late devonian extinction is the name of the first extinction.
late devonian extinction is the name of the first extinction.
what is the name of the first extinction?
late devonian extinction
the great oxygenation event, which occurred around 2.45 billion years ago, was probably the first major extinction event. since the cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate. the most recent and arguably best-known, the cretaceous–paleogene extinction event, which occurred approximately million years ago (ma), was a large-scale mass extinction of animal and plant species in a geologically short period of time. in addition to the five major mass extinctions, there are numerous minor ones as well, and the ongoing mass extinction caused by human activity is sometimes called the sixth extinction. mass extinctions seem to be a mainly phanerozoic phenomenon, with extinction rates low before large complex organisms arose.
extinction event
the late ordovician glaciation coincided with the second largest of the 5 major extinction events, known as the ordovician–silurian extinction event. this period is the only known glaciation to occur alongside of a mass extinction event. the extinction event consisted of two discrete pulses. the first pulse of extinctions is thought to have taken place because of the rapid cooling, and increased oxygenation of the water column. this first pulse was the larger of the two and caused the extinction of most of the marine animal species that existed in the shallow and deep oceans. the second phase of extinction was associated with strong sea level rise, and due to the atmospheric conditions, namely oxygen levels being at or below 50% of present-day levels, high levels of anoxic waters would have been common. this anoxia would have killed off many of the survivors of the first extinction pulse. in all the extinction event of the late ordovician saw a loss of 85% of marine animal species and 26% of animal families.
late ordovician glaciation