page_title: Paleocene–Eocene Thermal Maximum
section_title: Volcanic activity
hierarchical_section_title: Paleocene–Eocene Thermal Maximum / Possible causes / Volcanic activity
context_page_description: The Paleocene–Eocene Thermal Maximum, alternatively "Eocene thermal maximum 1", and formerly known as the "Initial Eocene" or "Late Paleocene Thermal Maximum", was a time period with a more than 5–8 °C global average temperature rise across the event. This climate event occurred at the time boundary of the Paleocene and Eocene geological epochs. The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago.
  The associated period of massive carbon release into the atmosphere has been estimated to have lasted from 20,000 to 50,000 years. The entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C.
  The onset of the Paleocene–Eocene Thermal Maximum has been linked to volcanism and uplift associated with the North Atlantic Igneous Province, causing extreme changes in Earth's carbon cycle and a significant temperature rise. The period is marked by a prominent negative excursion in carbon stable isotope records from around the globe; more specifically, there was a large decrease in ¹³C/¹²C ratio of marine and terrestrial carbonates and organic carbon.
context_section_description: To balance the mass of carbon and produce the observed δ¹³C value, at least 1,500 gigatons of carbon would have to degas from the mantle via volcanoes over the course of the two, 1,000 year, steps. To put this in perspective, this is about 200 times the background rate of degassing for the rest of the Paleocene. There is no indication that such a burst of volcanic activity has occurred at any point in Earth's history. However, substantial volcanism had been active in East Greenland for around the preceding million years or so, but this struggles to explain the rapidity of the PETM. Even if the bulk of the 1,500 gigatons of carbon was released in a single pulse, further feedbacks would be necessary to produce the observed isotopic excursion.
  On the other hand, there are suggestions that surges of activity occurred in the later stages of the volcanism and associated continental rifting. Intrusions of hot magma into carbon-rich sediments may have triggered the degassing of isotopically light methane in sufficient volumes to cause global warming and the observed isotope anomaly. This hypothesis is documented by the presence of extensive intrusive sill complexes and thousands of kilometer-sized hydrothermal vent complexes in sedimentary basins on the mid-Norwegian margin and west of Shetland.  Volcanic eruptions of a large magnitude can impact global climate, reducing the amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns.  Large-scale volcanic activity may last only a few days, but the massive outpouring of gases and ash can influence climate patterns for years.  Sulfuric gases convert to sulfate aerosols, sub-micron droplets containing about 75 percent sulfuric acid. Following eruptions, these aerosol particles can linger as long as three to four years in the stratosphere.  
  Further phases of volcanic activity could have triggered the release of more methane, and caused other early Eocene warm events such as the ETM2.  
  It has also been suggested that volcanic activity around the Caribbean may have disrupted the circulation of oceanic currents, amplifying the magnitude of climate change.
  A 2017 study noted strong evidence of a volcanic carbon source (greater than 10,000 petagrams of carbon), associated with the North Atlantic Igneous Province.
caption: Satellite photo of Ardnamurchan – with clearly visible circular shape, which is the 'plumbings of an ancient volcano'
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