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[Papewaio]

Not all metal is melted and cast. There is a whole industry based on manipulating hot iron and steel.

So steel bends as its gets hotter and at temperatures a person with a bellows can create using coal. Then using a hammer a person can generate enough force to bend steel.

This person is called a smith. It used to be such a common profession that one of the most common surnames is Smith.

Now take a hot temperature going for longer then used in a forge and apply not the pressure of a human wield hammer but the weight of twenty stories. Once it starts collapsing it would be a cascading failure as the momentum would add even more force. It goes from being a hammer used as a paper weight to one of a hammer being used to strike a blow as twenty plus stories collapse 3m onto the floor below and then they combine and collapse further with more speed and hence more energy.