Restless Energy
133
be calculated and warning broadcasts issued. An early warning
system requires networks of seismographs to register the earth
tremors and tide gauges to show any abnormal wave activity. After
the Hawaiian tsunami of 1946, the United States Coast and Geodetic
Survey set up such a system with headquarters appropriately in
Honolulu. japan has a local warning system tied in with that of the
United States, and the Soviet Union has a local warning system for
the Kamchatka Peninsula in Siberia. In addition to local warning
systems, an international centre now exists to alert nations situated
around the Pacic Basin.
Fortunately, serious tsunamis do not occur frequently and most
people are far more familiar with the waves which beat unceasingly
against the shore. In fact, the sound of the surf and the cries of gulls
is all most people need to take them back to memories of holidays by
the sea. Although breaking waves and surf result from the shallow—
ing of the sea bed as the shore line approaches, the energy driving
them originates many miles away in the open ocean. Here prevailing
winds ‘rubbing against the surface of the water’ raise ripples which
under the continuing supply of energy build up into waves. How
big the waves nally become depends upon the strength of the wind,
the time for which the wind blows and the extent of water over which
the wind blows without interruption, known as the ‘fetch’. Probably
one of the highest waves recorded (r 12 feet), Which struck the
United States Navy tanker Ramapo en route from Manila to San
Diego in 1933, occurred in a storm where the wind had an un—
obstructed fetch of thousands of miles. However, as the waves move
away from the direct inuence of the winds that raised them, the
crests become lower and the waves more regular, resulting nally in
the long low waves of the oceanic swell. This can travel thousands of
miles to distant shores with very little loss of energy.
Because the swell originates out in the ocean, it is quite indepen—
dent of winds occurring in other areas. Nevertheless, local winds do
inuence the sea and can create wind—waves which in turn help to
determine the state of the sea. In 1808 a British admiral, Sir Francis
Beaufort, devised a scale of wind forces and, although he used as his
yardstick the area of sail which a fully rigged frigate of the period
could carry, the Beaufort Scale is still in everyday use. A list of
descriptions, approved by the World Meteorolog‘ical Organization,
has been added so that wind forces can be estimated by reference to
the appearance of the sea:
133
be calculated and warning broadcasts issued. An early warning
system requires networks of seismographs to register the earth
tremors and tide gauges to show any abnormal wave activity. After
the Hawaiian tsunami of 1946, the United States Coast and Geodetic
Survey set up such a system with headquarters appropriately in
Honolulu. japan has a local warning system tied in with that of the
United States, and the Soviet Union has a local warning system for
the Kamchatka Peninsula in Siberia. In addition to local warning
systems, an international centre now exists to alert nations situated
around the Pacic Basin.
Fortunately, serious tsunamis do not occur frequently and most
people are far more familiar with the waves which beat unceasingly
against the shore. In fact, the sound of the surf and the cries of gulls
is all most people need to take them back to memories of holidays by
the sea. Although breaking waves and surf result from the shallow—
ing of the sea bed as the shore line approaches, the energy driving
them originates many miles away in the open ocean. Here prevailing
winds ‘rubbing against the surface of the water’ raise ripples which
under the continuing supply of energy build up into waves. How
big the waves nally become depends upon the strength of the wind,
the time for which the wind blows and the extent of water over which
the wind blows without interruption, known as the ‘fetch’. Probably
one of the highest waves recorded (r 12 feet), Which struck the
United States Navy tanker Ramapo en route from Manila to San
Diego in 1933, occurred in a storm where the wind had an un—
obstructed fetch of thousands of miles. However, as the waves move
away from the direct inuence of the winds that raised them, the
crests become lower and the waves more regular, resulting nally in
the long low waves of the oceanic swell. This can travel thousands of
miles to distant shores with very little loss of energy.
Because the swell originates out in the ocean, it is quite indepen—
dent of winds occurring in other areas. Nevertheless, local winds do
inuence the sea and can create wind—waves which in turn help to
determine the state of the sea. In 1808 a British admiral, Sir Francis
Beaufort, devised a scale of wind forces and, although he used as his
yardstick the area of sail which a fully rigged frigate of the period
could carry, the Beaufort Scale is still in everyday use. A list of
descriptions, approved by the World Meteorolog‘ical Organization,
has been added so that wind forces can be estimated by reference to
the appearance of the sea: