ERA - 8 reference results
era of good feelings, period in U.S. history (1817-23) when, the Federalist party having declined, there was little open party feeling. After the War of 1812 all sections were anxious to return to a normal life and to forget political issues. The phrase was coined at the time of President Monroe's good-will tour through the North, including New England, where a President had not been seen since the Virginia "dynasty" came into power. Under the surface, however, vast sectional issues were shaping themselves, and personal rivalries also were gathering strength to break loose in the campaign of 1824.
See G. Dangerfield, The Era of Good Feelings (1952, repr. 1963).
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era, period of historic time. In geology, it is the name applied to large divisions of geological process, e.g., Paleozoic era (see geology). In chronology an era is a period reckoned from a fixed point in time, as before or after the birth of Christ—before Christ, B.C.; Anno Domini [year of the Lord], A.D. The points best known for Western history are the creation of the world (Jewish, equivalent to 3761 B.C.; Byzantine, 5508 B.C.); the founding of the city of Rome [753 B.C.; year marked A.U.C. for ab urbe condita (from the founding of the city)]; the Hegira, the flight of Muhammad from Mecca (A.D. 622; abbreviation A.H.); and the founding of the Olympic games in ancient Greece (776 B.C.; time in Olympiads). Some people use C.E. (originally, Christian era, now common era) and B.C.E. (before common era) in place of A.D. and B.C., respectively. Since in different calendars years are of different lengths and do not begin on the same day (see calendar), several factors have to be used in changing the year of one era to that of another, and even with conversion charts there are still difficulties. Because of poor time calculation in earlier times, there may be anomalies in dating. Thus, the beginning of the Christian era, originally fixed probably by Dionysius Exiguus, was set a little too late. Therefore the actual birth of Jesus must be dated a little earlier, probably in 4 B.C. The term epoch is often confused with era in writing.
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Paleozoic era, a major division (era) of geologic time (see Geologic Timescale, table) occurring between 570 to 240 million years ago. It is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian (see each listed individually). During the hiatus between the late Precambrian and the Paleozoic era most of the evidence of the earth's early history was destroyed by erosion. From the beginning of the Paleozoic, shallow seas began to encroach on the continents. In North America, the era began with submerged geosynclines, or downward thrusts of the earth's crust, along the eastern, southeastern, and western sides of the continent, while the interior was dry land. As the era proceeded, the marginal seas periodically washed over the stable interior, leaving sedimentary deposits to mark their incursions. During the early part of the era, the area of exposed Precambrian, or shield, rocks in central Canada were eroding, supplying sediment to the geosynclines from the interior. Beginning in the Ordovician period, mountain building intermittently proceeded in the eastern part of the Appalachian geosyncline throughout the rest of the era, bringing in new sediments. Sediments washing from the Acadian Mts. filled the western part of the Appalachian geosyncline to form the famous coal swamps of the Carboniferous period. Uplift of the Appalachians caused the region to be never again inundated by vast marginal seas. Paleoclimatic studies and evidence of glaciers indicate that central Africa was most likely in the polar regions during the early Paleozoic. During the early Paleozoic, the huge continent Gondwanaland had either formed or was forming. By mid-Paleozoic, the collision of N America and Europe produced the Acadian-Caledonian uplifts, and a subduction plate uplifted eastern Australia. By late Paleozoic, continental collisions formed the supercontinent Pangaea and resulted in some of the great mountain chains, including the Appalachians, Urals, and Tasmans. The most noteworthy feature of Paleozoic life is the sudden appearance of nearly all of the invertebrate animal phyla in great abundance at the beginning of the Cambrian. A few primitive fishlike invertebrates, and then vertebrates, appeared in the Cambrian and Ordovician, scorpions in the Silurian period, land invertebrates and amphibians in the Devonian, land reptiles in the Carboniferous, and marine reptiles in the Permian. All reptiles increased in number and in variety by the late Permian. The plant life of the Paleozoic era reached its climax in the Carboniferous and was much contracted in the Permian.
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Mesozoic era [Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. Great crustal disturbances that marked the close of the Paleozoic and the beginning of the Mesozoic eras brought about drastic changes in the topography of North America. The Appalachian geosyncline, or downward thrust of the earth's crust, was replaced by the Appalachian Mts., and the eastern part of the continent was elevated during most of the era. The Appalachians were subjected to erosion, the products of which were deposited along the Atlantic coast, which had become a lowland region, or in the ocean beyond. Aside from the Appalachians, the other dry (consistently) areas of the continent were the Canadian Shield, the Antilles areas, and a mountain range elevated in part of the Cordilleran geosyncline. The Mesozoic tectonic activity included numerous subduction zones, such as those along the Pacific margin of the supercontinent Pangaea. Later, Pangaea began to split into the supercontinents of Gondwanaland and Laurasia, and N Africa began to rift apart. By the late Mesozoic, tectonic activity increased dramatically: the new Indian Ocean began to open, the Atlantic Ocean began to open along an extensive rift zone separating the Americas from Europe and Africa (see seafloor spreading). The life of the Mesozoic was dominated by the reptiles that evolved into the large land-dwelling dinosaurs of the Jurassic and Cretaceous periods. Flying reptiles and birds first appeared during the Mesozoic. Mammals probably evolved from some common ancestor of the reptiles early in the Triassic Period, but were subordinate to the reptiles until the end of the era, when the dominance of reptiles was ended by the extinction of the dinosaurs. Conifers dominated the plant life, with modern pines and sequoias first appearing. Flowering plants, deciduous trees, and grasses also appeared during this era.
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Cenozoic era, last major division of geologic time (see Geologic Timescale, table) lasting from 65 million years ago to the present. The Cenozoic is divided into the Tertiary (from 65 million years ago until 2 million years ago) and Quaternary (2 million years ago to the present) periods. Early in the Cenozoic, Greenland began to separate from Europe; Antarctica and Australia, and Africa and India also separated. The great Alpine-Himalayan mountain systems were formed; rifting with associated volcanic activity occurred in Africa, Europe, Asia, and Antarctica. In the late Cenozoic, the Cascade Range of volcanoes extended from southern British Columbia to N California, and represented a new volcanic arc superimposed on older structures. The volcanic arc is still periodically active today. Following the disturbances of the late Mesozoic era, the geography of North America had by the beginning of the Cenozoic attained substantially its present form. The only areas subjected to inundation by shallow marine waters were the Atlantic and Gulf coasts and a small area on the Pactific coast. Most of today's common plants and insects can be recognized in early Cenozoic fossils. Modern grasses appeared in the mid-Cenozoic. The animal life of the Cenozoic was dominated by mammals, which were most numerous in the Tertiary period and declined, with the exception of a few specialized types, in the Quaternary period. Theories explaining the decline or extinction of mammals during the Pliocene and Pleistocene epochs of the quaternary have ranged from a change in climate to the predation of humans. Cenozoic land mammals were never as large as the Mesozoic dinosaurs, but many were larger than today's mammals, and included beavers that grew to lengths of more than 7 ft (2 m), sloths as large as elephants, and birds up to 7 ft (2 m) in height. Around one million years ago, the ancestors of Homo sapiens, or modern humans, became dominant. Early humans are thought to have evolved in Africa during the Miocene and were widespread and accomplished toolmakers by the beginning of the Pleistocene; theory states that H. sapiens evolved in Asia and moved to Europe c.50,000 years ago, developed a form of agriculture in the Middle East c.10,000 years ago, and started writing and building the first cities c.4,000 years ago. See also geology.
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Very long span of geologic time; in formal usage, a portion of geologic time of the second-greatest magnitude (eons are longer). Three eras are recognized: Paleozoic, Mesozoic, and Cenozoic. Because of the difficulties involved in establishing accurate chronologies, the Precambrian, or earliest, eras are classified independently. An era is composed of one or more geologic periods.
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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Proposed but unratified amendment to the U.S. Constitution designed mainly to invalidate many state and federal laws that discriminated against women. Its central tenet was that sex should not be a determining factor in establishing the legal rights of individuals. It was first introduced in Congress in 1923, shortly after women obtained the right to vote. It was finally approved by the U.S. Senate 49 years later (1972) but was subsequently ratified by only 30 of the 50 state legislatures. Critics claimed it would cause women to lose privileges and protections, such as exemption from compulsory military service and economic support by their husbands. Supporters, led by the National Organization for Women, argued that discriminatory state and federal laws left many women in a state of economic dependency.
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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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