reason for pursuing undersea exploration is our basic curiosity, which drives many
of us to want to penetrate what could be considered as being the last frontier of
planet Earth.
Early oceanographic expeditions, before and at the turn of the twentieth century, were more concerned about the water mass rather than the sea floor itself.
Biological and physical oceanographic investigations were the main concern of the
scientific community. Modern oceanographic expeditions started at the end of the
Second World War and have continued because the world’s industrialized nations
have considerably invested in ocean floor exploration.
What triggers Earthquakes? Why do volcanoes erupt? It is by understanding the
processes taking place on the sea floor that we will have more knowledge of our
planet and this will also help us better understand the extraterrestrial bodies of our
Universe. Since volcanic activity is far greater on the ocean floor (see Chap. 2),
this makes it an ideal place for studying and understanding the mechanisms of
creation and subsequent destruction of the lithosphere-crust. This is primordial
information if we want to learn about the history of our planet.
Bathymetric Mapping and Sea Floor Imagery
Modern Oceanography began with the British deep-sea expedition on board the
H.M.S Challenger, when, under the leadership of Sir Wyville Thomson, men first
scientifically explored the Pacific, Atlantic and Indian Oceans. The earliest
attempts to ‘‘sound the depths’’ (i.e. measure the depth of the oceans) occurred
during the H.M.S Challenger expedition between 1872 and 1876 (Linklater 1972).
The crew used a hemp rope about 2 cm thick, which they dropped over the side as
a depth-gauge. The first bathymetric charts were made through the initiative of
Prince Albert the 1st of Monaco in 1905 and Georg Wüst (1964) published the first
bathymetric chart of the Atlantic Ocean in 1935.
Any manned-submersible exploration must begin with precise mapping of the
sea floor. For today’s mapping of the sea floor, modern technology uses underwater acoustic sound propagation. Sound is generated by explosive devices such as
air or water guns as well as by real explosives (TNT) giving rise to sound
impulsion received by electric amplifiers (hydrophones). The ‘‘sonar’’ (acronym
for Sound Navigation and Ranging) is an instrument that emits ultrasound waves
(pulses of inaudible sounds) and then listens to the echoes of these waves as they
hit any targets on the ocean floor or in the water column. This is a technique that
was developed after determining the effects of sound propagation within water for
determining the depth of the sea floor.
Sound waves differ from radio waves and light waves because they have a
lower frequency and they can propagate in the water column along great distances,
at a speed of about 1500 m/s. Sound waves are then reflected by any obstacles
encountered and are received on the surface ship by means of hydrophones, which
are receivers used to hear the sound wave’s signal. Knowing the amount of time
54
3 Diving into the Abysses
of us to want to penetrate what could be considered as being the last frontier of
planet Earth.
Early oceanographic expeditions, before and at the turn of the twentieth century, were more concerned about the water mass rather than the sea floor itself.
Biological and physical oceanographic investigations were the main concern of the
scientific community. Modern oceanographic expeditions started at the end of the
Second World War and have continued because the world’s industrialized nations
have considerably invested in ocean floor exploration.
What triggers Earthquakes? Why do volcanoes erupt? It is by understanding the
processes taking place on the sea floor that we will have more knowledge of our
planet and this will also help us better understand the extraterrestrial bodies of our
Universe. Since volcanic activity is far greater on the ocean floor (see Chap. 2),
this makes it an ideal place for studying and understanding the mechanisms of
creation and subsequent destruction of the lithosphere-crust. This is primordial
information if we want to learn about the history of our planet.
Bathymetric Mapping and Sea Floor Imagery
Modern Oceanography began with the British deep-sea expedition on board the
H.M.S Challenger, when, under the leadership of Sir Wyville Thomson, men first
scientifically explored the Pacific, Atlantic and Indian Oceans. The earliest
attempts to ‘‘sound the depths’’ (i.e. measure the depth of the oceans) occurred
during the H.M.S Challenger expedition between 1872 and 1876 (Linklater 1972).
The crew used a hemp rope about 2 cm thick, which they dropped over the side as
a depth-gauge. The first bathymetric charts were made through the initiative of
Prince Albert the 1st of Monaco in 1905 and Georg Wüst (1964) published the first
bathymetric chart of the Atlantic Ocean in 1935.
Any manned-submersible exploration must begin with precise mapping of the
sea floor. For today’s mapping of the sea floor, modern technology uses underwater acoustic sound propagation. Sound is generated by explosive devices such as
air or water guns as well as by real explosives (TNT) giving rise to sound
impulsion received by electric amplifiers (hydrophones). The ‘‘sonar’’ (acronym
for Sound Navigation and Ranging) is an instrument that emits ultrasound waves
(pulses of inaudible sounds) and then listens to the echoes of these waves as they
hit any targets on the ocean floor or in the water column. This is a technique that
was developed after determining the effects of sound propagation within water for
determining the depth of the sea floor.
Sound waves differ from radio waves and light waves because they have a
lower frequency and they can propagate in the water column along great distances,
at a speed of about 1500 m/s. Sound waves are then reflected by any obstacles
encountered and are received on the surface ship by means of hydrophones, which
are receivers used to hear the sound wave’s signal. Knowing the amount of time
54
3 Diving into the Abysses