Final answer:
The primary cause of a lava dome collapse is unstable overhanging topography, often due to gravitational forces on an overextended structure, and is amplified by earthquake vibrations. Volcanic eruptions and the geological activity at tectonic plate boundaries contribute to the processes that create and destabilize lava domes.
Step-by-step explanation:
What causes a growing lava dome to collapse? The primary cause of a lava dome collapse is unstable overhanging topography (A), which can occur when the lava dome grows beyond its stable structural limits, leading to a gravitational collapse. This instability can be exacerbated by factors such as steady magma supply or high volcanic pressure, but these are not the immediate causes of the collapse. Earthquake vibrations (D) also play a significant role in causing collapses, especially if the magma dome is already in a precarious state.
Within the context of plate tectonics, convergent boundaries where one plate subducts under another can lead to the creation of magma due to the release of water from hydrated minerals, contributing to conditions that produce and shape lava domes. Eruptions, such as those that formed Mount St. Helens, showcase the relation between dome-building eruptions and eventual dome collapse.
Other factors such as erosion by natural forces and excess weight from accumulation of materials can also contribute to the structural instability of lava domes. Volcanic eruptions, in particular, can generate loose materials that exacerbate the instability of a dome's slopes.