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Sir John Vanden Bempde Johnstone hired Smith as his land steward in Hackness in 1828. Johnstone was a member of the Geological Society and a fossil collector himself. He was aware of Smith's accomplishments, and with the assistance of a friend, he championed for an annuity to be purchased for the aging geologist.

In 1831 Smith was awarded the first Wollaston Medal by the Geological Society of London in recognition of his research into the mineral structure of the Earth. In return, Smith presented the Society with his original table of 23 strata (1799), his colored geologic map of Bath and the surrounding area (1799), and an original rough sketch of his geologic masterpiece (1801). He received his gold medal the next year followed by a government pension. Trinity College in Dublin awarded him an honorary doctorate degree in 1835.

Smith's last job was serving as part of a committee selected by the government to choose the new building material for the British House of Parliament, as the old building had burned down in 1834. The committee selected a magnesium limestone from a quarry in Derbyshire. The supply ran short, and a quick substitution had to be found. The substitute stone turned out to be unsuitable. one wonders if smith might have recognized this and corrected the error before it was too late, if he had lived longer. Within 10 years, the exterior of the buildings deteriorated.

on the way to a British Association meeting in Birmingham, smith stopped to visit a friend in Northampton. He caught a cold that turned fatal. The father of English geology died on August 28, 1839. he was buried nearby in saint Peter's Church.

smith freely shared his knowledge of England's geology. his geologic maps were practically applied to the fields of mining, agriculture, road building, water draining, and canal building. his 1815 map of England and Wales is considered a milestone in geological cartography. Though smith's major accomplishments went unnoticed by the scientific community initially, smith's contributions to geography and biostratigraphy were just beginning at be recognized at the time of his death. In 1865 the Geological society added smith's name to Greenough's map, rightfully acknowledging his intellectual contribution. The Geological society and the oxford Museum display busts of smith, and signposts and plaques adorn his former residences. since 1977 the society has awarded the William smith Medal for contributions to applied and economic aspects of geology. The man who revealed his vision of the underworld has finally received the recognition he deserves.

See also European geology; stratigraphy, stratification, cyclothem.

FURTHER READING

Phillips, John. Memoirs of William Smith. 1844. Reprint, with additional material by hugh Torrens, Bath, u.K.: Bath Royal Literary and scientific society, 2003. Winchester, simon. The Map That Changed the World. Rockland, mass.: Wheeler, 2001.

soils soils include all the unconsolidated material resting above bedrock and serve as the natural medium for plant growth. Differences in soil profile and type result from differences in climate, the type of the original rock source, the types of vegetation and organisms, topography, and time. Normal weathering produces a characteristic soil profile, marked by a succession of distinctive horizons in a soil from the surface downward. The A horizon is closest to the surface, and usually has a gray or black color because

Peat layer over bedrock in a cliff near Quito, Ecuador (Dr. Morley Read/Photo Researchers, Inc.)

of high concentrations of humus (decomposed plant and animal tissues). The A horizon typically loses some substances through downward leaching. The B horizon is commonly brown or reddish, enriched in clay produced in the same place that the rock it was weathered from was located, and transported downward from the A horizon. The C horizon of a typical soil consists of slightly weathered parent material. Young soils regularly lack a B horizon, and the B horizon grows in thickness with increasing age.

some unique soils form under unusual climate conditions. Polar climates are typically cold and dry, and the soils produced in polar regions are typically well drained and lack an A horizon, sometimes underlying layers of frost-heaved stones. In wetter polar climates, tundra may overlie permafrost, which prevents the downward draining of water. These soils are saturated in water and rich in organic matter. These polar soils play a crucial role in maintaining the global environment. They contain an abundance of organic material, effectively isolating it from the atmosphere and locking up much of the planet's carbon. Cutting down of northern forests as is occurring in siberia may affect the global carbon dioxide budget by releasing much of this organic material as carbon dioxide to the atmosphere, possibly contributing to climate change and global warming.

Dry climates limit the leaching of unstable minerals, such as carbonate, from the A horizon. Leaching may also be impeded by evaporation of groundwa-ter. Extensive evaporation of groundwater over prolonged times leads to the formation of caliche crusts. These are hard, generally white carbonate minerals and salts that were dissolved in the groundwater but precipitated when the groundwater moved up through the surface and evaporated, leaving the initially dissolved minerals behind.

In warm, wet climates, most elements (except for aluminum and iron) are leached from the soil profile, forming laterite and bauxite. Laterites, which are c o

Topsoil (rich in organic matter)

Topsoil (rich in organic matter)

Soil leached of soluble materials; rich in clay and insoluble materials

Little organic matter; dissolved minerals from A-horizon precipitated typically deep red in color, are found in many tropical regions. Some of these soils are so hard that they are used for bricks.

Soils form at various rates in different climates and other conditions, ranging from about 50 years in moderate temperatures and wet climates, to about 10,000 to 100,000 years for a good soil profile to develop in dry climates, such as the desert southwest of the United States. Some mature soils, such as those in the tropics, have been forming for several million years. Deforestation causes soil erosion, which cannot be repaired easily. In many places, such as parts of Madagascar, South America, and Indonesia, deforestation has led to accelerated rates of soil erosion, removing thick soils that have been forming for millions of years. These soils supported a rich diversity of life, and it is unlikely that the soils will ever be restored in these regions.

See also mass wasting;

Bedrock cracked and weathered

© Infobase Publishing

Typical soil profile, showing organic zone, and the A, B, and C horizons weathering.

FURTHER READING

Birkland, P. W. Soils and Geomor-phology. New York: Oxford University Press, 1984.

solar system The Earth's solar system represents the remnants of a solar nebula that formed in one of the spiral arms of the Milky Way galaxy. After the condensation of the nebula, the solar system consisted of eight major planets, the moons of these planets, and many smaller bodies in interplanetary space. From the Sun outward, these planetary bodies include Mercury, Venus, Earth, Mars, the asteroids, Jupiter, Saturn, Uranus, and Neptune. The physical properties of these bodies are listed in the table "Physical Properties of Objects in the Solar System." Until 2006 Pluto was regarded as a planet, but in 2006 a team of astronomers voted that Pluto did not meet the criteria of being a planet in that its orbit was too erratic and its size too small, and demoted Pluto to the status equivalent of a captured asteroid. Most asteroids are concentrated in a broad band called the asteroid belt located between the orbits of Mars and Jupiter. Although none of the asteroids are larger than the Earth's moon, they are considered by many to be "minor planets," since they are orbiting the Sun.

The asteroids are small rocky, metallic bodies, most of which orbit in the asteroid belt located between Mars and Jupiter, although some have different erratic orbits. Others are located in different belts further from the Sun. Comets include icy bodies and rocky bodies, and are thought by many astronomers to be material left over from the formation of the solar system that was not incorporated into any planetary bodies. Thus, comets may have clues about the early composition of the solar nebula.

The planets and asteroids orbit the Sun counterclockwise when viewed from above the Earth's North Pole, and most have roughly circular orbits that are confined to a relatively flat plane called the ecliptic plane. The spacing between the different orbits increases with increasing distance from the

Sun. The inner four planets (Mercury, Venus, Earth, and Mars), referred to as the terrestrial planets, have densities and properties that are roughly similar to Earth and are generally rocky in character. In contrast the outer planets (Jupiter, Saturn, Uranus, and Neptune), known as the Jovian planets, have much lower densities and are mostly gaseous or liquid in form. The Jovian planets are much more massive than the terrestrial planets, rotate more rapidly, have stronger magnetic fields than the terrestrial planets, and have systems of rings that circle the planets.

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