The Siberian Traps (Russian: Сибирские траппы, written in the Latin alphabet: Sibirskiye trappy) are a large area of volcanic rock, called a large igneous province, located in Siberia, Russia. A huge amount of basaltic lava covered a wide area of Siberia during a flood basalt event. The massive volcanic eruption that created the traps is one of the largest volcanic events known in the last 500 million years. The eruptions lasted about two million years and occurred around the time of the Permian–Triassic boundary, or P–T boundary, which happened approximately 251.9 million years ago. The Siberian Traps are thought to be the main cause of the Permian–Triassic extinction event, the most severe extinction in Earth's history. Later periods of activity from the Siberian Traps have been connected to smaller extinction events, including the Smithian-Spathian, Olenekian-Anisian, Middle-Late Anisian, and Anisian-Ladinian extinctions. Today, the area is covered by about 7 million square kilometers (3 million square miles) of basaltic rock, with a total volume of roughly 4 million cubic kilometers (1 million cubic miles).
Etymology
The word "trap" has been used in geology since 1785–1795 to describe certain rock structures. It comes from the Swedish word "trappa," which means "stairs." The term describes hills that form step-like shapes in the landscape of the region.
Formation
The basaltic rock found in the Siberian Traps is believed to have formed from a mantle plume, a hot area deep within the Earth that rose until it reached the base of the Earth's crust. This movement caused volcanic eruptions through the Siberian Craton. Scientists suggest that as Earth's tectonic plates moved over the mantle plume (also known as the Iceland plume), the plume created the Viluy Traps to the east during earlier periods, then the Siberian Traps during the Permian and Triassic periods. Later, it caused volcanic activity on the floor of the Arctic Ocean during the Jurassic and Cretaceous periods, and eventually led to volcanic activity in Iceland. Other tectonic processes may also have contributed. Another possible cause is the impact that formed the Wilkes Land crater in Antarctica, which is thought to have occurred around the same time and was located nearly opposite the Siberian Traps.
The main rock type in this formation is basalt, but mafic and felsic rocks are also present. Because of this mix, the formation is officially called a Flood Basalt Province. The presence of mafic and felsic rocks suggests that multiple eruptions occurred alongside the long series of eruptions that formed most of the basalt layers. The traps are divided into sections based on their chemical makeup, layering, and rock composition.
Beneath the Siberian Traps lies the Tungus Syneclise, a large sedimentary basin containing thick layers of carbonate and evaporite deposits from the Early-Mid Paleozoic era, as well as coal-bearing clastic rocks from the Carboniferous-Permian period. When heated, such as by igneous intrusions, these rocks can release large amounts of toxic and greenhouse gases.
Effects on prehistoric life
The Siberian Traps happened at the same time as the Permian–Triassic extinction event, which is the most severe extinction event ever recorded in Earth's history. Evidence from rocks, fossils, and chemical studies shows that this extinction was caused by a series of environmental changes. Eruptions from the Siberian Traps released large amounts of carbon dioxide, sulfur dioxide, halogens, and metals into the air. These emissions led to global warming, oxygen loss in the oceans, ocean acidification, reduced ozone in the atmosphere, acid rain, and toxic metal pollution. These changes caused widespread extinctions in both land and ocean ecosystems, though the timing of these effects differed slightly between land and sea. The timing of the massive volcanic activity and the extinction, along with the ability of this activity to produce large amounts of greenhouse gases, suggests that the Siberian Traps were the main cause of the extinction. However, scientists still debate why this extinction was so severe. Other possible causes or contributing factors have also been proposed.
Dating
The volcanism in the Siberian Traps caused large amounts of magma to be released from Earth's crust, leaving behind rocks from the same time as the mass extinction that can still be studied today. Zircon, a type of mineral, is found in some of these volcanic rocks. To determine the age of the zircon more accurately, scientists arranged different zircon samples into a timeline based on when they formed. The CA-TIMS technique, a method that removes differences in accuracy caused by lead loss over time, was then used to precisely measure the age of the zircons in the Siberian Traps. By focusing on uranium in the zircon, this technique helped scientists connect the volcanic activity in the Siberian Traps, which produced large amounts of magma, to the Permian–Triassic mass extinction.
To strengthen the link between the Siberian Traps and the Permian–Triassic extinction, scientists studied other events that occurred around the same time, such as changes in sea levels, meteor impacts, and volcanism. Focusing on volcanism, scientists collected and compared rock samples from the Siberian Traps and other southern regions. Basalt and gabbro samples from several southern areas near and far from the Siberian Traps were dated using the argon-argon method. Scientists used feldspar and biotite to determine the age of the samples and how long magma from the volcanic event remained present. Most of the basalt and gabbro samples were dated to 250 million years ago. They covered a surface area of 5,000,000 square kilometers (1,900,000 square miles) in the Siberian Traps and formed quickly with rapid cooling. Studies showed that basalt and gabbro samples from other southern regions from the same time period matched the age of samples in the Siberian Traps. This supports the idea that volcanic rocks from the Siberian Traps and other southern regions are connected to the Permian–Triassic mass extinction.
Mineral deposits
The giant Norilsk-Talnakh nickel-copper-palladium deposit formed inside the paths where magma moved in the most complete section of the Siberian Traps. Scientists have connected this deposit to the Permian-Triassic extinction event because large amounts of nickel and other elements were found in rock layers that formed after the extinction. Researchers compare the timeline of volcanic activity in the Siberian Traps with the timeline of the extinction event to link them. Before this connection was discovered, it was thought that the mass extinction and volcanic activity happened at the same time because of similarities in the composition of the rocks.