Earth Summit officially United Nations Conference on Envi¬ ronment and Development Conference held in Rio de Janeiro (June 3-14, 1992) to reconcile worldwide economic development with environmental protection. It was the largest gathering of world leaders in history, with 117 heads of state and representatives of 178 countries. Biodiversity, global warming, sustainable development, and preservation of tropical rain forests were among the topics discussed. Five international agreements were signed amid tensions between the industrialized coun¬ tries of the North and the poorer developing states of the South, who were reluctant to accept environmental restrictions without increased Northern economic aid. Follow-up meetings were held in 1997 at the UN General Assembly in New York and in 2002 in Johannesburg, S.Af. See also Rio Treaty.
earthenware Pottery that has been fired at low heat and is slightly more porous and coarser than stone¬ ware and porcelain. For practical and decorative purposes, it is usually glazed. The earliest known pottery, a soft earthenware excavated at a Neolithic settlement in Turkey, is thought to be about 9,000 years old.
Earthenware is still widely used for cooking, freezing, and serving. See also CREAMWARE.
earthquake Sudden shaking of the ground caused by a disturbance deeper within the crust of the Earth.
Most earthquakes occur when masses of rock straining against one another along fault lines suddenly fracture and slip. The Earth’s major earthquakes occur mainly in belts coinciding with the margins of tec¬ tonic plates. These include the Circum-Pacific Belt, which affects New Zealand, New Guinea, Japan, the Aleutian Islands, Alaska, and the western coasts of North and South America; the Alpide Belt, which passes through the Mediterranean region eastward through Asia; oceanic ridges in the Arctic, Atlantic, and western Indian oceans; and the rift valleys of East Africa. The “size,” or magnitude, of earthquakes is usually expressed in terms of the Richter scale, which assigns levels from 1.0 or lower to 8.0 or higher. The largest quake ever recorded (Richter magnitude 9.5) occurred off the coast of Chile in 1960. The “strength” of an earthquake is rated in intensity scales such as the Mercalli scale, which assigns quali¬ tative measures of damage to terrain and structures that range from “not
felt” to “damage nearly total.” The most destructive quake of modem times occurred in 1976, when the city of Tangshan, China, was leveled and more than 250,000 people killed. See also seismic wave; seismology.
earthquake-resistant structure Building designed to prevent total collapse, preserve life, and minimize damage in case of an earthquake or tremor. Earthquakes exert lateral as well as vertical forces, and a struc¬ ture’s response to their random, often sudden motions is a complex task that is just beginning to be understood. Earthquake-resistant structures absorb and dissipate seismically induced motion through a combination of means: damping decreases the amplitude of oscillations of a vibrating structure, while ductile materials (e.g., steel) can withstand considerable inelastic deformation. If a skyscraper has too flexible a structure, then tre¬ mendous swaying in its upper floors can develop during an earthquake. Care must be taken to provide built-in tolerance for some structural dam¬ age, resist lateral loading through stiffeners (diagonal sway bracing), and allow areas of the building to move somewhat independently.
earthshine Sunlight reflected from Earth, especially that reflected onto the dark side of the Moon. For a few days before and after each new moon, this doubly reflected light is powerful enough to make the whole Moon vis¬ ible, producing the effect, in the case of the new moon, of “the new moon holding the old moon in her arms.”
earthworm Any of more than 1,800 species of terrestrial worms, particularly members of the genus Lumbricus (class Oligochaeta of the annelid order). Earthworms exist in all soils of the world that have suf¬ ficient moisture and organic content.
The most common U.S. species, L. terrestris, grows to about 10 in. (25 cm), but an Australian species can grow as long as 11 ft (3.3 m). The segmented body is tapered at both ends. Earthworms eat decaying organisms and, in the process, ingest soil, sand, and pebbles, which aer¬ ates the soil, promotes drainage, and improves the soil’s nutrient content for plants. Earthworms are eaten by many animals.
earwig Any of about 1,100 insect species (order Dermaptera) charac¬ terized by large membranous hind wings that lie hidden under short, leathery forewings. Species vary from 0.2 to 2 in. (5 to 50 mm) long, and all are flat, slender, and dark, with a shiny outer covering and simple biting mouthparts. Several spe¬ cies can shoot a foul-smelling liquid, formed in abdominal glands, as far as 4 in. (10 cm). Earwigs have a pair of forceps-like tail pincers (cerci) at the back end of the abdomen that may function in defense, capturing prey, folding wings, or fighting courtship battles.
easement In Anglo-American property law, an interest in land owned by another that entitles its holder to a specific limited use or enjoyment, such as the right to cross the land or have a view over it continue unob¬ structed. It may be created expressly by a written deed of grant convey¬ ing the specific usage right, or it may be created by implication, as when an owner divides property into two parcels in such a way that an already existing, obvious, and continuous use of one parcel (e.g., for access) is necessary for the reasonable enjoyment of the other. Some U.S. states permit the creation of an easement by prescription (acquisition of an interest), as when one person makes continuous use of another’s land for some specified period of time (e.g., 20 years). Utility companies often own easements in gross; these are not dependent on ownership of the sur¬ rounding estate. Numerous other kinds of easements have been important in Anglo-American law. See also real and personal property.
East, Edward Murray (b. Oct. 4, 1879, Du Quoin, Ill., U.S.—d. Nov. 9, 1938, Boston, Mass.) U.S. plant geneticist, agronomist, and chemist.
Lead-glazed earthenware water pot, Paris, 15th century, in the National Museum of Ceramics, Sevres, France.
COURTESY OF THE MUSEE NATIONAL DE LA CERAMIQUE, SEVRES
Earthshine on the moon.
COURTESY OF YERKES OBSERVATORY, WISCONSIN
Earthworm (Lumbricus terrestris).
JOHN MARKHAM
© 2006 Encyclopaedia Britannica, Inc.
East African Rift ► East Sussex I 589
He finished high school at age 15 and received an M.S. in 1904. He was particularly interested in determining and controlling the protein and fat content of corn, both of which significantly influence its value as animal feed. His research, with that of George Harrison Shull, led to the devel¬ opment of modem-day hybrid corn. Commercial production of hybrid seed corn was made possible by the work of his student Donald F. Jones (1890-1963). East’s work helped make possible studies in the field of population genetics.
East African Rift System See Great Rift Valley
East Anglia Traditional region of England. It consists of the historic counties of Norfolk and Suffolk and parts of Cambridgeshire and Essex, and its traditional centre is the city of Norwich. The easternmost area in England, it has been settled for thousands of years. Colchester, the oldest recorded town in England, was important in pre-Roman and Roman times. East Anglia was one of the kingdoms of Anglo-Saxon England, and it was ruled by Danes in the 9th century. During the medieval period it was known for its woolen products, but the region’s modern economy is pre¬ dominantly agricultural. Along the coast are many important fishing ports and holiday resorts.