Earthquake

Whenever you reach the bottom of the mine, you will find a Fissure that contains valuable ore.

Mining it will get you great rewards, but it also causes an Earthquake!

When the Earthquake is triggered, you'll have only a short time to get out of the mine, or else you will die and lose everything you brought with you. Items lost this way can't be retrieved, since the mine is regenerated after the earthquake is over!

The entire mine map will be lost and recreated at the end of the Earthquake, so make sure you mine everything you can and take out all the items you may have dropped before you attempt to mine the fissure.

On the plus side, triggering an Earthquake is a good way to go once you've mined most of the ore you're interested in from the mine. It may be time to mine the fissure and start fresh with this mine.

Each fissure produces a differend kind of special ore. The fissure at the bottom of the training mine will give you Granite, for example.