Why would they blow up the granite with dynamite?
If you want to build anything underground, you need to blow up the granite. That's simple. The folks who are building a large house near my home have been blasting the foundations for two weeks now.
But Vixen is really wrong when she claims that explosives are easily available in Finland.
Laki vaarallisten kemikaalien ja räjähteiden käsittelyn turvallisuudesta ("Law on safe handling of dangerous chemicals and explosives",
https://www.finlex.fi/fi/laki/ajantasa/2005/20050390) states that only three kinds of explosives can be handed over to private individuals:
1) fireworks that have been approved for private use
2) blank shells intended to be used with starter pistols
3) signal and illumination flares that have been approved
There's also the exception that ammunition may be handed over to people who have a licensed weapon.
The Panostajalaki ("Demolition certificate law",
https://www.finlex.fi/fi/laki/ajantasa/2016/20160423) then lists what certificates are needed for doing different demolition jobs.
[Edited to add: those are the current laws, back in 1994 the laws were essentially the same, but for example, a wider range of fireworks were considered appropriate for private use.]