Final answer:
A volcano sector collapse can be triggered by several factors, with earthquakes being a particularly significant trigger as they result from tectonic plate movements.
Step-by-step explanation:
A volcano sector collapse may be triggered by a variety of factors, including earthquakes, which are the result of tectonic plates moving against each other. Sudden rainfall can add weight and weaken the structure of a volcanic edifice, and both the timing and intensity of an eruption can influence a collapse. However, the option that is explicitly mentioned and discussed within the reference material is earthquakes. Specifically, events like the 1980 eruption of Mt. St. Helens demonstrate how an earthquake can lead to a massive landslide and subsequent volcanic eruption, showcasing the dynamic relationship between these natural phenomena and their potential to trigger catastrophic events.