Asteroid impact that killed the dinosaurs sparked two years of darkness

The asteroid impact that wiped out most of the dinosaurs 66 million years ago sparked two years of darkness caused by the soot from raging wildfires that filled the sky and blocked the sun.

This phenomenon further contributed to the wave of extinctions that followed. The findings were presented at the annual meeting of the American Geophysical Union (AGU).

Environmental impact from asteroid impact

While the cataclysm caused by the asteroid impact extinguished many life forms almost instantly, the impact also caused environmental changes leading to mass extinctions that played out over a longer period of time. 

According to research led by the Department of Invertebrate Zoology and Geology at the California Academy of Sciences, one such extinction trigger might have been the dense cloud of ash and other particles that spread all over the planet after the asteroid impact, which enveloped many parts of the Earth in darkness for up to two years.

During that time, photosynthesis had probably failed, leading to massive environmental collapse, with at least 75 percent of life on Earth completely extinguished.

“The common thinking now is that global wildfires would have been the main source of fine soot that would have been suspended into the upper atmosphere,” said study lead author Peter Roopnarine, a curator of Geology at the California Academy of Sciences.

“The concentration of soot within the first several days to weeks of the fires would have been high enough to reduce the amount of incoming sunlight to a level low enough to prevent photosynthesis.”

Periods of darkness destroy ecosystems

Roopnarine and his colleagues believe that ecosystems could recover after a period of darkness of up to 150 days. However, after over 200 days, some species will already start going extinct and patterns of dominance will change. During a darkness interval of 650 to 700 days, extinction levels may reach 65 to 81 percent.

Since it is known that around 75 percent of the species went extinct after the asteroid impact 66 million years ago, the scientists believe that the dark period may have lasted approximately two years.

“Conditions varied across the globe because of atmospheric flow and temperature variation, but we estimated that the darkness could have persisted in the Hell Creek area [a representative, fossil-rich region dating to the latter part of the Cretaceous and extending over parts of today’s Montana, North Dakota, South Dakota and Wyoming] for up to two years,” concluded Roopnarine.

More about the asteroid that killed the dinosaurs

Around 66 million years ago, an asteroid, with a force unlike any other in Earth’s recent history, struck our planet and dramatically altered its trajectory of life. This event, often referred to as the Cretaceous-Paleogene (K-Pg) extinction event, led to the decline and eventual extinction of roughly 75% of Earth’s species, most notably the non-avian dinosaurs.

The fateful asteroid impact

This colossal asteroid, estimated to be about 10 kilometers (6 miles) in diameter, plummeted towards Earth at a blistering speed. When it collided with what is now the Yucatán Peninsula in Mexico, it created the Chicxulub crater, a massive depression more than 150 kilometers (93 miles) in diameter.

Immediate aftermath of the asteroid impact

The impact released an estimated energy equivalent to billions of atomic bombs. This tremendous force ignited wildfires hundreds of miles away and released vast amounts of sulfur into the atmosphere, leading to a significant drop in temperatures.

Earth plunged into a “nuclear winter” scenario: dark, cold, and inhospitable. The plummeting temperatures and widespread darkness, which resulted from the dust and soot released, severely disrupted the food chain. Photosynthesizing plants could not survive in such conditions, leading to a cascade of extinction events up the food chain.

Longer-term effects

But the asteroid’s impact did more than just throw up dust and soot. It also resulted in widespread acid rain, which further disrupted ecosystems. The ash from the impact blocked sunlight for an extended period, cooling the planet and disrupting the climate for several years.

Oceans didn’t escape unscathed either. The fallout from the asteroid severely affected marine ecosystems. The change in temperatures led to a decline in marine plankton, the primary food source for many marine species. The collapse of this foundational layer of the marine food chain had catastrophic effects on the marine species that depended on it.

Recovery and evolution’s new course

Although the aftermath was devastating, life proved resilient. The extinction event paved the way for mammals, which had previously lived in the shadows of the dinosaurs, to rise in prominence and diversify. These mammals would eventually evolve into a vast array of species, including humans.

Over time, the Earth’s atmosphere and climate stabilized, and life began to recover and evolve in new directions. The void left by the dinosaurs allowed for the rise of new dominant species, reshaping the evolutionary trajectory of the planet.

The asteroid that struck Earth 66 million years ago dramatically changed the course of life on our planet. While it marked the end for the dinosaurs and many other species, it also opened up evolutionary opportunities for others. The story of this asteroid serves as a stark reminder of the power of extraterrestrial events and their potential to reshape the very fabric of life on Earth.

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