Page 217 - NS-2 Textbook

Seawater: Its Makeup and Movements

Why is the ocean salty? What elements are in water and and placed in a freezer will expand greatly and may split,
in the Nsalts" of the sea? How do waves, ClllTents, and for instance. A glass bottle will shatter as the ice expands.
tides move, and why? If this unique expansion did not take place, ice
People have asked these questions for centuries. would sink in water, causing water to freeze from the
Matthew Fontaine Maury of the u.s. Navy, who is re- bottom up. As V.T€ all know, ho,vever, ice cubes float.
garded as the fOlmder of modern oceanography, greatly More important, ice floats on the surface of the ocean, a
increased our knowledge of the oceans through his stud- lake, or a pond, serving as an insulating barrier and hold-
ies of navigational charting and of cUlTents, "Tinds, and ing the heat in the water below. If this were not so, much
storms from 1842 to 186l. of Earth's oceans would probably be mostly ice most of
Since then, much has been learned about the oceans, the time, and life as we know it might have evolved velY
but "vith each ne\v bit of information} more questions differently.
arise. The seas are not only beautiful and interesting but Another quality of water is its ability to store heat.
also absolutely essential to the very existence of Only ammonia has a greater heat storage capacity than
mankind. In addition to the untold wealth beneath their water. Land, on the other hand, absorbs and loses heat
surface and within their seabeds, the seas make possible quickly. If the globe were all land, like the Moon, it
life itself on our planet. would be scorching hot evelY day and freezing cold
every night. Not many life forms could survive under
these conditions. The vast world ocean} howevel~ acts as
WHAT IS WATER?
an enormous heat-controlling thermostat. It absorbs and
Water is one of the most abundant, widely distributed, loses heat more slowly than the land nearby. Also, be-
and essential substances on the surface of the Earth. It is cause of the great currents in the sea, the ocean can ab-
an essential requirement for the cells of humans, other sorb heat in one area and then transfer it to other areas
animals, plant life, and even crystals of many minerals. where some of that heat is released.
Water has many forms. Ice is water in solid form, clouds Those who live near the seacoasts, or the Great
(and steam) are water in vapor form, and water in liquid Lakes, are well aware of this characteristic of 'vater. In
form can be found in any lake, river, or ocean. summer weather air temperatures are cooler near the
Snow is probably the purest natural source of water. coast than farther inland, where the Sun quickly heats
Rain is next in purity, although both snowflakes and the grolmd. In wintel~ because the water retains heat
raindrops are formed with a tiny nucleus of salt or dust. longer, the exact opposite happens: it is warmer near the
Pure water is a compound of two parts hydrogen and coast and colder farther inland.
one part oxygen. In chemical terms, this is expressed as Except ,mder extreme pressure, such as at great
H 0. Only when water is between the temperatures of 32 ocean depths (or under laboratory conditions), water is
2
degrees and 212 degrees Fahrenheit (0 to 100 degrees not compressible. That is, a given amount of water can-
Celsius) at standard atmospheric pressure is it a liquid. not be made smaller in cubic volume. On the other hand,
this liquid can be stirred or mixed easily, and the mole-
cules will readily associate with each other, retaining its
PHYSICAL BEHAVIOR OF WATER
liquid forn1. This means that water can "turn over," al-
In large part, the special characteristics of water make life lowing the heat from the surface to move into deeper
on Earth possible. For instance, most materials expand depths, colder water to move to the surface, and water to
when heated and contract when cooled. Watel~ hovvever, evaporate from the surface, aided by wind and wave ac-
contracts Imtil cooled to about 4 degrees C (39.2 degrees tion. These processes of absorption and evaporation are
F) but then expands rapidly as it freezes, increasing in vital to the pattern of world climate and to the transfer of
volume about 9 percent. A milk carton filled with water heat from equatorial to polar regions.

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