During Earth's 4.6 billion year history, life has experienced five mass extinctions. These are known as the "Big Five."
Conventionally, the causes of these extinction events were thought to be "meteorite impacts" or "unexplained climate change," but entering the 2020s, advances in mass spectrometry and geochronology have fundamentally overturned this understanding.
Recent research has revealed that many past extinctions originated from internal Earth activities, specifically massive volcanic activities known as "Large Igneous Provinces (LIPs)."
1. Late Ordovician Mass Extinction
Occurring approximately 443 million years ago, this mass extinction wiped out 85% of species. Latest research has revealed that this extinction occurred in two distinct phases (two waves) .
Ordovician Trilobite
First Wave: Cooling
Until now, the cause of this extinction was explained as "the onset of an ice age due to the movement of Gondwana," but why the cooling happened so suddenly remained a mystery for years. However, recent research is identifying the true culprit.
"Mercury anomalies" consistent with this period have been discovered in strata around the world. Mercury is the fingerprint of large-scale volcanic activity. Research since 2022 has identified the massive eruption of the "Alborz Large Igneous Province (Alborz LIP)," which existed from present-day northern Iran to Australia.
As the basalt released by this massive eruption weathered, it rapidly absorbed carbon dioxide (CO₂) from the atmosphere. This "rapid removal of CO₂" is believed to be the true cause that cooled the Earth and triggered the ice age.
Second Wave: Warming and Anoxia
The extinction event did not end with cooling alone. About 500,000 to 1 million years later, at the end of the ice age, rapid warming occurred. As glaciers melted and sea levels rose, oxygen-poor water from the seabed flowed into the continental shelves, causing widespread "oceanic anoxic events."
Creatures that had adapted to survive the cooling of the first wave could not withstand the opposite environmental changes of "scorching heat and lack of oxygen" in the subsequent second wave, and many perished. The background to the disappearance of flourishing brachiopods, conodonts, and trilobites was this relentless "double slap" of environmental fluctuations.
2. Late Devonian Mass Extinction
About 374 million years ago, oxygen depletion in the oceans and cooling progressed, exterminating 82% of species. Many marine organisms such as placoderms and Dunkleosteus perished, and coral reef ecosystems suffered devastating blows.
The cause of this extinction event has also long been debated, but a connection to the massive volcanic activity known as the "Viluy Traps" in Siberia has become clear.
Latest analysis has detected volcanic "mercury spikes" from the strata where the extinction occurred. The eruption of the Viluy Traps not only scattered harmful metals but also promoted the weathering of land plants through climate change. This caused massive amounts of nutrients to flow into the sea, leading to explosive plankton blooms. Oxygen was consumed to decompose their remains, causing the ocean to become "anoxic (anoxic event)" over a wide area.
Freshwater species (such as fish living in rivers and swamps), which are relatively resistant to changes in oxygen concentration, survived, but marine species suffered catastrophic damage. Following this, the advance of amphibians onto land accelerated as if to fill the empty ecosystem.
Hidden Mass Extinction: End-Capitanian (approx. 260 million years ago)
Latest Research Topic: Big Six?
Recent research has made it certain that another independent mass extinction event occurred about 8 million years before the End-Permian mass extinction. This is called the "End-Capitanian Mass Extinction," and discussions are underway to call it the "Big Six" in addition to the "Big Five."
In the middle of the Permian, the Emeishan Large Igneous Province (Emeishan LIP) in southwestern China erupted. A characteristic of this eruption was that the magma penetrated sedimentary layers such as limestone, generating massive amounts of "methane," a potent greenhouse gas.
This caused the extinction of about 60% of marine species, and in particular, corals, fusulinids, and the large-headed reptiles "Dinocephalians" disappeared from the Earth. This event was the prelude to the worst extinction in history that would follow.
3. End-Permian Mass Extinction
This mass extinction occurred about 252 million years ago. It is believed that 95% of marine organisms and over 90% of all species went extinct, and it is also called "The Great Dying." Trilobites went completely extinct at this time, and over 95% of ammonite genera disappeared.
The cause was the "Siberian Traps," one of the largest volcanic activities in history that occurred in Siberia, but recent research depicts an even more terrifying scenario.
Accomplice relationship between microbes and nickel: Massive amounts of "nickel" released from the Siberian volcanoes rained down into the ocean, causing an explosive proliferation of "methanogens (a type of archaea)" that feed on it. The leading theory (Rothman hypothesis) is that the methane gas they emitted caused warming far more intense than volcanic activity alone.
Furthermore, as magma burned through underground coal and rock salt layers, toxic halogen gases were generated, destroying the ozone layer. Intense ultraviolet rays rained down on the ground, collapsing terrestrial forests and ecosystems. The Siberian lava covered an area 19 times the size of Japan's landmass, but its influence extended to the other side of the globe through chemical chain reactions, driving life into a corner.
4. End-Triassic Mass Extinction
Synapsid (mammal-like reptile) that lived in the Early Triassic
About 201 million years ago, large-scale volcanic activity associated with the breakup of the supercontinent Pangea (CAMP: Central Atlantic Magmatic Province) occurred, causing 76% of species to go extinct. Conventionally, "warming" was considered the main cause, but recent research (2024-2025) points to the importance of "volcanic winter."
Volcanic activity did not drag on for millions of years but occurred as intense pulses on the scale of centuries. While the initially released carbon dioxide caused global warming through the greenhouse effect, oxygen levels dropped, dealing a blow to large animals with high metabolic rates. High temperatures dried up inland water bodies, depriving amphibians living near water of their habitats.
Subsequently, sulfur aerosols formed by the reaction of sulfur dioxide released by volcanic activity in the air blocked sunlight, plunging the Earth into rapid cooling (winter). Dominant reptiles such as the ancestors of crocodiles (Pseudosuchia), which were adapted to the tropics, could not withstand this cold and went extinct.
On the other hand, dinosaurs at that time were still minor players, but because they had already acquired feathers, they were able to endure this sudden cold snap. Having survived the "one-two punch of cooling and heating," dinosaurs explosively diversified in the world without rivals and became the rulers of the Jurassic.
5. End-Cretaceous Mass Extinction
This is the mass extinction of about 66 million years ago. Dinosaurs, pterosaurs, marine reptiles, ammonites, etc., went extinct, and 70% of species disappeared. For many years, debate continued between the "asteroid impact theory" and the "Deccan Traps volcano theory" in India, but definitive evidence was found in 2024.
Analysis of isotopes of the element "ruthenium" contained in the extinction layer revealed that its composition did not originate from Earth's volcanoes but completely matched the components of a meteorite "carbonaceous chondrite (C-type asteroid)" that flew from far away.
This confirmed that the direct trigger for the extinction was undoubtedly an asteroid impact. The volcanic activity of the Deccan Traps was also deteriorating the environment, but it was the asteroid that delivered the final blow.
A type of ammonite that lived in the Cretaceous. From France
(*Note) Regarding the extinction timing of ammonites, while there is no doubt they went extinct due to the climate change from the meteorite impact, fossils suggesting that they survived for tens of thousands to hundreds of thousands of years after the impact have been found in some regions.
6. The Mass Extinction Currently Underway
It is said that we are currently in the midst of the sixth mass extinction. Unlike past volcanoes and meteorites, the cause is due to the activities of us humans (Homo sapiens).
However, the latest statistical data (2025) highlights an aspect different from simple "acceleration of extinction." Most of the recorded extinctions peaked in the early 1900s, and the majority were cases where endemic species on "islands" were exterminated by invasive species.
The true crisis we face now is that due to habitat destruction and climate change in continental areas, many organisms are in a state of "endangerment." Because their numbers have plummeted and they have lost genetic diversity, their future extinction is all but guaranteed.
Research into past mass extinctions teaches us how fragile the Earth's system is and that once the balance is tipped, it takes millions of years to recover.