Tag: Asteroid impact (Chicxulub)

Mass extinctions are periods in Earth’s history when a large percentage of species die out in a relatively short geological time (typically thousands to a few hundred thousand years), far above the normal “background” extinction rate.

Paleontologists recognize five major mass extinctions (the “Big Five”) over the past ~540 million years (the Phanerozoic Eon). These events reshaped life on Earth and opened ecological opportunities for surviving groups.

The Big Five Mass Extinctions

Event	Time (approx.)	Species Lost (est.)	Main Causes	Key Victims
End- Ordovician	444 million years ago	~85%	Rapid glaciation & sea- level fall, then warming	Marine invertebrates (graptolites, trilobites, brachiopods)
Late Devonian	372- 359 million years ago	~70- 75%	Climate cooling, ocean anoxia, possible volcanism or impacts	Reef-building organisms, many marine groups, early fish
End- Permian (“The Great Dying”)	252 million years ago	~90- 96% (marine), ~70% (terrestrial)	Massive Siberian Traps volcanism → global warming, ocean acidification, anoxia	Most marine life, many land vertebrates, insects, plants
End-Triassic	201 million years ago	~70- 80%	Central Atlantic Magmatic Province volcanism → climate change & ocean chemistry shifts	Many marine groups, early reptiles, some amphibians
End- Cretaceous (K- Pg)	66 million years ago	~75%	Asteroid impact (Chicxulub) and Deccan Traps volcanism	Non- avian dinosaurs, pterosaurs, ammonites, many marine reptiles

Notes on severity:

• The End- Permian was by far the most severe, the closest life has come to total annihilation.
• The End- Cretaceous is the best- known because it ended the age of dinosaurs and allowed mammals (and eventually humans) to diversify.

Most mass extinctions involved rapid environmental upheaval, often triggered by:

• Large Igneous Province (LIP) volcanic eruptions (releasing CO₂, SO₂, and other gases)
• Asteroid/comet impacts (confirmed mainly for the K- Pg event)
• Climate shifts (cooling or extreme warming)
• Ocean anoxia, acidification, or sea- level changes

These ultimate triggers created proximate “kill mechanisms” such as temperature extremes, loss of oxygen in the oceans, acid rain, and disruption of food webs.

Many scientists argue that we are currently in the early stages of a sixth mass extinction, driven by human activities (habitat destruction, climate change, pollution, overexploitation, and invasive species).

Current extinction rates for vertebrates and other groups are estimated to be tens to hundreds of times higher than background rates. While we have not yet reached the classic threshold of ~75% species loss, the trajectory is accelerating and is considered by many researchers to meet the definition of a mass extinction in progress (often called the Holocene or Anthropocene extinction).

Mass extinctions are rare but transformative events. Each one permanently altered the course of evolution, eliminating dominant groups and allowing survivors to radiate into vacant ecological niches.

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Large Igneous Provinces (LIPs) are among the most extreme volcanic events in Earth’s history. They involve the rapid emplacement of enormous volumes of mostly mafic (basalt- rich) magma, far larger than ordinary volcanoes or even flood- basalt fields produced by typical hotspot activity.

A standard modern definition describes LIPs as magmatic provinces with:

• Areal extent greater than ~100,000 km²
• Igneous volume greater than ~100,000 km³ (often millions of km³)
• Emplacement mainly in short pulses lasting 1- 5 million years (sometimes with longer overall duration up to ~50 million years)
• Predominantly intraplate tectonic setting (not normal mid- ocean ridge or subduction- zone volcanism)

They produce thick stacks of flood basalts (“traps”), extensive dike and sill complexes, and sometimes oceanic plateaus. Some LIPs also include significant silicic (rhyolitic) components.

Famous Examples

LIP	Age (approx.)	Location	Notes / Associated Events
Siberian Traps	252 Ma	Siberia, Russia	Linked to the end-Permian mass extinction (“Great Dying”)
Central Atlantic Magmatic Province (CAMP)	201 Ma	Eastern North America, parts of Europe, Africa, South America	Linked to the end-Triassic mass extinction; associated with the breakup of Pangaea
Deccan Traps	66 Ma	Western India	Contemporaneous with the end- Cretaceous (K-Pg) extinction; combined effects with the Chicxulub impact
Paraná -Etendeka	~132 Ma	South America & southern Africa	Related to the opening of the South Atlantic
Columbia River Basalts	17- 6 Ma	Northwestern USA	Youngest major continental flood basalt province
Ontong Java Plateau	~120 Ma	Pacific Ocean	One of the largest oceanic LIPs

Other notable LIPs include the Emeishan Traps (China, ~260 Ma) and the North Atlantic Igneous Province.

The leading hypothesis involves mantle plumes, large upwellings of hot material from deep in the mantle (possibly the core- mantle boundary). When a plume head reaches the base of the lithosphere, it causes widespread melting and massive magma production.

Alternative or complementary ideas include lithospheric extension, edge- driven convection, or interactions with subducted material. Many LIPs are associated with continental breakup.

LIPs can release vast quantities of volcanic gases (especially CO₂, SO₂, and halogens) plus additional gases from heating surrounding sedimentary rocks (thermogenic gases). These emissions can drive:

• Rapid global warming (from CO₂)
• Short- term cooling (from sulfate aerosols)
• Ocean acidification and anoxia
• Acid rain
• Possible ozone depletion

Because of these effects, LIPs are strongly linked to several of the “Big Five” mass extinctions and many lesser biotic crises. The Siberian Traps, CAMP, and Deccan Traps are the clearest examples of this connection.

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The End- Cretaceous (K- Pg or Cretaceous- Paleogene) mass extinction occurred approximately 66 million years ago. It is the most recent of the “Big Five” mass extinctions and the event that ended the reign of the non- avian dinosaurs.

Scale of the Extinction

• Roughly 75% of species went extinct.
• Major losses included:
  • All non- avian dinosaurs
  • Pterosaurs
  • Marine reptiles (mosasaurs, plesiosaurs)
  • Ammonites and many other marine invertebrates
  • Significant losses among plants, plankton, and other groups
• Survivors included birds (the only remaining dinosaur lineage), mammals, crocodilians, turtles, lizards, snakes, amphibians, and many plant groups. These survivors later diversified dramatically in the Paleogene.

The Two Major Events

Two large-scale perturbations occurred around the same time:

1. Chicxulub Asteroid Impact

• A ~10- 15 km asteroid struck the Yucatán Peninsula (Mexico), creating the ~180- 200 km Chicxulub crater.
• Immediate effects: massive earthquakes, tsunamis, wildfires, and a global “impact winter” caused by dust, soot, and sulfate aerosols blocking sunlight for months to years.
• This led to the collapse of photosynthesis, rapid cooling, and the breakdown of food webs on land and in the oceans.
• The impact is widely accepted as the primary trigger for the abrupt, global extinction.

2. Deccan Traps Volcanism (a Large Igneous Province)

• Massive flood- basalt eruptions in what is now western India produced ~1 million km³ of lava over roughly 700,000- 800,000 years, spanning the K- Pg boundary.
• These eruptions released large volumes of CO₂ (causing warming) and SO₂ (causing short- term cooling and acid rain).
• Activity began before the impact and continued afterward. Some evidence suggests the impact itself may have intensified later eruptive phases through seismic triggering.

Most researchers agree that the Chicxulub impact was the decisive kill mechanism that produced the sudden, global extinction pattern seen in the fossil record.

The Deccan Traps likely stressed ecosystems beforehand (through climate fluctuations) and may have contributed to the overall severity, but modeling studies indicate that Deccan volcanism alone would not have caused the extinction of the non- avian dinosaurs. In some scenarios, the long- term CO₂ warming from the Deccan Traps may even have partially buffered the extreme cold of the impact winter.

The combination is sometimes described as a “press- pulse” scenario: prolonged volcanic stress (the press) followed by the catastrophic impact (the pulse).

Ecosystems began recovering relatively quickly in some regions (within tens of thousands of years for primary productivity), though full recovery of diversity took much longer. Mammals, in particular, underwent a major adaptive radiation in the ecological space left vacant by the dinosaurs, eventually leading to the rise of larger forms and, much later, primates and humans.

This event marks the boundary between the Mesozoic and Cenozoic Eras and remains one of the best-studied mass extinctions due to the clear geological markers (the iridium- rich boundary layer, shocked quartz, and the Chicxulub crater itself).

By the way, the Chicxulub asteroid impact did not start (activate from nothing) the Deccan Traps volcanism.

The Deccan Traps eruptions were already underway for hundreds of thousands of years before the impact. High- precision dating shows that Deccan volcanism began well before the Cretaceous- Paleogene (K- Pg) boundary.

However, there is a credible scientific hypothesis that the Chicxulub impact intensified or triggered the largest and most voluminous phase of the Deccan eruptions.

Key points supporting this idea:

• Around the time of the impact (~66 million years ago), the Deccan Traps experienced a major “state shift.” The eruptions became larger, more episodic, and much more voluminous.
• The most massive lava flows (the Wai Subgroup: Poladpur, Ambenali, and Mahabaleshwar formations) account for roughly 70% of the main- stage volume of the Deccan Traps. High- precision dating places the start of this major pulse within about 50,000 years of the Chicxulub impact (essentially simultaneous within dating precision).
• The impact would have generated enormous seismic energy, equivalent to a magnitude ~10-11 earthquake. Modeling shows this seismic energy could have traveled through the mantle and increased the permeability of the existing magmatic system beneath India, allowing a large volume of already-generated magma to erupt more rapidly.

This idea was formally proposed in papers by Richards et al. (2015) and Renne et al. (2015) and remains an active area of research. It is supported by the close timing, changes in eruption style and geochemistry, and analogies with historical earthquakes that have triggered volcanic eruptions.

The Deccan Traps were already active independently (linked to the Réunion mantle plume).

The Chicxulub impact is the primary cause of the mass extinction.

It is plausible (but not universally accepted as proven) that the impact’s seismic waves amplified the ongoing Deccan volcanism, leading to the most intense eruptive phase right around the extinction boundary.

In short: The impact did not create the Deccan Traps, but it may have “shaken the can” and caused the biggest eruptions to happen at the worst possible time.