Geography. Козлова Е.П. - 92 стр.

                                       17.10 Tides

      The term tide is applied to the periodical rising and falling of the water of the
ocean caused by the attraction of the sun and moon. Periodical alterations in the
direction of the wind, and periodical variations in atmospheric pressure, may give rise
to alterations in the level of the sea, but true tides are attributed (are due to) to
astronomical causes. It is supposed that the attraction of the sun and moon may affect
not only the waters of the ocean but also the solid crust of the earth, producing an
alternating change in its shape, but so small as to be difficult of detection.
      Anyone living at the seaside must have observed the gradual advance and retreat
of the sea about twice in the 24 hours, or to be more exact, twice in 24 hours 50
minutes, the average interval between two successive high waters being 12 hours 25
minutes. The time of high-water thus changes from day to day, and is evidently
related to the position of the moon, which passes the meridian on an average 50
minutes later on each succeeding day. The height to which the water rises varies also
from day to day, the range from high-water to low-water being greatest about the
time of full moon and new moon, when the tides are called “spring-tides”, and least
about the time of the moon’s first and third quarters, when the tides are called “neap-
tides”. The tide generating effect of the moon is more than double that of the sun,
because of the very much greater distance of the sun, in spite of its greater mass.
When the sun and the moon are both on the same side of the earth and when they are
diametrically opposed to each other their tide-generating effects are additive, but
when they are at right angles to each other the effects are subtractive, so that the
spring-tides have a range three times greater than the neap-tides.

                                      17.11 Eurasia

      The origin of the largest of the continents-Eurasia – goes to the very beginning of our
planet. Basically, it was represented by an archipelago of giant islands, rising above the
surface of the vast seas which then covered much of the world. These islands were five in
number: the Scandinavian shield in the northwest; the Siberian shield, largest of all, in the
north; the Chinese shield in the east; the Thailand – Cambodjian in the southeast; and the
Indian shield in the south.
      The seas above which these islands rose in these earliest days of the earth’s
formation have disappeared, but two of them, the Tethys and the Uralian existed for so
long that they played an important role in the history of Old World flora and fauna.
      The Tethys was the southern of these two enormous bodies of water: it reached from
the Alps and the Mediterranean basin all the way to the Timor Sea in the Indonesian
archipelago, covering the entire width of southern Asia, Turkey, Iran, the Himalayas and
Vietnam. Its shorelines changed during the more than 560 million years of its existence.
Some 36 million years ago the Tethys began to dry up, eventually leaving behind it some
of the familiar contours of the lands we know today. Great upheavals of the earth’s crust
gave rise to the Alps and the Himalayas, isolated its entire central area, and the two ends
of this enormous sea became separated by thousands of miles of emerged land.
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