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An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the
biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near ...

biodiversity
on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
. Such an event is identified by a sharp change in the diversity and abundance of
multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biol ...
s. It occurs when the rate of
extinction Extinction is the termination of a kind of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by ...

extinction
increases with respect to the rate of
speciation Speciation is the evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes that are ...

speciation
. The number of major mass extinctions in the last 440 million years are estimated from as few as five to more than twenty. These differences stem from disagreement as to what constitutes an extinction event as "major", and the data chosen to measure past diversity. Because most diversity and
biomass Biomass is plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position ...
on Earth is
microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the
biosphere The biosphere (from βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all s. It can also be termed the zo ...
rather than the total diversity and abundance of life.
Extinction Extinction is the termination of a kind of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by ...

Extinction
occurs at an uneven rate. Based on the
fossil record A fossil (from Classical Latin: , literally 'obtained by digging') is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, Seashell, shells, exoskeletons, stone imprints of a ...
, the background rate of extinctions on Earth is about two to five
taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of families is to maintain the w ...
of
marine animal Marine life, sea life, or ocean life is the plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, thr ...

marine animal
s every million years. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to
land animal Terrestrial animals are animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellula ...
s. The
Great Oxidation Event The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen catastrophe, and the Oxygen Crisis, was a time interval when the Earth's atmosphere File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere ...
, 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 The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden of three-quarters of the and on , approximately 66 million years ago. With the exception of some species such as ...
, which occurred approximately Ma (million years ago), 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 The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (geology), epoch (with the more recent time sometimes called Anthro ...
. Mass extinctions seem to be a mainly
Phanerozoic The Phanerozoic Eon is the current in the , and the one during which abundant and has existed. It covers million years to the present, and it began with the Period when animals first developed hard shells preserved in the fossil record. The ...
phenomenon, with extinction rates being low before large complex organisms arose.


Major extinction events

In a landmark paper published in 1982,
Jack SepkoskiJoseph John Sepkoski Jr. (July 26, 1948 – May 1, 1999) was a University of Chicago The University of Chicago (UChicago, U of C, or Chicago) is a private research university in Chicago (''City in a Garden''); I Will , image_map ...
and David M. Raup identified five mass extinctions. They were originally identified as outliers to a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applied to the accumulating data, it has been established that multicellular animal life has experienced five major and many minor mass extinctions. The "Big Five" cannot be so clearly defined, but rather appear to represent the largest (or some of the largest) of a relatively smooth continuum of extinction events. #
Ordovician–Silurian extinction events The Ordovician–Silurian extinction events, also known as the Late Ordovician mass extinction, are collectively the second-largest of the five major extinction events in Earth's history in terms of percentage of Genus, genera that became extinct. ...
(End Ordovician or O–S): 450–440 Ma at the
Ordovician The Ordovician ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions i ...

Ordovician
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician The Ordovician ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-refere ...
transition. Two events occurred that killed off 27% of all families, 57% of all genera and 85% of all species. Together they are ranked by many scientists as the second-largest of the five major extinctions in Earth's history in terms of percentage of
genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
that became extinct. In May 2020, studies suggested the cause of the mass extinction was due to
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been , but the current changes are more rapid than any known events in Earth's history. The main cau ...

global warming
, related to
volcanism Volcanism (or volcanicity) is the phenomenon of eruption of molten rock (magma) onto the Earth#Surface, surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called ...
, and anoxia, and not due, as considered earlier, to cooling and
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...
. #
Late Devonian extinction The Late Devonian extinction was one of five major extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a shar ...
: 375–360 Ma near the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
Carboniferous The Carboniferous ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other ...
transition. At the end of the Frasnian Age in the later part(s) of the
Devonian Period The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
, a prolonged series of extinctions eliminated about 19% of all families, 50% of all
genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
and at least 70% of all species. This extinction event lasted perhaps as long as 20 million years, and there is evidence for a series of extinction pulses within this period. #
Permian–Triassic extinction event The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian The Permian ( ) is a geologic period ...
(End Permian): 252 Ma at the
Permian The Permian ( ) is a and which spans 47 million years from the end of the Period million years ago (Mya), to the beginning of the Period 251.902 Mya. It is the last period of the Era; the following Triassic Period belongs to the Era. The c ...
Triassic The Triassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...

Triassic
transition. Earth's largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species (53% of marine families, 84% of marine genera, about 81% of all marine species and an estimated 70% of land species, including
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
s). The highly successful marine arthropod, the
trilobite Trilobites (; meaning "three lobes") are a group of marine s that form the Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the of the ( ...

trilobite
, became extinct. The evidence regarding
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s is less clear, but new taxa became dominant after the extinction. The "Great Dying" had enormous evolutionary significance: on land, it ended the primacy of . The recovery of vertebrates took 30 million years, but the vacant created the opportunity for
archosaur Archosauria ("ruling reptiles") is a clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. ...
s to become ascendant. In the seas, the percentage of animals that were sessile dropped from 67% to 50%. The whole late Permian was a difficult time for at least marine life, even before the "Great Dying". #
Triassic–Jurassic extinction event The Triassic–Jurassic (Tr-J) extinction event, sometimes called the end-Triassic extinction, marks the boundary between the Triassic The Triassic ( ) is a geologic period A geological period is one of the several subdivisions of geologic time ...
(End Triassic): 201.3 Ma at the
Triassic The Triassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...

Triassic
Jurassic The Jurassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
transition. About 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species became extinct. Most non-dinosaurian
archosaur Archosauria ("ruling reptiles") is a clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. ...
s, most
therapsid Therapsida is a major group of eupelycosauria Eupelycosauria is a large clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic— ...

therapsid
s, and most of the large
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s were eliminated, leaving
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s with little terrestrial competition. Non-dinosaurian archosaurs continued to dominate aquatic environments, while continued to dominate marine environments. The
Temnospondyl Temnospondyli (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...
lineage of large amphibians also survived until the Cretaceous in Australia (e.g., ''
Koolasuchus ''Koolasuchus'' is an extinct genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may als ...

Koolasuchus
''). #
Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden of three-quarters of the and on , approximately 66 million years ago. With the exception of some species such as ...
(End Cretaceous, K–Pg extinction, or formerly K–T extinction): Ma at the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of division ...

Cretaceous
(
Maastrichtian The Maastrichtian () is, in the ICS ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to contr ...
) –
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous The Cretaceous ( ) is a geological period A geologi ...
(
Danian The Danian is the oldest age or lowest stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The S ...
) transition interval. The event formerly called the Cretaceous-Tertiary or K–T extinction or K–T boundary is now officially named the Cretaceous–Paleogene (or K–Pg) extinction event. About 17% of all families, 50% of all
genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
and 75% of all species became extinct. In the seas all the
ammonites Ammonoids are a group of extinct Extinction is the termination of a kind of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Li ...

ammonites
,
plesiosaurs The Plesiosauria (; Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...

plesiosaurs
and
mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Ma ...
s disappeared and the percentage of sessile animals (those unable to move about) was reduced to about 33%. All non-avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s became extinct during that time. The boundary event was severe with a significant amount of variability in the rate of extinction between and among different
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
s.
Mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s and
bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

bird
s, the former descended from the synapsids and the latter from
theropod Theropoda ( from Ancient Greek, Greek 'wild beast' and 'foot'), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three-toed limbs. Theropods are generally classed as a group of saurischian d ...
dinosaurs, emerged as dominant terrestrial animals. Despite the popularization of these five events, there is no definite line separating them from other extinction events; using different methods of calculating an extinction's impact can lead to other events featuring in the top five. Older fossil records are more difficult to interpret. This is because: * Older fossils are harder to find as they are usually buried at a considerable depth. * Dating of older fossils is more difficult. * Productive fossil beds are researched more than unproductive ones, therefore leaving certain periods unresearched. * Prehistoric environmental events can disturb the
deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
process. * The preservation of fossils varies on land, but marine fossils tend to be better preserved than their sought after land-based counterparts. It has been suggested that the apparent variations in marine biodiversity may actually be an artifact, with abundance estimates directly related to quantity of rock available for sampling from different time periods. However, statistical analysis shows that this can only account for 50% of the observed pattern, and other evidence such as fungal spikes (geologically rapid increase in
fungal A fungus (plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity great ...

fungal
abundance) provides reassurance that most widely accepted extinction events are real. A quantification of the rock exposure of Western Europe indicates that many of the minor events for which a biological explanation has been sought are most readily explained by
sampling bias In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with ...
. Research completed after the seminal 1982 paper (Sepkoski and Raup) has concluded that a sixth mass extinction event is ongoing: :6.
Holocene extinction The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (geology), epoch (with the more recent time sometimes called Anthr ...
: Currently ongoing. Extinctions have occurred at over 1000 times the
background extinction rateBackground extinction rate, also known as the normal extinction rate, refers to the standard rate of extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is gen ...
since 1900. The mass extinction is a result of
human activity Human behavior is the potential and expressed capacity ( mentally, physically, and socially) of human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairl ...
, driven by
population growth Population growth is the increase in the number of people in a population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size ...
and
overconsumption Overconsumption describes a situation where the use of a natural resource has exceeded the Sustainable yield, sustainable capacity of a system. A prolonged pattern of overconsumption leads to the eventual loss of resource bases. The term overconsu ...
of the earth's natural resources. The 2019 global biodiversity assessment by
IPBES The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) is an intergovernmental organization established to improve the interface between science and policy on issues of biodiversity Biodiversity is the bi ...
asserts that out of an estimated 8 million species, 1 million plant and animal species are currently threatened with extinction. In late 2021, WWF Germany suggested that over a million species could go extinct within a decade in the "largest mass extinction event since the end of the dinosaur age." More recent research has indicated that the
End-Capitanian extinction event The Capitanian extinction event was an extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in th ...
likely constitutes a separate extinction event from the Permian–Triassic extinction event; if so, it would be larger than many of the "Big Five" extinction events.


List of extinction events


Evolutionary importance

Mass extinctions have sometimes accelerated the
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
of . When dominance of particular ecological niches passes from one group of organisms to another, it is rarely because the newly dominant group is "superior" to the old but usually because an extinction event eliminates the old, dominant group and makes way for the new one, a process known as
adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic inte ...
. For example, mammaliformes ("almost mammals") and then
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s existed throughout the reign of the
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s, but could not compete in the large terrestrial vertebrate niches which dinosaurs monopolized. The end-Cretaceous mass extinction removed the non-avian dinosaurs and made it possible for mammals to expand into the large terrestrial vertebrate niches. The dinosaurs themselves had been beneficiaries of a previous mass extinction, the end-Triassic, which eliminated most of their chief rivals, the crurotarsans. Another point of view put forward in the Escalation hypothesis predicts that species in ecological niches with more organism-to-organism conflict will be less likely to survive extinctions. This is because the very traits that keep a species numerous and viable under fairly static conditions become a burden once population levels fall among competing organisms during the dynamics of an extinction event. Furthermore, many groups which survive mass extinctions do not recover in numbers or diversity, and many of these go into long-term decline, and these are often referred to as " Dead Clades Walking". However, clades that survive for a considerable period of time after a mass extinction, and which were reduced to only a few species, are likely to have experienced a rebound effect called the "
push of the pastThe push of the past is a type of survivorship bias Survivorship bias or survival bias is the logical error of concentrating on the people or things that made it past some selection process and overlooking those that did not, typically because of th ...

push of the past
". Darwin was firmly of the opinion that biotic interactions, such as competition for food and space—the ‘struggle for existence’—were of considerably greater importance in promoting evolution and extinction than changes in the physical environment. He expressed this in ''The Origin of Species'': "Species are produced and exterminated by slowly acting causes…and the most import of all causes of organic change is one which is almost independent of altered…physical conditions, namely the mutual relation of organism to organism-the improvement of one organism entailing the improvement or extermination of others".


Patterns in frequency

It has been suggested variously that extinction events occurred periodically, every 26 to 30 million years, or that diversity fluctuates episodically every ~62 million years.Different cycle lengths have been proposed; e.g. by Various ideas attempt to explain the supposed pattern, including the presence of a hypothetical companion star to the sun, oscillations in the galactic plane, or passage through the Milky Way's spiral arms. However, other authors have concluded that the data on marine mass extinctions do not fit with the idea that mass extinctions are periodic, or that ecosystems gradually build up to a point at which a mass extinction is inevitable. Many of the proposed correlations have been argued to be spurious. Others have argued that there is strong evidence supporting periodicity in a variety of records, and additional evidence in the form of coincident periodic variation in nonbiological geochemical variables. Mass extinctions are thought to result when a long-term stress is compounded by a short-term shock. Over the course of the
Phanerozoic The Phanerozoic Eon is the current in the , and the one during which abundant and has existed. It covers million years to the present, and it began with the Period when animals first developed hard shells preserved in the fossil record. The ...
, individual taxa appear to have become less likely to suffer extinction, which may reflect more robust food webs, as well as fewer extinction-prone species, and other factors such as continental distribution. However, even after accounting for sampling bias, there does appear to be a gradual decrease in extinction and origination rates during the Phanerozoic. This may represent the fact that groups with higher turnover rates are more likely to become extinct by chance; or it may be an artefact of taxonomy: families tend to become more speciose, therefore less prone to extinction, over time; and larger taxonomic groups (by definition) appear earlier in geological time. It has also been suggested that the oceans have gradually become more hospitable to life over the last 500 million years, and thus less vulnerable to mass extinctions,
Dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In c ...
became more widespread and penetrated to greater depths; the development of life on land reduced the run-off of nutrients and hence the risk of
eutrophication Eutrophication (from Greek ''eutrophos'', "well-nourished") is the process by which an entire body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokm ...

eutrophication
and
anoxic event 200px, This world perspective of oceanic currents demonstrates the interdependencies of transnational regions on circulating currents. Oceanic anoxic events or anoxic events ( anoxia conditions) describe periods wherein large expanses of Earth's ...
s; and marine ecosystems became more diversified so that
food chain A food chain is a linear network of links in a food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is Consumer-resource sy ...

food chain
s were less likely to be disrupted.
but susceptibility to extinction at a taxonomic level does not appear to make mass extinctions more or less probable.


Causes

There is still debate about the causes of all mass extinctions. In general, large extinctions may result when a biosphere under long-term stress undergoes a short-term shock. An underlying mechanism appears to be present in the correlation of extinction and origination rates to diversity. High diversity leads to a persistent increase in extinction rate; low diversity to a persistent increase in origination rate. These presumably ecologically controlled relationships likely amplify smaller perturbations (asteroid impacts, etc.) to produce the global effects observed.


Identifying causes of specific mass extinctions

A good theory for a particular mass extinction should: (i) explain all of the losses, not just focus on a few groups (such as dinosaurs); (ii) explain why particular groups of organisms died out and why others survived; (iii) provide mechanisms which are strong enough to cause a mass extinction but not a total extinction; (iv) be based on events or processes that can be shown to have happened, not just inferred from the extinction. It may be necessary to consider combinations of causes. For example, the marine aspect of the end-Cretaceous extinction appears to have been caused by several processes which partially overlapped in time and may have had different levels of significance in different parts of the world. Arens and West (2006) proposed a "press / pulse" model in which mass extinctions generally require two types of cause: long-term pressure on the eco-system ("press") and a sudden catastrophe ("pulse") towards the end of the period of pressure. Their statistical analysis of marine extinction rates throughout the
Phanerozoic The Phanerozoic Eon is the current in the , and the one during which abundant and has existed. It covers million years to the present, and it began with the Period when animals first developed hard shells preserved in the fossil record. The ...
suggested that neither long-term pressure alone nor a catastrophe alone was sufficient to cause a significant increase in the extinction rate.


Most widely supported explanations

Macleod (2001) summarized the relationship between mass extinctions and events which are most often cited as causes of mass extinctions, using data from Courtillot ''et al.'' (1996), Hallam (1992) and Grieve ''et al.'' (1996): *
Flood basalt A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot (geology), hotspot reaching ...
events: 11 occurrences, all associated with significant extinctionsThe earliest known flood basalt event is the one which produced the
Siberian Traps The Siberian Traps (russian: Сибирские траппы, ) is a large region of volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other ...
and is associated with the end-Permian extinction.
Some of the extinctions associated with flood basalts and sea-level falls were significantly smaller than the "major" extinctions, but still much greater than the background extinction level. But Wignall (2001) concluded that only five of the major extinctions coincided with flood basalt eruptions and that the main phase of extinctions started before the eruptions. * Sea-level falls: 12, of which seven were associated with significant extinctions. * : one large impact is associated with a mass extinction, that is, the Cretaceous–Paleogene extinction event; there have been many smaller impacts but they are not associated with significant extinctions. The most commonly suggested causes of mass extinctions are listed below.


Flood basalt events

The formation of
large igneous province Image:Flood_Basalt_Map.jpg, 300px, Only a few of the largest large igneous provinces appear (coloured dark purple) on this geological map, which depicts crustal geologic provinces as seen in seismic refraction data A large igneous province (LIP) ...
s by flood basalt events could have: * produced dust and
particulate Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM), or suspended particulate matter (SPM) – are microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπ ...
aerosols which inhibited photosynthesis and thus caused
food chain A food chain is a linear network of links in a food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is Consumer-resource sy ...

food chain
s to collapse both on land and at sea * emitted sulfur oxides which were precipitated as
acid rain Acid rain is a rain or any other form of Precipitation (meteorology), precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals, and infras ...
and poisoned many organisms, contributing further to the collapse of food chains * emitted
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
and thus possibly causing once the dust and particulate aerosols dissipated. Flood basalt events occur as pulses of activity punctuated by dormant periods. As a result, they are likely to cause the climate to oscillate between cooling and warming, but with an overall trend towards warming as the carbon dioxide they emit can stay in the atmosphere for hundreds of years. It is speculated that massive volcanism caused or contributed to the End-Permian, End-Triassic and End-Cretaceous extinctions. The correlation between gigantic volcanic events expressed in the large igneous provinces and mass extinctions was shown for the last 260 million years. Recently such possible correlation was extended across the whole Phanerozoic Eon.


Sea-level falls

These are often clearly marked by worldwide sequences of contemporaneous sediments which show all or part of a transition from sea-bed to tidal zone to beach to dry land – and where there is no evidence that the rocks in the relevant areas were raised by geological processes such as
orogeny Orogeny is the primary mechanism by which mountains are formed on continents. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. This leads to both structural deformation Deformation ...
. Sea-level falls could reduce the continental shelf area (the most productive part of the oceans) sufficiently to cause a marine mass extinction, and could disrupt weather patterns enough to cause extinctions on land. But sea-level falls are very probably the result of other events, such as sustained
global cooling thumb Global cooling was a conjecture, especially during the 1970s, of imminent cooling of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land con ...

global cooling
or the sinking of the
mid-ocean ridges A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics File:Earth cutaway schematic-en.svg, upright=1.35, Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate ...
. Sea-level falls are associated with most of the mass extinctions, including all of the "Big Five"— End-Ordovician,
Late Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
, End-Permian, End-Triassic, and End-Cretaceous. A 2008 study, published in the journal ''Nature'', established a relationship between the speed of mass extinction events and changes in sea level and sediment. The study suggests changes in ocean environments related to sea level exert a driving influence on rates of extinction, and generally determine the composition of life in the oceans.


Impact events

The impact of a sufficiently large asteroid or comet could have caused
food chain A food chain is a linear network of links in a food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is Consumer-resource sy ...

food chain
s to collapse both on land and at sea by producing dust and
particulate Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM), or suspended particulate matter (SPM) – are microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπ ...
aerosols and thus inhibiting photosynthesis. Impacts on
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
-rich rocks could have emitted sulfur oxides precipitating as poisonous
acid rain Acid rain is a rain or any other form of Precipitation (meteorology), precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals, and infras ...
, contributing further to the collapse of food chains. Such impacts could also have caused
megatsunami A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water. Megatsunamis have quite different features from other, more usual types of tsunamis. Most tsunamis are caused by underwater plate tectonic ...
s and/or global
forest fire A wildfire, bushfire, wildland fire or rural fire is an unplanned, unwanted, uncontrolled fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction ...

forest fire
s. Most paleontologists now agree that an asteroid did hit the Earth about 66 Ma, but there is an ongoing dispute whether the impact was the sole cause of the
Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden of three-quarters of the and on , approximately 66 million years ago. With the exception of some species such as ...
. Nonetheless, in October 2019, researchers reported that the Cretaceous Chicxulub asteroid impact that resulted in the
extinction Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biol ...
of non-avian
dinosaurs Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution o ...

dinosaurs
66 Ma, also rapidly acidified the oceans producing
ecological collapse Ecological collapse refers to a situation where an ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together t ...
and long-lasting effects on the climate, and was a key reason for end-Cretaceous mass extinction. According to the Shiva Hypothesis, the Earth is subject to increased asteroid impacts about once every 27 million years because of the Sun's passage through the plane of the Milky Way galaxy, thus causing extinction events at 27 million year intervals. Some evidence for this hypothesis has emerged in both marine and non-marine contexts. Alternatively, the Sun's passage through the higher density spiral arms of the galaxy could coincide with mass extinction on Earth, perhaps due to increased impact events.However, a reanalysis of the effects of the Sun's transit through the spiral structure based on CO data has failed to find a correlation.


Global cooling

Sustained and significant global cooling could kill many Polar circle, polar and temperate species and force others to migrate towards the equator; reduce the area available for Tropics, tropical species; often make the Earth's climate more arid on average, mainly by locking up more of the planet's water in ice and snow. The
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...
cycles of the current ice age are believed to have had only a very mild impact on biodiversity, so the mere existence of a significant cooling is not sufficient on its own to explain a mass extinction. It has been suggested that global cooling caused or contributed to the End-Ordovician, Permian–Triassic extinction event, Permian–Triassic,
Late Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, ...
extinctions, and possibly others. Sustained global cooling is distinguished from the temporary climatic effects of flood basalt events or impacts.


Global warming

This would have the opposite effects: expand the area available for Tropics, tropical species; kill temperate species or force them to migrate towards the Polar circle, poles; possibly cause severe extinctions of polar species; often make the Earth's climate wetter on average, mainly by melting ice and snow and thus increasing the volume of the water cycle. It might also cause anoxic events in the oceans (see below). Global warming as a cause of mass extinction is supported by several recent studies. The most dramatic example of sustained warming is the Paleocene–Eocene Thermal Maximum, which was associated with one of the smaller mass extinctions. It has also been suggested to have caused the
Triassic–Jurassic extinction event The Triassic–Jurassic (Tr-J) extinction event, sometimes called the end-Triassic extinction, marks the boundary between the Triassic The Triassic ( ) is a geologic period A geological period is one of the several subdivisions of geologic time ...
, during which 20% of all marine families became extinct. Furthermore, the
Permian–Triassic extinction event The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian The Permian ( ) is a geologic period ...
has been suggested to have been caused by warming.


Clathrate gun hypothesis

Clathrates are composites in which a lattice of one substance forms a cage around another. Methane clathrates (in which water molecules are the cage) form on continental shelf, continental shelves. These clathrates are likely to break up rapidly and release the methane if the temperature rises quickly or the pressure on them drops quickly—for example in response to sudden
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been , but the current changes are more rapid than any known events in Earth's history. The main cau ...

global warming
or a sudden drop in sea level or even earthquakes. Methane is a much more powerful greenhouse effect, greenhouse gas than carbon dioxide, so a methane eruption ("clathrate gun") could cause rapid global warming or make it much more severe if the eruption was itself caused by global warming. The most likely signature of such a methane eruption would be a sudden decrease in the Isotope analysis, ratio of carbon-13 to carbon-12 in sediments, since methane clathrates are low in carbon-13; but the change would have to be very large, as other events can also reduce the percentage of carbon-13. It has been suggested that "clathrate gun" methane eruptions were involved in the end-Permian extinction ("the Great Dying") and in the Paleocene–Eocene Thermal Maximum, which was associated with one of the smaller mass extinctions.


Anoxic events

Anoxic events are situations in which the middle and even the upper layers of the ocean become deficient or totally lacking in oxygen. Their causes are complex and controversial, but all known instances are associated with severe and sustained global warming, mostly caused by sustained massive volcanism. It has been suggested that anoxic events caused or contributed to the Ordovician–Silurian extinction events, Ordovician–Silurian, Late Devonian extinction, late Devonian, Permian–Triassic extinction event, Permian–Triassic and Triassic–Jurassic extinction event, Triassic–Jurassic extinctions, as well as a number of lesser extinctions (such as the Ireviken event, Ireviken, Mulde event, Mulde, Lau event, Lau, Toarcian turnover, Toarcian and Cenomanian-Turonian boundary event, Cenomanian–Turonian events). On the other hand, there are widespread black shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. The bio-availability of Essential trace element, essential trace elements (in particular selenium) to potentially lethal lows has been shown to coincide with, and likely have contributed to, at least three mass extinction events in the oceans, that is, at the end of the Ordovician, during the Middle and Late Devonian, and at the end of the Triassic. During periods of low oxygen concentrations very soluble selenate (Se6+) is converted into much less soluble selenide (Se2-), elemental Se and organo-selenium complexes. Bio-availability of selenium during these extinction events dropped to about 1% of the current oceanic concentration, a level that has been proven lethal to many Extant taxon, extant organisms. British oceanologist and atmospheric scientist, Andrew Watson (scientist), Andrew Watson, explained that, while the Holocene, Holocene epoch exhibits many processes reminiscent of those that have contributed to past anoxic events, full-scale ocean anoxia would take "thousands of years to develop".


Hydrogen sulfide emissions from the seas

Kump, Pavlov and Arthur (2005) have proposed that during the
Permian–Triassic extinction event The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian The Permian ( ) is a geologic period ...
the warming also upset the oceanic balance between photosynthesising plankton and deep-water sulfate-reducing bacteria, causing massive emissions of hydrogen sulfide which poisoned life on both land and sea and severely weakened the ozone layer, exposing much of the life that still remained to fatal levels of UV radiation.


Oceanic overturn

Oceanic overturn is a disruption of thermo-haline circulation which lets surface water (which is more saline than deep water because of evaporation) sink straight down, bringing anoxic deep water to the surface and therefore killing most of the oxygen-breathing organisms which inhabit the surface and middle depths. It may occur either at the beginning or the end of a
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...
, although an overturn at the start of a glaciation is more dangerous because the preceding warm period will have created a larger volume of anoxic water. Unlike other oceanic catastrophes such as regressions (sea-level falls) and anoxic events, overturns do not leave easily identified "signatures" in rocks and are theoretical consequences of researchers' conclusions about other climatic and marine events. It has been suggested that oceanic overturn caused or contributed to the Late Devonian extinction, late Devonian and Permian–Triassic extinction event, Permian–Triassic extinctions.


A nearby nova, supernova or gamma ray burst

A nearby gamma-ray burst (less than 6000 light-years away) would be powerful enough to destroy the Earth's ozone layer, leaving organisms vulnerable to Ultraviolet, ultraviolet radiation from the Sun. Gamma ray bursts are fairly rare, occurring only a few times in a given galaxy per million years. It has been suggested that a supernova or gamma ray burst caused the End-Ordovician extinction.


Geomagnetic reversal

One theory is that periods of increased geomagnetic reversals will weaken Earth's magnetic field long enough to expose the atmosphere to the solar winds, causing oxygen ions to escape the atmosphere in a rate increased by 3–4 orders, resulting in a disastrous decrease in oxygen.


Plate tectonics

Movement of the continents into some configurations can cause or contribute to extinctions in several ways: by initiating or ending ice ages; by changing ocean and wind currents and thus altering climate; by opening seaways or land bridges which expose previously isolated species to competition for which they are poorly adapted (for example, the extinction of most of South America's Meridiungulata, native ungulates and all of its Sparassodonta, large metatherians after the Great American Interchange, creation of a land bridge between North and South America). Occasionally continental drift creates a super-continent which includes the vast majority of Earth's land area, which in addition to the effects listed above is likely to reduce the total area of continental shelf (the most species-rich part of the ocean) and produce a vast, arid continental interior which may have extreme seasonal variations. Another theory is that the creation of the super-continent Pangaea contributed to the Permian-Triassic extinction event, End-Permian mass extinction. Pangaea was almost fully formed at the transition from mid-Permian to late-Permian, and the "Marine genus diversity" diagram at the top of this article shows a level of extinction starting at that time which might have qualified for inclusion in the "Big Five" if it were not overshadowed by the "Great Dying" at the end of the Permian.


Other hypotheses

Many other hypotheses have been proposed, such as the spread of a new disease, or simple out-competition following an especially successful biological innovation. But all have been rejected, usually for one of the following reasons: they require events or processes for which there is no evidence; they assume mechanisms which are contrary to the available evidence; they are based on other theories which have been rejected or superseded. Scientists have been concerned that human activities could cause more plants and animals to become extinct than any point in the past. Along with human-made changes in climate (see above), some of these extinctions could be caused by overhunting, overfishing, invasive species, or habitat loss. A study published in May 2017 in ''Proceedings of the National Academy of Sciences of the United States of America, Proceedings of the National Academy of Sciences'' argued that a “biological annihilation” akin to a Holocene extinction, sixth mass extinction event is underway as a result of anthropogenic causes, such as Human overpopulation, over-population and Overconsumption, over-consumption. The study suggested that as much as 50% of the number of animal individuals that once lived on Earth were already extinct, threatening the basis for human existence too.


Future biosphere extinction/sterilization

The eventual warming and expanding of the Sun, combined with the eventual decline of atmospheric carbon dioxide could actually cause an even greater mass extinction, having the potential to wipe out even microbes (in other words, the Earth is completely sterilized), where rising global temperatures caused by the expanding Sun will gradually increase the rate of weathering, which in turn removes more and more carbon dioxide from the atmosphere. When carbon dioxide levels get too low (perhaps at 50 ppm), all plant life will die out, although simpler plants like grasses and mosses can survive much longer, until levels drop to 10 ppm. With all photosynthetic organisms gone, atmospheric oxygen can no longer be replenished, and is eventually removed by chemical reactions in the atmosphere, perhaps from volcanic eruptions. Eventually the loss of oxygen will cause all remaining aerobic life to die out via asphyxiation, leaving behind only simple anaerobic prokaryotes. When the Sun becomes 10% brighter in about a billion years, Earth will suffer a moist greenhouse effect resulting in its oceans boiling away, while the Earth's liquid outer core cools due to the inner core's expansion and causes the Earth's magnetic field to shut down. In the absence of a magnetic field, charged particles from the Sun will deplete the atmosphere and further increase the Earth's temperature to an average of ~420 K (147 °C, 296 °F) in 2.8 billion years, causing the last remaining life on Earth to die out. This is the most extreme instance of a climate-caused extinction event. Since this will only happen late in the Sun's life, such will cause the final mass extinction in Earth's history (albeit a very long extinction event).


Effects and recovery

The impact of mass extinction events varied widely. After a major extinction event, usually only weed#Weeds as adaptable species, weedy species survive due to their ability to live in diverse habitats. Later, species diversify and occupy empty niches. Generally, it takes millions of years for
biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near ...

biodiversity
to recover after extinction events. In the most severe mass extinctions it may take 15 to 30 million years. The worst event, the Permian–Triassic extinction event, Permian–Triassic extinction, devastated life on earth, killing over 90% of species. Life seemed to recover quickly after the P-T extinction, but this was mostly in the form of pioneer organism, disaster taxa, such as the hardy ''Lystrosaurus''. The most recent research indicates that the specialized animals that formed complex ecosystems, with high biodiversity, complex food webs and a variety of niches, took much longer to recover. It is thought that this long recovery was due to successive waves of extinction which inhibited recovery, as well as prolonged environmental stress which continued into the Early Triassic. Recent research indicates that recovery did not begin until the start of the mid-Triassic, 4M to 6M years after the extinction; and some writers estimate that the recovery was not complete until 30M years after the P-T extinction, that is, in the late Triassic. Subsequent to the P-T extinction, there was an increase in provincialization, with species occupying smaller ranges – perhaps removing incumbents from niches and setting the stage for an eventual rediversification. The effects of mass extinctions on plants are somewhat harder to quantify, given the biases inherent in the plant fossil record. Some mass extinctions (such as the end-Permian) were equally catastrophic for plants, whereas others, such as the end-Devonian, did not affect the flora.


See also

* Bioevent * Elvis taxon * Endangered species * Geologic time scale * Global catastrophic risk *
Holocene extinction The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (geology), epoch (with the more recent time sometimes called Anthr ...
* Human extinction * Kačák Event * Lazarus taxon * List of impact craters on Earth * List of largest volcanic eruptions * List of possible impact structures on Earth * Medea hypothesis * Rare species * Signor–Lipps effect * Snowball Earth * The Sixth Extinction: An Unnatural History, ''The Sixth Extinction: An Unnatural History'' (nonfiction book) * Speculative evolution: For instances of hypothetical animals that could one day inhabit the Earth in the distant future, especially after the Holocene extinction event. * Timeline of extinctions in the Holocene


Explanatory notes


Citations


Further reading

*


External links


Calculate the effects of an Impact

Species Alliance (nonprofit organization producing a documentary about Mass Extinction titled "Call of Life: Facing the Mass Extinction")



Sepkoski's Global Genus Database of Marine Animals
– Calculate extinction rates for yourself! {{DEFAULTSORT:Extinction Event Extinction events, Hypothetical impact events, * History of climate variability and change Doomsday scenarios Evolutionary biology Meteorological hypotheses Natural disasters