The Ordovician period, an important period of the Earth's Paleozoic Era, began around 48.5 billion years ago, ending at 44.3 billion years ago. The name is derived from the Ordovices, an ancient ethnic group in England. At the beginning of the 9th century, the English geologist Ri.m.Cornwall, Ri.m.While studying the geology of northern Wales, Conway discovered a set of fossil-rich strata that he considered distinct from the Silurian strata, hence the name Ordovician. The name was later widely accepted by the international geological community.
The geological characteristics of the Ordovician are mainly manifested in crustal movements, tectonic changes and sedimentary environments. In terms of crustal movements, the Earth's plate movements were relatively active during the Ordovician period, especially in the tectonic belts between land and sea, such as the Paleo-Tethys Ocean between the Paleo-Arctic and Paleo-Southern Continents. In terms of tectonic changes, large-scale tectonic movements, such as the Caledonian movement, occurred in the late Ordovician, which led to the closure of the Paleo-Tethys Ocean and the convergence of land. In terms of sedimentary environment, the Ordovician strata are mainly distributed in shallow sea and terrestrial environments, of which the sediments of the shallow marine environment are dominated by limestone and shale, and the sediments of the terrestrial environment are mainly sandstone and mudstone.
The Ordovician period was an important period in the history of the evolution of life on Earth, and many major geohistorical events occurred. First of all, in the early Ordovician period, the earth experienced an ice age, and glacial activity led to the cooling of the global climate, which had a great impact on the living environment of living things. Second, during the late Ordovician period, the Earth experienced a large-scale extinction event known as the Ordovician-Silurian extinction event, which was the second large-scale extinction event in the history of the Earth. This extinction event led to the disappearance of many marine organisms, creating space for subsequent organisms to evolve.
The Ordovician is not only known for its geological features, but also for its rich animal fossil record. A large number of complex and diverse fossils of marine life have been found in the strata of this period, revealing the prosperity and diversity of the Ordovician biosphere.
The Ordovician extinction event was one of five mass extinction events in Earth's history, occurring about 4400 million years ago. This extinction event had a huge impact on marine life at that time, resulting in the extinction of about 85% of marine life species, so it is considered the first mass extinction event since the Phanerozoic.
There are various hypotheses about the cause of this extinction event. Among them, climate change and sea level rise and fall are considered to be the main influencing factors. According to research, during the late Ordovician period, the Earth experienced a sharp cooling event that caused glaciers to expand and sea levels to drop significantly. This drastic climate change has had a great impact on the living environment of marine organisms, and many organisms have become extinct because they are unable to adapt to the new environment.
In addition, there are hypotheses that this extinction event may be related to gamma-ray bursts produced by supernova explosions. It is speculated that gamma rays emitted by a very supernova at the time may have damaged the Earth's ozone layer, causing ultraviolet rays to hit the surface in large quantities and causing fatal damage to marine life. At the same time, gamma rays may also disrupt air molecules and form toxic gases, further exacerbating the extinction of organisms.