THE HAGUE, May 14 -- Dutch geologists found hard evidence that the earth cooled down abruptly following an asteroid impact, earth sciences researcher Johan Vellekoop told Xinhua on Wednesday.

The mass extinction of dinosaurs and plants at the Cretaceous-Paleogene boundary 66 million years ago is thought to be caused by the impact of an asteroid at Chicxulub, in present-day Mexico.

After the asteroid clash, a so-called "impact winter" occurred, caused by the injection of large amounts of dust into the stratosphere, which blocked solar radiation and eventually led to the death of dinosaurs and most plant life.

"We proved that indeed a short period of darkness and cold started after the meteorite impact," Vellekoop told Xinhua. "This has always been the idea, but the real hard evidence was missing. We started looking for the truth behind the suspicions."

His paper on the subject will be published in the next issue of the American scientific journal Proceedings of the National Academy of Sciences (PNAS) and is already partly available on its website.

Researchers and geologists from the University of Utrecht, the VU University in Amsterdam and the Royal Netherlands Institute for Sea Research (NIOZ), have now been able to demonstrate the first direct evidence, to their knowledge, for the effects of the formation of dust and aerosols.

They documented a major decline in the sea surface temperature by looking at fossilized sediments from the Brazos River region in Texas which was a sea in ancient times.

"The sediments from Texas showed us that the meteorite clash was followed by a tsunami, which was followed by a strong cooling of the sea," Vellekoop added.

"With new technologies, we can see that the sea temperature dropped from 30 degrees Celsius to 23 degrees Celsius or even lower. That lasted a few years, not more than a few decades. When the dust started to fall again, the temperature also rose again, also notable in the sediments," he stated.

According to researchers, this "impact winter" was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis, which is a process used by plants and other organisms to convert light energy into chemical energy that can be later used to fuel the organisms' activities.

Without photosynthesis the food chain collapses, leading to the disappearance of plant and animal life.