Did meteorites wipe out mammoths? Clues from Texas cave suggest volcanic eruptions may have caused extinction
Researches claim that volcanic eruptions, along with cooling of the oceans and more snow cover, were the likely culprits
A Texas cave holds records of the events that may have triggered a sudden climate change about 13,000 years ago. The "global cooling" may have wiped out mammoths and several other species at that time. Now, in a new study, researchers have ruled out meteorites as the cause.
Instead, they suggest, volcanic eruptions were the likely culprits. The aerosols present in them may have blocked the sun's radiation. Other factors such as cooling of the oceans and more snow cover could have driven the change, according to researchers from the University of Houston, Baylor University, and Texas A&M University. They found no evidence implicating an extraterrestrial object hitting or bursting over Earth at that time, Dr Alan Brandon from Baylor University and corresponding author of the study, told MEA WorldWide (MEAWW).
"The cooling period, known as the Younger Dryas, disrupted a general warming trend at the end of the Pleistocene era," said Nan Sun, a doctoral student at the University of Houston's Department of Earth and Atmospheric Sciences and first author of the study. The epoch is the Last Ice Age, following which the Earth began warming. Interrupting these changes was the Younger Dryas period, which lasted 1,200 years. It saw temperatures drop by about 3 degrees celsius. Evidence on the cause from the locality indicated a comet impact, but details were lacking, Steven L Forman, from Baylor University, told MEAWW.
“One big question was: did an extraterrestrial impact occur near the end of the last ice age, about 13,000 years ago, and cause an abrupt cooling that thrust the northern hemisphere back into the ice age for an extra 1,200 years?” Dr Michael Waters, from Texas A&M University, wondered.
So a group of researchers got together to address the question by excavating Hall's Cave located in Texas hill country. The site has a sediment record extending over 20,000 years, according to them. They chemically analyzed these sediments to determine the proportion of elements such as iridium, ruthenium, platinum, palladium, and rhenium. Their signatures were then compared to those containing materials added by a meteor, asteroid, or other objects from space when it crashed into Earth.
But it matched those present in volcanic gases. "It was terrestrial. This shows that there are other mechanisms besides space objects that can cause these events. It looks like volcanoes may be much more important than people thought," Brandon explained. Next, the researchers hope to see if they can find similar signatures in other North American sites as well.
What do we know of volcanic eruptions and climate change?
In 1991, the major Pinatubo eruption in the Philippines -- also the second-largest of the century -- saw cooling for a week or so. However, according to Dr. Brandon, it takes a very big volcanic eruption or series of them to cause a short-term climate change (years to 100s of years). Dr Forman said, "Our planet’s response to internal climate perturbations (like increase in CO2) is not linear, but can be rapid and to an extreme state, like the Younger Dryas period."
The study was published in Science Advances.