The dead center of Russia, far away from any tectonic plate boundaries, is a massive flood plain of basalt rock the size of western Europe. How did ten trillion tons of lava come to form the igneous province now called the Siberian Traps? However it happened, it’s by far the biggest crime scene in history, since its formation killed off more than 90 percent of all life on Earth.
Nothing is trapped in the Siberian Traps.
Almost a million square miles of Siberia are covered with the telltale stair-step hills made by floods of basaltic lava, which is how the region got its name—trappa is the Swedish word for stairs. For about a million years, lava and pyroclastic rock vented out of the earth here, sometimes explosively. In all, about one million cubic miles of molten rock were ejected. To get your mind around an eruption that big, try imagining cubes of lava one thousand miles on each side. Yeah, I can’t do it either.
It came from the earth’s core!
How does this much volcanic activity happen so far away from plate boundaries? In 1963, geologists first proposed a mechanism called a mantle plume: a jet of hot rock that might begin way down at the core-mantle boundary 2,000 miles below our feet, and eventually rise by convection all the way to the surface. If a plume like this one stayed anchored for millions of years, constantly spewing out lava while plates and continents moved above it, it could explain the formation of island chains like Hawaii.
Or…it came from outer space!
Other scientists have their own twist on the mantle plume theory: What if an impact event triggered all the volcanic chaos? The Siberian Traps are almost exactly antipodal to the Wilkes Land crater, a giant impact crater that many scientists believe hides beneath the ice sheets of Antarctica. Could a comet or asteroid have struck Antarctica so hard that lava started jetting out all the way on the other side of the planet, like smacking a choking friend on the back so hard that a bit of stuck hot dog comes flying out of their mouth? (In this analogy, the hot dog bits keep flying for about one million years.)
The Siberian Traps are the world’s biggest tombstone.
Scientists now believe that just one year of spewing Siberian lava could have put 1.5 billion tons of sulfur dioxide into the earth’s atmosphere—and keep in mind that the eruption continued for one million years. That’s why the Siberian Traps are now the prime suspect behind the mass extinction that ended the Paleozoic Era about 250 million years ago. This death-fest dwarfs the one that would later kill the dinosaurs; even fish and insects were hard hit. Scientists guess that 96 percent of marine species and 70 percent of land species were completely wiped out. If you haven’t seen a trilobite lately, blame Siberia.
Explore the world’s oddities every week with Ken Jennings, and check out his book Maphead for more geography trivia.