February 11, 2014
End-Permian Extinction Was Nearly Instantaneous, According To MIT Researchers
April Flowers for redOrbit.com - Your Universe Online
Approximately 252 million years ago, the largest mass extinction event in the history of animal life on Earth occurred — wiping out more than 96 percent of marine species and 70 percent of terrestrial species. This included the largest insects known to have inhabited the planet.
Scientists have explored many theories to explain the cause of the end-Permian extinction, as it came to be known. Those theories include an asteroid impact, massive volcanic eruptions, or a cataclysmic cascade of environmental events. Pinpointing the exact cause of the mass extinction, however, requires better measurements of how long the extinction period lasted.
A research team from MIT has determined that the end-Permian extinction took place over 60,000 years — give or take 48,000 years. From a geologic perspective, that's nearly instantaneous. The new timescale, detailed in a recent issue of Proceedings of the National Academy of Sciences, is based on more precise dating techniques. These findings indicate that the most extensive extinction in history may have happened more than 10 times faster than scientists had previously thought.
"We've got the extinction nailed in absolute time and duration," says Sam Bowring, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. "How do you kill 96 percent of everything that lived in the oceans in tens of thousands of years? It could be that an exceptional extinction requires an exceptional explanation."
The team, which included MIT graduate student Seth Burgess and a colleague from the Nanjing Institute of Geology and Paleontology, also found that 10,000 years before the die-off, the oceans experienced a pulse of light carbon. This pulse most likely reflects a massive increase in carbon dioxide in the atmosphere, which may have led to widespread ocean acidification and increased sea temperatures by 50 degrees Fahrenheit or more, killing the majority of sea life.
What caused the spike in carbon dioxide in the first place? Geologists and paleontologists hypothesize that the spike had to do with widespread, long-lasting volcanic eruptions from the Siberian Traps, a region of Russia whose step-like hills are a result of repeated eruptions of magma. The researchers used similar dating techniques to establish a timescale for the Permian period's volcanic eruptions in order to establish whether eruptions from the Siberian Traps triggered the massive increase in oceanic carbon dioxide. These Permian period eruptions are estimated to have covered over five million cubic kilometers.
"It is clear that whatever triggered extinction must have acted very quickly," says Burgess, "fast enough to destabilize the biosphere before the majority of plant and animal life had time to adapt in an effort to survive."
Bowring and his students visited Meishan, China — a region whose rock formations bear evidence of the end-Permian extinction event — in 2006. The Meishan region has attracted geologists and paleontologists hoping to find clues in its layers of sedimentary rock, specifically focusing on a section of rock that is thought to delineate the end of the Permian, and the beginning of the Triassic, based on evidence such as the number of fossils found in surrounding rock layers.
The researchers took rock samples from this area, as well as from nearby alternating layers of volcanic ash and fossil-bearing rocks. These rocks were analyzed by the team who reported in 2011 that the end-Permian event likely lasted less than 200,000 years. This timeframe still wasn't precise enough to draw any conclusions about what caused the extinction, however.
The current findings revise the original estimates, using more accurate dating techniques based on a better understanding of uncertainties in timescale measurements.
The rock samples collected from five volcanic ash beds at the Permian-Triassic were reanalyzed using this new knowledge. First, the rocks were pulverized and tiny zircon crystals containing a mix of uranium and lead were separated out. The uranium was isolated from the lead, then the ratios of both isotopes were measured to determine the age of each rock sample.
The measurements allowed the research team to determine a much more precise "age model" for the end-Permian extinction, which now appears to have lasted about 60,000 years — with an uncertainty of 48,000 years. The event was immediately preceded by a sharp increase in oceanic carbon dioxide.
According to Bowring, the new timeline adds weight to the theory that the extinction was trigged by massive volcanic eruptions from the Siberian Traps that released volatile chemicals, including carbon dioxide, into the atmosphere and oceans. The short extinction timeline makes it possible that a single, catastrophic pulse of magmatic activity triggered an almost instantaneous collapse of all global ecosystems.
The researchers plan to determine an equally precise timeline for the Siberian Traps eruptions in order to confirm their role in the extinction event. This timeline will be compared to the new extinction timeline to see where the two events overlap. They also plan to investigate other areas in China to see if the duration of the extinction can be even more precisely determined.
"We've refined our approach, and now we have higher accuracy and precision," Bowring says. "You can think of it as slowly spiraling in toward the truth."