Thursday, September 3, 2015

The End of the World, 252 Million Years Ago

Fig.1. This trilobite was part of an important class of extinct animals that one ruled the seas (Credit: Kevin Walsh, 2005 via Flickr

Have you ever wondered about the curious creatures behind #trilobitetuesday? These marine arthropods roamed the oceans for over 270 million years and are widely considered to be among the most successful of early animals. Trilobites are well preserved and make up a large number of marine invertebrate fossil collections, informing on research in fields as wide ranging as evolutionary biology to plate tectonics. They ultimately went extinct at the end of the Permian period around 252 million years ago - along with more than 90 percent of ocean species and 75 percent of land species - during the most massive extinction event in the paleontological record. Although causes have been attributed to anything from asteroids to sea-floor methane, a recently published paper in Science Advances argues that volcanic activity catalyzed the catastrophic Permian-Triassic extinction event.

Volcanoes and the End of the World

MIT researchers Seth Burgess and Samuel Bowring used hundreds of rock samples from across 2.5 million square miles in Siberia, Russia, to precisely date volcanic actively from millions of years ago. This region is home to the Siberian Traps, a vast region of volcanic rock formed by many ancient volcanoes releasing around 4 million cubic kilometers of magma. Burgess and Bowring extracted crystals from these rocks and used radioactive dating techniques to create an accurate timeline of the extensive eruptions.

Fig.2. Physical map of Siberia with extent of Siberian Traps (Credit: Ulamm, 2008)

They found that the eruptions began approximately 300,000 years before the Permian-Triassic extinction event and then continued for another half million years. Such eruptions would have spewed high levels of carbon dioxide and other gases into the atmosphere which, highlighted previously, could have caused rampant ocean acidification and an increase in temperatures. Burgess and Bowring hypothesize that the massive amounts of atmospheric greenhouse gases drove climate change and completely destabilized the biosphere. The unusually long recovery period of 5 to 10 million years suggests that continued pulses of magmatism prevented ecosystems from fully restructuring after extinction.

Upsetting the Balance

From the “Year Without a Summer” to Mount St. Helens, regional cooling and ecosystem upheaval are just a few effects volcanoes have on the world around them. Eruptions in recent history are well recorded, but understanding 250 million years ago is more difficult. Burgess and Bowring studied rock samples and drill cores that stood the test of time. The fossil record also shows a sudden drop of diversity in animals, from terrestrial fossil sites to marine animals found in sediment cores.Together, rock and animal remnants reveal a valuable analysis of ancient ecosystems. The ability to precisely date environmental records allows a more exact understanding of prehistoric species shifts, and how even the most successful of animals may one day go extinct

Burgess, S. D., & Bowring, S. A. (2015, August 7). High-precision geochronology confirms voluminous magmatism before, during, and after Earth’s most severe extinction. Science Advances, vol. 1 (7): e1500470. doi: 10.1126/sciadv.1500470

Hoffman, H. J. (2000). The Permian Extinction - When Life Nearly Came to an End. National Geographic. Retrieved from:


Permian period
A geologic period which extended from around 300 to 252 million years ago, preceding the Triassic.
Permian-Triassic extinction event
The most extensive extinction event recorded in paleontology that caused around 90 percent of marine species and 75 percent of land organisms to go extinct. This event occurred around 252 million years ago.
The formation of igneous rocks from magma.

No comments :

Post a Comment