Paleozoic era
Paleozoic era
| Noun | 1. |  Paleozoic era - from 544 million to about 230 million years ago |
| 单词 | paleozoic era | |||
| 释义 | Paleozoic eraPaleozoic era
Paleozoic eraSee also: Geologic Timescale (table)Geologic Timescale Paleozoic era(pā'lēəzō`ĭk), a major division (era) of geologic time (see Geologic TimescaleGeologic TimescaleEra Period Epoch Approximate duration (millions of years) Approximate number of years ago (millions of years) Cenozoic Quaternary Holocene 10,000 years ago to the present Pleistocene 2 . ..... Click the link for more information. , 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 PrecambrianPrecambrian, name of a major division of geologic time (see Geologic Timescale, table), from c.5 billion to 570 million years ago. It is now usually divided into the Archean and Proterozoic eons. Precambrian time includes 80% of the earth's history. ..... Click the link for more information. 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 periodOrdovician period [from the Ordovices, ancient tribe of N Wales], second period of the Paleozoic era of geologic time (see Geologic Timescale, table) from 505 to 438 million years ago. ..... Click the link for more information. , 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 periodCarboniferous period , fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. Historical Geology of the Period ..... Click the link for more information. . 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 SilurianSilurian period [from the Silures, ancient tribe of S Wales, where the period was first studied; named by the British geologist R. I. Murchison], third period of the Paleozoic era of geologic time (see Geologic Timescale, table) lasting from 405 to 435 million years ago. ..... Click the link for more information. 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. Paleozoic era
Synonyms for Paleozoic era
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