Geology. Козлова Е.П. - 42 стр.

         We know of deposits formed by sediments accumulated in the water medium.
These are rock and potash salts, phosphorites, manganese ores, combustible shales,
along with limestone, marl and sand which are used as building materials.
         Extant deposits are often acted upon by high temperature and pressure. Then
rock and substances they contain undergo significant modifications: quartz sand and
sandstone turn into hard quartzites, limestone becomes marble, and granite, acquiring
a striated structure, transforms into gneiss. And so some ore bodies vanish without a
trace, while others are modified, and still others are enriched. The metamorphic
mountain rocks thus formed become ore-bearing.
          Conversely, native material on the surface of our planet is subject to
degradation too as a result of water erosion. Water washers off various substances
from the terrestrial surface and takes them away, either dissolved or suspended. The
newly formed minerals often have a negative effect on the environment, as in the case
of weathering and wind erosion: gaseous and readily soluble compounds, once they
get into the hydrosphere and the atmosphere, do harm living organisms. Furthermore,
carbon dioxide as well as compounds of sulfur, methane and ammonia affect the
climate on a local and global scale. Soil, and surface and subsurface water are
contaminated with toxic oxides and complex compounds which have a dire action on
the environment and, penetrating trophic (food) chains, ultimately get into the human
organism.
       Consequently, weathering and erosion processes are playing a dual role. On the
one hand, they are involved in the formation of useful deposits and, on the other, they
have a negative affect on the vital activity of organisms. Both effects have manifested
them-selves throughout the geological history of our planet. And what concerns
biota: erosion, while impairing some groups of organisms, is helpful for the
development of others. All that is in the scheme of things.
       Human civilization has brought about dramatic changes in the situation on the
earth’s surface. The period of accumulation of lithospheric resources, which took
nearly 4 billion years, gave way to open-ended consumption, which has been on for
several thousand years now. Humankind has been actively transforming the
lithospheric surface.

                      Geodynamic Function of the Lithospere

       Destructive natural processes may be sluggish and imperceptible in their
course; but now and then they may come like a bolt from the blue and wreak havoc.
       The slow course of geological changes in the lithosphere and surrounding
mantles can be broken both by natural and by anthropogenic factors; both have
internal (endogenic) and external (exogenic) causes. Say, disastrous events like
volcanic eruptions; earthquakes and emanation of gases from the earth’s interior are
caused by planetary and cosmic factors, that is they are due to inherent, endogenic
causes. Now we know it for certain: regions of eruptive and seismic activity are
confined to lithospheric plate interfaces. The extension and the convergence or
collision of plates interfere with the shell integrity. The faults thus formed are an
opportune escape route for plutonic magma-its flows force their way up to the surface
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