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It occurs when the rate of extinction increases with respect to the background extinction rate [1] and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty.
A growing number of scientists believe a sixth mass extinction event of a magnitude equal to the prior five has been unfolding for the past 10,000 years as humans have made their mark around the ...
Extinction may occur a long time after the events that set it in motion, a phenomenon known as extinction debt. Assessing the relative importance of genetic factors compared to environmental ones as the causes of extinction has been compared to the debate on nature and nurture. [37]
Permian–Triassic extinction event 252 Ma Large igneous province (LIP) eruptions [ 23 ] from the Siberian Traps , [ 24 ] an impact event (the Wilkes Land Crater ), [ 25 ] an Anoxic event , [ 26 ] an Ice age , [ 27 ] or other possible causes
Mass extinctions are characterized by the loss of at least 75% of species within a geologically short period of time (i.e., less than 2 million years). [18] [51] The Holocene extinction is also known as the "sixth extinction", as it is possibly the sixth mass extinction event, after the Ordovician–Silurian extinction events, the Late Devonian extinction, the Permian–Triassic extinction ...
The second mass extinction was the Late Devonian extinction, probably caused by the evolution of trees, which could have led to the depletion of greenhouse gases (like CO 2) or the eutrophication of water. 70% of all species became extinct. [179] The third mass extinction was the Permian-Triassic, or the Great Dying, event.
From around 1850 to 1980, most geologists endorsed uniformitarianism ("The present is the key to the past") and gradualism (geologic change occurs slowly over long periods of time) and rejected the idea that cataclysmic events such as earthquakes, volcanic eruptions, or floods of vastly greater power than those observed at the present time ...
The Cretaceous–Paleogene (K–Pg) extinction event, [a] also known as the K–T extinction, [b] was the mass extinction of three-quarters of the plant and animal species on Earth [2] [3] approximately 66 million years ago. The event caused the extinction of all known non-avian dinosaurs.