E. A. Abdalina, R. J. Hoshimova

X. Answer the following questions after reading the text given below

1. 
   What is the difference between surface water and ground water?
   
2. 
   How does the ground water influence the process of oxidation?
   
3. 
   Is there any underground water beneath the ocean?
   

GROUND WATER

Ground water is the water contained underground in the interstices of soil and rock. When rain falls on the earth some evaporates, some is absorbed by plants, more runs off in streams and the remainder sinks into the earth to become ground water. The amount that enters the ground depends on various factors: rain falling on loose soil sinks immediately; rain falling on clay either lies in the surface and evaporates or runs off; on steep slopes run off will exceed absorption. Ground water exists everywhere in the earth's crust, generally not much deeper than about a mile.

The upper surface of this water is known as the water table. The height of the water table varies between wet and dry seasons and between humid and arid regions. In deserts the water table may be hundreds of feet below the surface.
The region that is sometimes above and sometimes below the water table is known as the zone of fluctuation. This zone through which the water table fluctuates is the place where decomposition of rock is most active. The relation between the contour of the water table and the topography or contour of the land is well marked. The water table rises to higher levels underneath the hills, and slopes to lower levels in the valleys, where it may appear on the surface in the form of springs, rivers, bogs or lakes; but the slope of the water table is always less abrupt than the slope of the overlying land surface.
This ground water acts directly by taking into solution the soluble minerals (process of solution) and by adding molecules of water to the other minerals (process of hydration), and indirectly by bringing carbon dioxide to be combined with some of the elements in solution, such as calcium, to form carbonates (process of carbonation). Oxygen readily unites with most elements and this combination is present. As a result, we get oxides (process of oxidation).
Thus we see that decomposition of the earth materials is carried on very actively in the presence of ground waters. Since they are always seeking a lower level they may run out of the side of a hill as a spring or feed a stream or lake whose level is an indication of the height of the water table at that particular point. As this water seeps through the cracks, crevices, and holes in the rock beneath us, it takes some of the rock minerals in solution and transports them to lower levels, eventually to rivers that will carry these soluble, minirals on the sea. As this continues for a long period of years, what was originally an interstice or ctack in the rock may be opened into a larger cavity, known as a cave.
Water cycle. Ground waters and surface waters both seep and flow to lower levels until eventually they rich the sea. They are usually laden with materials in solution or suspension, and when flowing as surface waters they may push heavier ricks along on the bottom of the stream. All of this foreign matter is left in the sea. As a result of heat¹ from the sun, the water evaporates into water vapor that is carried hundreds and thousands of miles by air currents until clouds are formed by the condensation of the water vapor about tiny particles, and adisturbance causes precipitation. The falling water goes over and through the ground to the sea, thus repeating the cycle.²