If there was a severe drop in hash power, the mining difficulty would also drop. If it dropped very low, a single computer using CPU mining would be enough to mine a block every ten minutes (as Satoshi himself did after he first created Bitcoin).

In the long run, as long as even a single person has an interesting in mining, a new block will be mined (on average) every ten minutes.

Difficulty adjustments happen ever 2016 blocks. Normally that is about once every 2 weeks. However with a large enough drop in hash power, that is a very long time.

> However with a large enough drop in hash power, that is a very long time.

We recently saw a 50% drop in hashrate. Bitcoin kept on producing blocks. https://www.theblockcrypto.com/post/109315/bitcoin-hashrate-...

Further, as miners turn their machines off, even before a difficulty adjustment, it becomes profitable (in btc terms) for those of us with ancient machines to resume mining. Our unprofitable machines suddenly become profitable.

> On a practical matter, a sudden drop in the value of bitcoin could make it literally impossible to buy.

Nope. Most buying happens on exchanges. The flood of liquidity wouldn't suddenly evaporate. And blocks would still be produced as explained above.

Btw. We've had ~90% drops in ₿ price before. https://twitter.com/ChartsBtc/status/1418395476190064645?s=1...