Pliny wrote the two letters describing the eruption of Mount Vesuvius approximately 25 years after the event, and both were sent in response to the request of his friend, the historian Tacitus, who wanted to know more about Pliny the Elder's death. The two letters have great historical value due to their accurate description of the Vesuvius eruption; Pliny's attention to detail in the letters about Vesuvius is so keen that modern volcanologists describe those types of eruptions as Plinian eruptions.