there is a finite amount of gold, but we don't know exactly how much that is, we could potentially find several big gold veins tomorrow and crash the gold market.

There is a finite amount of Bitcoin, and the amount of Bitcoin that will be injected into the market is deterministic by algorithm.

(Note that there are several old bitcoin wallets with "dead" bitcoins that could one day suddenly become active, which I suspect would have the same effect as finding a new goldmine)