The Siberian Traps are a plateau of basalt—oceanic crust—measuring roughly 7 million sq km/3 million sq mi—a little smaller than Australia--in extent and 4 km/2.5 mi thick in northern Siberia. The term “trap” comes from the Swedish word “trappa”, stairs, referring to the flat, steplike volcanic deposits. They were created by giant supervolcanoes at the then-northern tip of Pangea between 300 and 250 MYA, in several series of eruptions which lasted two million years.
Location of the Siberian Traps, present day.
Siberian Traps location at time of eruption.
Supervoclanoes are on-land mantle hotspots, like Hawaii or Iceland, but beneath continental crust. Beneath the ocean they form part of the global spreading ridge system, and are erupting more or less continually. But on continents, the heat and pressure from magma and steam can build up for an initially explosive eruption before continuing to produce flood basalts. There is evidence of such ancient volcanoes in the United States—the smaller Columbia River basalts of Oregon from 200 MYA—and Yellowstone is a live modern example, though it’s likely significantly smaller than the ancient Siberian vent(s).
The Traps and neighboring coal deposits.
Paleo-carbon dioxide record (note the spike between 300 and 200 MYA).
These volcanoes emit a low-viscosity (flowing freely) lava which becomes basalt, the dense rock of the ocean floor (this is why Hawaiian eruptions become rivers of lava, and not the towering ash clouds of explosive volcanoes like Mt. St Helens or Vesuvius). The volcanoes of ancient Siberia erupted a staggering amount of fluid which spread across the land and likely the ocean floor, extending the continent with awesome horizontal rock formations. Modern research shows, however, that the Siberian eruptions might have been rather less viscous than most eruptions of this sort, with a greater pyroclastic, ash cloud component, which would have caused worse immediate climate disruption.
Schematic of a supervolcano.
Basalt cliffs in Siberia.
These mammoth eruptions led to the end of most life on earth. As much as 96% of all marine species and 70% of land species went extinct. The cause of the Permian-Triassic extinction (known by other names like the “Great Dying”) has long been a mystery to paleontologists. Current theory assigns several levels of cause to the Siberian eruptions. First was the intense global cooling due to the ash clouds from repeated eruptions. Second was, after the ash clouds had dissipated—a matter of a few years—giant coal deposits in the vicinity caught fire and added billions of tons of carbon dioxide to the atmosphere, warming the planet and acidifying the ocean. This process continued for two million years and caused the greatest extinction known in the geologic record.
More Siberian basalt, cut through by a river.
Tomorrow: the Himalaya.
Be brave, and be well.
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