Approximately 66 million years ago an asteroid wiped out the dinosaurs, leaving only fossils that demonstrate the passage of gigantic reptiles across the planet.
The giants of the past were extinguished by an asteroid that, in addition to the impact and the explosion, changed ecosystems and made life unsustainable in much of the earth.
According to a team from the California Academy of Sciences, which recently conducted an investigation, they point out that after the initial impact forest fires filled the sky and blocked the Sun shortly after the asteroid hit the planet.
The asteroid had a dimension of 12 kilometers wide and was traveling at more than 43 thousand kilometers per hour when it crashed in what is now the Gulf of Mexico.
The impact led to the extinction of 75 percent of all life on Earth, and scientists have long been studying the aftermath of this impact.
In a new study, the American team found that the main trigger for the extinction may have been ash clouds spreading through the atmosphere.
These clouds are presumed to have persisted for up to two years, putting large parts of the Earth in darkness, making it difficult for anything to grow or survive.
Life in the area surrounding the impact would have died instantly, but there was significantly more damage in the years after the collision.
This includes tidal waves, floods, and massive environmental changes, including the ejection of particles into the atmosphere, that spread throughout the world.
While the Earth was shrouded in darkness, the researchers say photosynthesis, the process plants use to grow, would have failed.
This would have led to an ecosystem collapse, and even after sunlight returned, the decline in photosynthesis would have continued for decades, the team explained in an interview with Live Science.
This atmospheric darkness was caused by pulverized rock and sulfuric acid from the crash that formed like clouds in the sky, cooling global temperatures and producing acid rain, sparking large-scale wildfires.
This “nuclear winter scenario,” as first proposed in the 1980s, played a major role in the mass extinction, study author Peter Roopnarine explained to Live Science.
Although it has been theorized for more than four decades, only in the last 10 years have models been developed to see how this darkness impacted life.
“The common thinking now is that global wildfires would have been the main source of fine soot that would have been suspended in the upper atmosphere,” Roopnarine said.
“The soot concentration in the first days or weeks of the fires would have been high enough to reduce the amount of incoming sunlight to a low enough level to prevent photosynthesis,” he added.
The team studied the long-term impact of this dark period by rebuilding the ecological communities that would have existed when the asteroid struck.
They collected 300 species that were known to have come from a fossil-rich expanse known as the Hell Creek Formation, which is made of shale and sandstone in North Dakota, South Dakota, Wyoming, and Montana.
They then created simulations to expose communities to periods of darkness of 100 to 700 days to discover what interval of darkness would lead to the level of extinction that we now know to have occurred among vertebrate species.
Fossil records show that around 73 percent of vertebrate species became extinct after the impact event.
Roopnarine told Live Science that the onset of the darkness impact would have occurred quickly, peaking within a few weeks.
Ecosystems could mostly recover if the darkness had only lasted 150 days, but after 200 days they reached a ‘critical tipping point’.
This was the point where some species became extinct and the dominance among the remaining species changed in a way that damaged the ecosystem.
When darkness lasted up to 700 days, extinctions increased dramatically, reaching up to 81 percent of all life, suggesting that animals in the Hell Creek communities experienced approximately two years of darkness.
The findings are preliminary, he explained, and only explore a single ecosystem, but suggest that this could impact more species.
The findings were presented at the American Geophysical Union (AGU) annual meeting.