Scientists have identified a major volcanic eruption as a possible trigger for the Black Death that hit Europe in the mid-14th century. This eruption caused a cooling of the climate and crop failure, forcing the Italian states to import grain from the Black Sea region. It was these shipments that may have contained plague-infected fleas that carried the disease to Europe. The study used a combination of data from tree rings, ice cores and historical records to reconstruct the events leading up to the pandemic. This environmental factor set off a chain of events that resulted in the massive spread of the plague. The Black Death was caused by the bacterium Yersinia pestis, which could manifest itself in various forms, including the bubonic, pneumonic, and septicemic plagues. The probability of survival was very low, especially in the pneumonic form, where the mortality rate was almost 99%. This pandemic has had a significant impact on Europe's population, with some areas being hit harder than others.