Hmmmm. Looks like making there worlds biggest canon has zero downsides imho.

If pressure builds up we won't risk anything because the cement would just be propoulsed in the outter space and not hurt anyone.

congratulations: you have made a new volcano in a location much more difficult to predict

When Kilauea was making news for erupting, I showed my (now ex) partner a photo of the lava flow over the road with hazard barriers to keep people away.

Her response was to ask why they didn't just divert the flow away from where people are.

Duc(k/t) tape is cheaper

Why has noone ever experimented with placing a very large spaceship in the mouth of an active volcano? And when erupting, the space ship would fly to space without needing any fuel. No resources wasted on multiple stage rockets just to carry up fuel a few km, all that's needed is an enormous spaceship in the shape of a cement plug.

I just realised, that I first learned about pressure as a kid, when watching cartoon characters trying too stop a leak using body parts.

This creates a bomb, the interesting thing is does the cork or the side blow first

Big badda boom

Prevent harmful eruptions with one simple trick. Frees up more time for your other hobbies, like making pipe bombs.

The excellent podcast That's Absurd Please Elaborate answered this: https://thatsabsurdshow.com/episodes/005-scores-mutual-nightmares

TL;DL: big mistake, big boom

The people that get off watching those pimple popping videos on YouTube would literally NUT to this one weird TRICK

I'm sure Super Glue would work too.

Somebody didn't see those mount St Helens videos....