Petrified Forest National Park National park, eastern Arizona, U.S. Established as a national monument in 1906 and as a national park in 1962, it has an area of 146 sq mi (378 sq km). It features extensive exhibits of petrified wood in several “forest” areas, fossilized leaves, plants, and broken logs, and the Painted Desert. Other features include petroglyphs and ancient Pueblo Indian ruins.
petrified wood Fossil formed by the infiltration of minerals into cavi¬ ties between and within cells of natural wood, usually by silica (silicon dioxide, Si0 2 ) or calcite (calcium carbonate, CaC0 3 ). Often this replace¬ ment of organic tissue by mineral deposits is so precise that the internal structure as well as the external shape is faithfully represented; sometimes even the cell structure may be determined.
Petrobras \'pe-tro-,bras\ officially Petroleo Brasileiro SA Brazil¬ ian oil and natural-gas company, the largest corporation in South America. It was founded in 1953 as a government-owned monopoly to prospect, extract, and refine domestic petroleum and to transport that oil and its derivatives. A government agency sets its policies and oversees its devel¬ opment. Although mainly devoted to developing petroleum sources in Brazil, Petrobras also has interests in the Middle East, North Africa, and Colombia. In 1995, as part of a campaign to privatize state-owned indus¬ tries, the Brazilian government ended the company’s monopoly and allowed foreign competition. Petrobras subsequently developed joint ven¬ tures with foreign businesses.
petrochemical Strictly, any of a large class of chemicals (as distinct from fuels) derived from petroleum and natural gas. The category has been broadened to include a much larger range of organic compounds and a few inorganic compounds (including carbon black, sulfur, and ammonia). Some materials cannot be classifed unequivocally because they have alter¬ native sources (benzene from coal, ethanol from fermentation). Like crude oil and natural gas, most petrochemicals consist mainly of carbon and hydrogen and are called hydrocarbons. Petrochemicals used as raw mate¬ rials (feedstocks) include ethylene, propylene, butadiene, benzene, toluene, xylene, and naphthalene. Among the myriad petrochemical products are plastics (e.g., polyethylene, polypropylene, polystyrene), soaps and deter¬ gents, solvents, drugs, fertilizers, pesticides, explosives, synthetic fibres and rubberss, paints, epoxies, flooring and insulating materials, luggage, and recording disks and tapes.
Petrodvorets \,pyi-tr3-dva-'ryets\ formerly (until 1944) Peterhof City (pop., 1995 est.: 82,000), northwestern Russia. Located near St. Petersburg, it was founded by Peter I the Great as a country estate in 1709. After visiting France in 1717, he decided to create a residence that would rival the Palace of Versailles. The Baroque Grand Palace (1714-28) was designed by Domenico Trezzini, and its gardens by Alexandre Le Blond (1679-1719). It became the most lavish and popular of the Russian royal summer residences. Today the Grand Palace (now a museum) and the vast park, with 39 mi (63 km) of canals that connect the intricate system of fountains, are part of the 2,500-acre (1,000-hectare) preserved area in the city of Petrodvorets.
Petrograd See Saint Petersburg
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petrol ► peyote I 1483
petrol See gasoline
Petroleos de Venezuela ^pe-tro-'la-os-tha-.ve-nsz-'wa-lsV, SA (PDVSA) State-owned Venezuelan energy company with interests in oil, natural gas, coal, and petrochemicals. It was created in 1976 through the nationalization of Venezuela’s petroleum industry, which had been con¬ trolled by foreign companies since the end of World War I. Petroleos de Venezuela engages in the exploration, refining, and marketing of oil, pet¬ rochemicals, and natural gas in many parts of the world. Through its acquisition of CITGO Petroleum in 1990, PDVSA became a leading sup¬ plier of gasoline and other petroleum products in the U.S. Given the scale of its operations, PDVSA usually earns the largest share of Venezuela’s foreign currency.
petroleum or crude oil Complex mixture of hydrocarbons derived from the geologic transformation and decomposition of plants and ani¬ mals that lived hundreds of millions of years ago. As a technical term, petroleum encompasses the liquid (crude oil), gaseous (natural gas), and viscous or solid (bitumen, asphalt) forms of hydrocarbons that occur in the Earth, but the meaning is often restricted to the liquid oil form. Crude oil and natural gas are the most important primary fossil fuels. Asphalt has been used since ancient times to caulk ships and pave roads. In the mid 1800s petroleum began to replace whale oil in lamps, and the first well specifically to extract it was drilled in 1859. The development of the auto¬ mobile gave petroleum a new role as the source of gasoline. Petroleum and its products have since been used as fuels for heating, for land, air, and sea transport, and for electric power generation and as petrochemical sources and lubricants. Crude oil and natural gas, produced mostly in Saudi Arabia, the U.S., and Russia, now account for about 60% of world energy consumption; the U.S. is by far the largest consumer. At present rates of consumption, the known supply will be exhausted by the mid 21st century. Petroleum is recovered from drilled wells, transported by pipe¬ line or tanker ship to refineries, and there converted to fuels and petro¬ chemicals.
petroleum trap Subsurface reservoir of petroleum. The oil is always accompanied by water and often by natural gas; all are confined in porous rock. The natural gas, being lightest, occupies the top of the trap and is underlain by the oil and then the water. A layer of impervious rock, called the roof rock, prevents the escape of the petroleum. The part of the trap that is actually occupied by the oil and gas is called the petroleum res¬ ervoir.
petrology Scientific study of rocks, including their composition, tex¬ ture, and structure; occurrence and distribution; and conditions of origin. Petrology is concerned with all three major types of rocks: igneous, meta- morphic, and sedimentary. The subdiscipline of experimental petrology involves synthesizing rocks in the laboratory to ascertain the physical and chemical conditions under which they form. The subdiscipline of petrog¬ raphy is concerned primarily with the systematic study and description of rocks using a petrographic microscope.
Petronas \pe-'tro-nos\ Towers Twin stainless-steel-clad skyscrapers, linked by a skybridge, in Kuala Lumpur, Malaysia. Designed by Cesar Pelli (b. 1926) and completed in 1998, the circular, step-tapered towers house the headquarters of Malaysia’s national petroleum company. Each tower is 88 stories high, has a structural frame of high-strength, steel- reinforced concrete, and reaches a height of 1,483 ft (451.9 m)—a figure that includes a pinnacle and steel spire atop each. In 1996, after achiev¬ ing their full height, the towers were considered the world’s tallest build¬ ings, surpassing the then-tallest Sears Tower; they, in turn, were superseded in 2003 by the Taipei 101 (Taipei Financial Center) building in Taipei, Taiwan, that rose to 1,667 ft (508 m).
Petronius Arbiter, Gaius orig. Titus Petronius Niger (d. ad 66)
Roman writer. Of a noble family, Petronius belonged to a class of idle pleasure-seekers, but he served ably as governor of the Asian province of Bithynia and as consul in Rome. After being appointed Nero’s authority on taste (hence “Arbiter”), he was accused of plotting to kill the emperor and, though innocent, committed suicide. He is the reputed author of the Satyricon, a comic picaresque novel vividly portraying contemporary Roman society through the escapades of a disreputable trio of adventur¬ ers, with unrelated stories and the author’s commentaries on Roman life interspersed.