Final answer:
Pompeii was buried slowly under a thick layer of ash from a high-altitude ash column, which preserved structures and created body casts, while Herculaneum was rapidly buried by pyroclastic flows that preserved organic materials and offered a different type of preservation.
Step-by-step explanation:
Pompeii and Herculaneum experienced the eruption of Mount Vesuvius differently due to their locations relative to the volcano and the nature of the volcanic activity. In Pompeii, a thick blanket of ash fell over the city as a high-altitude ash column was expelled from Vesuvius. This ash fall lasted about six hours and buried the city under approximately 25 meters of tephra, preserving many structures and bodies in situ. The ash layer created casts that became crucial for archaeologists to understand the final moments of the city's inhabitants.
Conversely, Herculaneum suffered a different fate due to the pyroclastic flows—fast-moving waves of superheated gas and rock that petrified and preserved organic material. This intense heat carbonized wooden objects and even preserved bread loaves, offering a unique preservation that was not seen in Pompeii. Herculaneum was buried more rapidly by the pyroclastic flow, unlike the slower accumulation of ash in Pompeii. Therefore, while Pompeii offers insight into the urban environment during the Pax Romana, Herculaneum provides a detailed look into organic preservation under catastrophic conditions.