Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Mount St. Helens was a cone-shaped mountain that formed when molten material reached the surface of Earth and formed layers. Cone-shaped mountains form as a result of which one of these events?
volcanic eruptions
Volcanic eruption.