* Astronomy

Title: ICE CORE AND PALAEOCLIMATIC EVIDENCE FOR THE TIMING AND NATURE OF THE GREAT MID-13TH CENTURY VOLCANIC ERUPTION
Authors: CLIVE OPPENHEIMER

Ice cores from both the Arctic and Antarctic record a massive volcanic eruption in around AD 1258. The inter-hemispheric transport of ash and sulphate aerosol suggests a low-latitude explosive eruption, but the volcano responsible is not known. This is remarkable given estimates of the magnitude of the event, which range up to 5 x 10^14 - 2 x 10^15 kg (~200 - 800 km³ of dense magma), which would make this the largest eruption of the historic period, and one of the very largest of the Holocene. The associated collapse caldera could have had a diameter up to 10 - 30 km. Palaeoclimate reconstructions indicate very cold austral and boreal summers in AD 1257 - 59, consistent with known patterns of continental summer cooling following tropical, sulphur-rich explosive eruptions. This suggests an eruption in AD 1257, producing a stronger climate forcing than hitherto recognised.

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The Mysterious Missing Eruption of 1258 A.D.

According to ice core and sediment core records from many places on the globe, there was a very large volcanic eruption in 1258 A.D. - so big that it injected somewhere between 190-270 megatonnes into the atmosphere.
Right now, it doesn't seem as if there is an obvious answer to the missing eruption of 1258 A.D. This isn't even the only missing large eruption in the ice/sediment core record. If you can believe it, there might have been a significant, possibly Pinatubo-scale eruption in 1809 that has not been identified. A quick look at the eruption record might finger VEI 4-5 eruptions at St. Helens in Washington, Soufriere St. Vincent in the West Indies and Awu in Indonesia but none seem to live up to the billing. It just shows how even for geologically recent eruptions, it can be difficult to pinpoint the source if all you have is the remote dusting of ash and aerosols that get trapped in ice possibly a hemisphere away from its source.
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