Final answer:
The start of the first stages of volcanic eruptions can be contested due to various factors such as limited eyewitness accounts, potential for unobserved early signs, and reinterpretation of data. Notably, the eruption of Mount Vesuvius is often dated to the afternoon of August 24, based on Pliny the Younger's account, but there could have been earlier signs.
Step-by-step explanation:
The first stages of volcanic eruptions vary depending on the specific event in question, and these can be contested for various reasons. For instance, the eruption of Mount Vesuvius, began on August 24, likely unnoticed early in the morning since Pliny the Younger did not observe signs until approximately 1:00 p.m. when a high-altitude column of ash was noticed. This timeline is contested because it's based on one eyewitness account and the possibility that there were earlier signs that were not observed or documented. Another example is from March 20, 1980, when a series of earthquakes indicated reawakening activity at Mount St. Helens, leading to an eruption that was observed and tracked closely by seismologists and geologists.
Contestation often arises due to limited observations, the potential for earlier unobserved signs of activity, reinterpretation of geological or historical data, or new scientific insights. For the Moon's volcanic activity, the debate on the onset of eruptions stems from the fact that much of the evidence from the first half billion years is lost, leading to a reliance on the geological record from after 3.3 billion years ago, when major mare volcanism ended.