Geoscience Reference
In-Depth Information
Chapter 1
Omnipresent Soils
Knowledge of our Homo sapiens existence is restricted to a tiny patch of both space
and time in the cosmic infi nity. In spite of the presence of such infi nite dimensions
and our feelings of being isolated, lost, and completely out of touch with all other
vast, unknown reaches within and outside the universe, it will help us to put parts of
our known world into mutual relationships. Our soils form a very thin peel on the
surface of our planet Earth. The total surface area of Earth is 510 million km 2 or
5.1 × 10 8 km 2 . Real soils have been born on terrestrial landscapes that extend across
143,330,000 km 2 or rounded to 1.43 × 10 8 km 2 when we omit the area of Antarctica
covered by ice during the last 2 million years. The surface area of all planets in our
solar system, rounded to 1.22 × 10 11 km 2 , is roughly 3 orders of magnitude larger
than the area of all our continents and islands, again without Antarctica. Or, in other
words, the soil covering our Earth's solid surface is a thousand times smaller than
the surface areas of all planets in our solar system.
The size of the surface area of all soils on our planet Earth is not a single fascinat-
ing property. There are countless processes running in that thin peel that they remind
us of numerous functions running in the skin of living bodies. The comparison of
soil to the skin of animals was for the fi rst time used in 2005 by Alfred Hartemink,
Secretary General of the IUSS, in the brochure prepared for the occasion of the
International Year of Planet Earth. The booklet's title was Soil - Earth's living skin.
It is stated there that without soil the Earth's landscape would be as barren as Mars.
Awed by the parable soil - skin , we modifi ed it in our topic's title.
Soils evolved on Earth's continents having two specifi c properties, both of which
are diffi cult to grasp and fully appreciate in terms of our everyday and lifetime expe-
riences. One is the extremely large surface area of solid particles within the soil,
e.g., if we measure it in the top 30 cm of soil below a land surface area of 1 m 2 , we
obtain an average value of about 10 6 -10 7 m 2 . It is the size of about a square kilome-
ter or even more. The second soil property is the magnitude and importance of the
hollows between the solid particles called soil pores. These pores usually occupy
about 50 ± 10 % of the total soil volume and have sizes ranging between tens of
nanometers up to hundreds of micrometers. The volume of millimeter-sized pores is
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