Water is necessary for all life, as well as for human
agriculture and industry. Great e_ort and expense has
gone into diverting water from where it occurs
naturally to where people need it to be. The large -scale
redistribution of such a v
Minerals are everywhere around us. For example, the
ocean is estimated to contain more than 70 million
tons of gold. Yet, it would be much too expensive to recover
that gold because of its very low concentration
in the water. Minerals mus
ECONOMIC VALUE OF
Minerals that are of economic value can be
classi_ed as metallic or nonmetallic. Metallic
those from which valuable metals (e.g. iron,
copper) can be extracted for commercial use.
are considered geochemi
The earth's crust is composed of many kinds of rocks, each
of which is an aggregate of one or more minerals.
In geology, the term mineral describes any naturallyoccurring solid substance with a speci_c composition
and crystal structu
Minerals are not evenly distributed in the earth's crust.
Mineral ores are found in just a relatively few
areas, because it takes a special set of circumstances to
create them. Therefore, the signs of a mineral
deposit are often small
MINERAL SUFFICIENCY AND THE
Mineral resources are essential to life as we kno w it. A
nation cannot be prosperous without a reliable source
of minerals, and no country has all the mineral resources it
requires. The United States has about 5 percent
Soil can take hundreds or thousands of years to mature.
Therefore, once fertile topsoil is lost, it is not easily
replaced. Soil degradation refers to deterioration in the
quality of the soil and the concomitant reduction
in its capacity
SOIL FERTILITY AND pH
There are 16 elements essential for plant growth. Plants
obtain three of them primarily from air and water:
carbon, hydrogen and oxygen. The other 13 elements
generally come from the soil. These essential elements
for plant growth ca
Most soil consists of weathered inorganic rock material.
The relative amounts of di_erent sizes and types of
rock particles or grains determines the texture of the soil.
The three main types of rock grains found in soil
are: sand, sil
Soil plays an important role in land ecosystems. In order
for a community of producers and consumers
to become established on land, soil must be present.
Furthermore, soil quality is often a limiting factor
for population growth in ecos