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| This period is part of the Paleozoic era. |
| Permian |
| Carboniferous |
| Devonian |
| Silurian |
| Ordovician |
| Cambrian |
The Silurian is a major division of the geologic timescale that extends from about 408.5 million years before the present (BP) with the end of the Ordovician period until 443.5 million years BP with the beginning of the Devonian period. As with most other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by 5-10 million years. The base of the Silurian is set at a major extinction event where 60% of marine species were wiped out.
The Silurian system was first described by Sir Roderick Murchison in the 1830s based on rocks in south Wales. It is named for a Welsh Celtic tribe -- the Silures. The series quickly came to overlap Adam Sedgwick's Cambrian sequence. Lapworth eventually resolved the conflict by defining a new Ordovician system including the contended beds.
The Silurian is usually broken into lower (Llandovery and Wenlock) and upper (Ludlow and Pridoli) subdivisions. Still, some schemes, use a lower (Llandovery), middle (Wenlock) and upper (Ludlow and Pridoli) breakdown. The series and stages from youngest to oldest are:
In North America the regional stages used are Cayugan (Late Silurian - Ludlow) Lockportian (Middle Silurian - Wenlock) Tonawandan (Middle Silurian - Wenlock) Ontarian (Lower Silurian - Llandovery) Alexandrian (Lower Silurian - Llandovery)
During the Silurian, GondwanaThis article is about the ancient supercontinent of Gondwana. For the region of India called Gondwana, see Gondwana (India). The southern supercontinent Gondwana (originally Gondwanaland included most of the landmasses which make up today's continents of remained in high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician. The melting of icecaps and glacierA glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. Equivalently, it is a multi-year ice accretion in mountainous terrain. The glacier fringe is the area where the glacier has recently melted. There ares contributed to a rise in sea level. The other continents drifted together near the equatorIn geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. The equator divides the surface into the Northern Hemisphere and the So, starting the formation of a second supercontinentA supercontinent is a mass of land comprising more than one continent. Since the definition of continent is arbitrary, the definition of supercontinent is also arbitrary (as is the definition of a subcontinent), but the term refers to a landmass containin known as LaurasiaLaurasia was a supercontinent that broke off from the Pangaean supercontinent in the late Mesozoic era. Laurasia divided into Eurasia and North America around 200 million years ago. The southern supercontinent created is called Gondwana. See also Alfred W.
During this period, the EarthEarth also known as the Earth or Terra is the planet on which we live, the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harbouring life. The pla entered a long warm greenhouseSaint Paul, Minnesota. A greenhouse (or glasshouse is a building where plants are cultivated. A greenhouse is built of glass or plastic; it heats up because the sun's incoming electromagnetic radiation (particularly infrared light) warms plants, soil, and phase, and warm shallow seas covered much of the equatorial land masses. The period witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of erratic climatic fluctuations.