and Navy
Lieutenant Donald Walsh descended in Trieste to the deepest
known point on Earth — the Challenger Deep in the Mariana Trench.
The two men made the deepest dive in history: 10,915 meters (35,810
ft).
Today,
scientists are making exciting discoveries about the ocean floor,
thanks to deep-sea submersibles such as Alvin. Operated by
the Woods Hole Oceanographic Institution in Massachusetts, this
three-person sub made its first dive in 1964. Since then, Alvin
has made more than 3,700 dives to an average depth of 2,068 meters
(6,785 ft).
Alvin
has conducted a wide variety of research missions, from discovering
giant tubeworms on the Pacific Ocean floor near the Galápagos
Islands, to surveying the wreck of HMS Titanic in the Atlantic
Ocean.
Alvin
has met some amazing life on its travels, but so far it has not
encountered one of the deep sea's most mysterious inhabitants —
the elusive giant squid. However, Alvin once was attacked
by a swordfish, which became trapped between two pieces of the sub's
fiberglass skin. The fish was brought back to the surface and cooked
for dinner!
|
|
|
 |
| Inventor
Salim Joseph Peress's diving suit, "Tritonia," with its
reticulated joints (left), explored the wreck of the Lusitania in
1937. The novel diving gear was the forerunner of the "Jim suit."
Photo courtesy of NOAA. |
Throughout
history, scientists have relied on a number of specialized tools to measure,
map, and view the ocean's depths. These are a few highlights.
One
of the first instruments used to investigate the sea bottom was the sounding
weight. Viking sailors took measurements of ocean depth and sampled
seafloor sediments with this device, which consisted of a lead weight
with a hollow bottom attached to a line. Once the weight reached the ocean
bottom and collected a sample of the seabed, the line was hauled back
on board ship and measured in the distance between a sailor's outstretched
arms — a 1.83-meter (6 ft) unit called a fathom.
This term is still used today for nautical depth.
Cornelius
van Drebel, a Dutch inventor, is credited by many historians with building
the first submarine. His underwater vessel consisted of a wooden frame
sheathed in leather. Oars extending out the sides propelled the craft
through the water, at depths up to 4.6 meters (15 ft). The oar openings
were sealed with tight-fitting leather flaps. Drebel tested the sub in
the Thames River in England between 1620 and 1624. King James I is said
to have taken a short ride in the craft.
From
1872 to 1876, a landmark ocean study was undertaken by British scientists
aboard HMS Challenger, a sailing vessel that was redesigned into
a laboratory ship. The Challenger expedition covered 127,653 kilometers
(68,890 nautical miles) and is credited with providing the first real
view of major seafloor features such as the deep ocean basins. The researchers
used wire-line soundings to determine depths and collected hundreds of
water, sediment, and biological samples from all the oceans except the
Arctic. They discovered more than 4,700 new species of marine life, including
deep-sea organisms.
 |
|
This
is how Atlantis launches the submersible Alvin.
|
Deep-sea
exploration advanced dramatically in the 1900s with a series of inventions,
ranging from sonar — a system for detecting the presence of objects
underwater through the use of sound — to manned deep-diving submersibles
such as Alvin.
Owned
by the U.S. Navy and operated by the Woods Hole Oceanographic Institution,
Alvin can carry a crew of three to depths of 4,500 meters (14,764
ft). The sub is equipped with lights, cameras, computers, and highly maneuverable
arms for collecting samples in the darkness of the ocean's depths.
|
| The
sub Alvin, with a crew of two sicientist and a pilot, begins
its descent to the seafloor. |
|
However,
the voyage to the ocean floor takes time in a submersible — it's
a long, cold trip to hydrothermal vent sites 2.4 kilometers (1.5 mi) below
the surface — and scientists are working to find ways to observe
this extreme environment without being in it. With the expanded use of
fiber optics and robotics, scientists hope to someday explore the deep
sea from a computer screen in the lab rather than out of a porthole.
In fact, a team of researchers from several U.S. and Canadian institutes
is now in the design phase of "Project Neptune," a bold plan
for installing remote-controlled instruments across Juan de Fuca Plate,
a tectonic plate that lies off Canada, the Pacific Northwest, and California.
The project is expected to be in operation by 2006.
|
 |
