[Petrochemicals (OP)]

Are eruptions in volcanoes affected by the gravitational attraction of the moon and sun?

[chiralSPO]

Certainly! (but possibly not in the way that you are thinking).

I will point to Io as an example. This moon of Jupiter is the most volcanically active body in the solar system because of the tidal forces it experiences from Jupiter and the other Jovian moons. The constant tidal distortions heat the interior of the moon and drive its active geology.

Obviously this is an extreme example, and the Earth is much less tidally disrupted by the Moon and Sun. But I would bet that there is a nonzero contribution.

I don't know if there is any way to predict whether the tidal forces have ever been "the straw that broke the camel's back", but I would not be at all surprised if the constant tidal flexing has aided in the minor shifts and fissures that can lead up to an eruption.